Merge tag 'i3c/for-7.3' of git://git.kernel.org/pub/scm/linux/kernel/git/i3c/linuxgrafted

Pull I3C updates from Alexandre Belloni:
 "A new driver this cycle, for the AMD AXI I3C controller.

  There are also new features such as IBI wakeup support, SETAASA device
  discovery and ACPI support for the the DAA methods, meaning we can now
  communicate with the SPD devices on DDR5 modules.

  New driver:
   - AMD AXI I3C master controller

  Subsystem:
   - I3C Common Command Code (CCC) handling improvements, especially
     around GET CCCs
   - SETAASA device discovery support
   - ACPI support for all existing DAA methods like SETDASA, SETNEWDA as
     well as I2C devices on I3C bus
   - IBI-based wakeup support

  Drivers:
   - dw: SETAASA support
   - mipi-i3c-hci: advertise IBI wakeup capability, AMD_PT I3C
     controller support, PIO queue management support for HCI v1.2
   - renesas: improve suspend to RAM support, add runtime PM support"

* tag 'i3c/for-7.3' of git://git.kernel.org/pub/scm/linux/kernel/git/i3c/linux: (70 commits)
  i3c: dw: reduce do_daa time if there's no client
  i3c: mipi-i3c-hci: Add support for AMD_PT I3C controller
  i3c: mipi-i3c-hci: Add PIO queue management support for HCI v1.2
  i3c: mipi-i3c-hci: Fix missing STAT_IBI_STATUS_THLD in PIO mode
  i3c: dw: rename "pclk" to "apb" to match dt-binding
  i3c: dw: make struct dw_i3c_cmd smaller
  i3c: dw: use COMMAND_PORT_TRANSFER_ARG instead of hardcoding
  i3c: renesas: Don't register devices when ENTDAA times out
  i3c: master: dw-i3c-master: fix OD timing for first broadcast
  i3c: mipi-i3c-hci: Advertise IBI wakeup capability
  i3c: mipi-i3c-hci: Factor out i3c_hci_sysdev()
  i3c: mipi-i3c-hci-pci: Propagate I3C wakeup requirements to PCI
  i3c: master: Reject IBI requests from non-IBI-capable devices
  i3c: master: Add helper to query bus wakeup requirements
  i3c: master: Report wakeup events for IBIs
  i3c: master: Support IBI-based wakeup capability
  i3c: master: Fix potential UAF in i3c_device_match()
  i3c: master: Fix potential UAF in i3c_device_uevent()
  i3c: Make dev->desc locking assumptions explicit
  i3c: master: Fix use-after-free of master->this
  ...

10 files changed, 2123 insertions, 0 deletions

diff --git a/Documentation/driver-api/driver-model/binding.rst b/Documentation/driver-api/driver-model/binding.rst
new file mode 100644
index 000000000..fa0888c2b
--- /dev/null
+++ b/Documentation/driver-api/driver-model/binding.rst
@@ -0,0 +1,149 @@
+==============
+Driver Binding
+==============
+
+Driver binding is the process of associating a device with a device
+driver that can control it. Bus drivers have typically handled this
+because there have been bus-specific structures to represent the
+devices and the drivers. With generic device and device driver
+structures, most of the binding can take place using common code.
+
+
+Bus
+~~~
+
+The bus type structure contains a list of all devices that are on that bus
+type in the system. When device_register is called for a device, it is
+inserted into the end of this list. The bus object also contains a
+list of all drivers of that bus type. When driver_register is called
+for a driver, it is inserted at the end of this list. These are the
+two events which trigger driver binding.
+
+
+device_register
+~~~~~~~~~~~~~~~
+
+When a new device is added, the bus's list of drivers is iterated over
+to find one that supports it. In order to determine that, the device
+ID of the device must match one of the device IDs that the driver
+supports. The format and semantics for comparing IDs is bus-specific.
+Instead of trying to derive a complex state machine and matching
+algorithm, it is up to the bus driver to provide a callback to compare
+a device against the IDs of a driver. The bus returns 1 if a match was
+found; 0 otherwise.
+
+int match(struct device * dev, struct device_driver * drv);
+
+If a match is found, the device's driver field is set to the driver
+and the driver's probe callback is called. This gives the driver a
+chance to verify that it really does support the hardware, and that
+it's in a working state.
+
+Device Class
+~~~~~~~~~~~~
+
+Upon the successful completion of probe, the device is registered with
+the class to which it belongs. Device drivers belong to one and only one
+class, and that is set in the driver's devclass field.
+devclass_add_device is called to enumerate the device within the class
+and actually register it with the class, which happens with the
+class's register_dev callback.
+
+
+Driver
+~~~~~~
+
+When a driver is attached to a device, the driver's probe() function is
+called. Within probe(), the driver initializes the device and allocates
+and initializes per-device data structures. This per-device state is
+associated with the device object for as long as the driver remains bound
+to it. Conceptually, this per-device data together with the binding to
+the device can be thought of as an instance of the driver.
+
+sysfs
+~~~~~
+
+A symlink is created in the bus's 'devices' directory that points to
+the device's directory in the physical hierarchy.
+
+A symlink is created in the driver's 'devices' directory that points
+to the device's directory in the physical hierarchy.
+
+A directory for the device is created in the class's directory. A
+symlink is created in that directory that points to the device's
+physical location in the sysfs tree.
+
+A symlink can be created (though this isn't done yet) in the device's
+physical directory to either its class directory, or the class's
+top-level directory. One can also be created to point to its driver's
+directory also.
+
+
+driver_register
+~~~~~~~~~~~~~~~
+
+The process is almost identical for when a new driver is added.
+The bus's list of devices is iterated over to find a match. Devices
+that already have a driver are skipped. All the devices are iterated
+over, to bind as many devices as possible to the driver.
+
+
+Removal
+~~~~~~~
+
+When a device is removed, the reference count for it will eventually
+go to 0. When it does, the remove callback of the driver is called. It
+is removed from the driver's list of devices and the reference count
+of the driver is decremented. All symlinks between the two are removed.
+
+When a driver is removed, the list of devices that it supports is
+iterated over, and the driver's remove callback is called for each
+one. The device is removed from that list and the symlinks removed.
+
+
+Driver Override
+~~~~~~~~~~~~~~~
+
+Userspace may override the standard matching by writing a driver name to
+a device's ``driver_override`` sysfs attribute.  When set, only a driver
+whose name matches the override will be considered during binding.  This
+bypasses all bus-specific matching (OF, ACPI, ID tables, etc.).
+
+The override may be cleared by writing an empty string, which returns
+the device to standard matching rules.  Writing to ``driver_override``
+does not automatically unbind the device from its current driver or
+make any attempt to load the specified driver.
+
+Buses opt into this mechanism by setting the ``driver_override`` flag in
+their ``struct bus_type``::
+
+  const struct bus_type example_bus_type = {
+      ...
+      .driver_override = true,
+  };
+
+When the flag is set, the driver core automatically creates the
+``driver_override`` sysfs attribute for every device on that bus.
+
+The bus's ``match()`` callback should check the override before performing
+its own matching, using ``device_match_driver_override()``::
+
+  static int example_match(struct device *dev, const struct device_driver *drv)
+  {
+      int ret;
+
+      ret = device_match_driver_override(dev, drv);
+      if (ret >= 0)
+          return ret;
+
+      /* Fall through to bus-specific matching... */
+  }
+
+``device_match_driver_override()`` returns > 0 if the override matches
+the given driver, 0 if the override is set but does not match, or < 0 if
+no override is set at all.
+
+Additional helpers are available:
+
+- ``device_set_driver_override()`` - set or clear the override from kernel code.
+- ``device_has_driver_override()`` - check whether an override is set.
diff --git a/Documentation/driver-api/driver-model/bus.rst b/Documentation/driver-api/driver-model/bus.rst
new file mode 100644
index 000000000..9709ab62a
--- /dev/null
+++ b/Documentation/driver-api/driver-model/bus.rst
@@ -0,0 +1,146 @@
+=========
+Bus Types
+=========
+
+Definition
+~~~~~~~~~~
+See the kerneldoc for the struct bus_type.
+
+int bus_register(struct bus_type * bus);
+
+
+Declaration
+~~~~~~~~~~~
+
+Each bus type in the kernel (PCI, USB, etc) should declare one static
+object of this type. They must initialize the name field, and may
+optionally initialize the match callback::
+
+   struct bus_type pci_bus_type = {
+          .name	= "pci",
+          .match	= pci_bus_match,
+   };
+
+The structure should be exported to drivers in a header file:
+
+extern struct bus_type pci_bus_type;
+
+
+Registration
+~~~~~~~~~~~~
+
+When a bus driver is initialized, it calls bus_register. This
+initializes the rest of the fields in the bus object and inserts it
+into a global list of bus types. Once the bus object is registered,
+the fields in it are usable by the bus driver.
+
+
+Callbacks
+~~~~~~~~~
+
+match(): Attaching Drivers to Devices
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The format of device ID structures and the semantics for comparing
+them are inherently bus-specific. Drivers typically declare an array
+of device IDs of devices they support that reside in a bus-specific
+driver structure.
+
+The purpose of the match callback is to give the bus an opportunity to
+determine if a particular driver supports a particular device by
+comparing the device IDs the driver supports with the device ID of a
+particular device, without sacrificing bus-specific functionality or
+type-safety.
+
+When a driver is registered with the bus, the bus's list of devices is
+iterated over, and the match callback is called for each device that
+does not have a driver associated with it.
+
+
+
+Device and Driver Lists
+~~~~~~~~~~~~~~~~~~~~~~~
+
+The lists of devices and drivers are intended to replace the local
+lists that many buses keep. They are lists of struct devices and
+struct device_drivers, respectively. Bus drivers are free to use the
+lists as they please, but conversion to the bus-specific type may be
+necessary.
+
+The LDM core provides helper functions for iterating over each list::
+
+  int bus_for_each_dev(struct bus_type * bus, struct device * start,
+		       void * data,
+		       int (*fn)(struct device *, void *));
+
+  int bus_for_each_drv(struct bus_type * bus, struct device_driver * start,
+		       void * data, int (*fn)(struct device_driver *, void *));
+
+These helpers iterate over the respective list, and call the callback
+for each device or driver in the list. All list accesses are
+synchronized by taking the bus's lock (read currently). The reference
+count on each object in the list is incremented before the callback is
+called; it is decremented after the next object has been obtained. The
+lock is not held when calling the callback.
+
+
+sysfs
+~~~~~~~~
+There is a top-level directory named 'bus'.
+
+Each bus gets a directory in the bus directory, along with two default
+directories::
+
+	/sys/bus/pci/
+	|-- devices
+	`-- drivers
+
+Drivers registered with the bus get a directory in the bus's drivers
+directory::
+
+	/sys/bus/pci/
+	|-- devices
+	`-- drivers
+	    |-- Intel ICH
+	    |-- Intel ICH Joystick
+	    |-- agpgart
+	    `-- e100
+
+Each device that is discovered on a bus of that type gets a symlink in
+the bus's devices directory to the device's directory in the physical
+hierarchy::
+
+	/sys/bus/pci/
+	|-- devices
+	|   |-- 00:00.0 -> ../../../root/pci0/00:00.0
+	|   |-- 00:01.0 -> ../../../root/pci0/00:01.0
+	|   `-- 00:02.0 -> ../../../root/pci0/00:02.0
+	`-- drivers
+
+
+Exporting Attributes
+~~~~~~~~~~~~~~~~~~~~
+
+::
+
+  struct bus_attribute {
+	struct attribute	attr;
+	ssize_t (*show)(const struct bus_type *, char * buf);
+	ssize_t (*store)(const struct bus_type *, const char * buf, size_t count);
+  };
+
+Bus drivers can export attributes using the BUS_ATTR_RW macro that works
+similarly to the DEVICE_ATTR_RW macro for devices. For example, a
+definition like this::
+
+	static BUS_ATTR_RW(debug);
+
+is equivalent to declaring::
+
+	static bus_attribute bus_attr_debug;
+
+This can then be used to add and remove the attribute from the bus's
+sysfs directory using::
+
+	int bus_create_file(struct bus_type *, struct bus_attribute *);
+	void bus_remove_file(struct bus_type *, struct bus_attribute *);
diff --git a/Documentation/driver-api/driver-model/design-patterns.rst b/Documentation/driver-api/driver-model/design-patterns.rst
new file mode 100644
index 000000000..965b2b93b
--- /dev/null
+++ b/Documentation/driver-api/driver-model/design-patterns.rst
@@ -0,0 +1,116 @@
+=============================
+Device Driver Design Patterns
+=============================
+
+This document describes a few common design patterns found in device drivers.
+It is likely that subsystem maintainers will ask driver developers to
+conform to these design patterns.
+
+1. State Container
+2. container_of()
+
+
+1. State Container
+~~~~~~~~~~~~~~~~~~
+
+While the kernel contains a few device drivers that assume that they will
+only be probed() once on a certain system (singletons), it is custom to assume
+that the device the driver binds to will appear in several instances. This
+means that the probe() function and all callbacks need to be reentrant.
+
+The most common way to achieve this is to use the state container design
+pattern. It usually has this form::
+
+  struct foo {
+      spinlock_t lock; /* Example member */
+      (...)
+  };
+
+  static int foo_probe(...)
+  {
+      struct foo *foo;
+
+      foo = devm_kzalloc(dev, sizeof(*foo), GFP_KERNEL);
+      if (!foo)
+          return -ENOMEM;
+      spin_lock_init(&foo->lock);
+      (...)
+  }
+
+This will create an instance of struct foo in memory every time probe() is
+called. This is our state container for this instance of the device driver.
+Of course it is then necessary to always pass this instance of the
+state around to all functions that need access to the state and its members.
+
+For example, if the driver is registering an interrupt handler, you would
+pass around a pointer to struct foo like this::
+
+  static irqreturn_t foo_handler(int irq, void *arg)
+  {
+      struct foo *foo = arg;
+      (...)
+  }
+
+  static int foo_probe(...)
+  {
+      struct foo *foo;
+
+      (...)
+      ret = request_irq(irq, foo_handler, 0, "foo", foo);
+  }
+
+This way you always get a pointer back to the correct instance of foo in
+your interrupt handler.
+
+
+2. container_of()
+~~~~~~~~~~~~~~~~~
+
+Continuing on the above example we add an offloaded work::
+
+  struct foo {
+      spinlock_t lock;
+      struct workqueue_struct *wq;
+      struct work_struct offload;
+      (...)
+  };
+
+  static void foo_work(struct work_struct *work)
+  {
+      struct foo *foo = container_of(work, struct foo, offload);
+
+      (...)
+  }
+
+  static irqreturn_t foo_handler(int irq, void *arg)
+  {
+      struct foo *foo = arg;
+
+      queue_work(foo->wq, &foo->offload);
+      (...)
+  }
+
+  static int foo_probe(...)
+  {
+      struct foo *foo;
+
+      foo->wq = create_singlethread_workqueue("foo-wq");
+      INIT_WORK(&foo->offload, foo_work);
+      (...)
+  }
+
+The design pattern is the same for an hrtimer or something similar that will
+return a single argument which is a pointer to a struct member in the
+callback.
+
+container_of() is a macro defined in <linux/container_of.h>
+
+What container_of() does is to obtain a pointer to the containing struct from
+a pointer to a member by a simple subtraction using the offsetof() macro from
+standard C, which allows something similar to object oriented behaviours.
+Notice that the contained member must not be a pointer, but an actual member
+for this to work.
+
+We can see here that we avoid having global pointers to our struct foo *
+instance this way, while still keeping the number of parameters passed to the
+work function to a single pointer.
diff --git a/Documentation/driver-api/driver-model/device.rst b/Documentation/driver-api/driver-model/device.rst
new file mode 100644
index 000000000..0833be568
--- /dev/null
+++ b/Documentation/driver-api/driver-model/device.rst
@@ -0,0 +1,120 @@
+==========================
+The Basic Device Structure
+==========================
+
+See the kerneldoc for the struct device.
+
+
+Programming Interface
+~~~~~~~~~~~~~~~~~~~~~
+The bus driver that discovers the device uses this to register the
+device with the core::
+
+  int device_register(struct device * dev);
+
+The bus should initialize the following fields:
+
+    - parent
+    - name
+    - bus_id
+    - bus
+
+A device is removed from the core when its reference count goes to
+0. The reference count can be adjusted using::
+
+  struct device * get_device(struct device * dev);
+  void put_device(struct device * dev);
+
+get_device() will return a pointer to the struct device passed to it
+if the reference is not already 0 (if it's in the process of being
+removed already).
+
+A driver can access the lock in the device structure using::
+
+  void lock_device(struct device * dev);
+  void unlock_device(struct device * dev);
+
+
+Attributes
+~~~~~~~~~~
+
+::
+
+  struct device_attribute {
+	struct attribute	attr;
+	ssize_t (*show)(struct device *dev, struct device_attribute *attr,
+			char *buf);
+	ssize_t (*store)(struct device *dev, struct device_attribute *attr,
+			 const char *buf, size_t count);
+  };
+
+Attributes of devices can be exported by a device driver through sysfs.
+
+Please see Documentation/filesystems/sysfs.rst for more information
+on how sysfs works.
+
+As explained in Documentation/core-api/kobject.rst, device attributes must be
+created before the KOBJ_ADD uevent is generated. The only way to realize
+that is by defining an attribute group.
+
+Attributes are declared using a macro called DEVICE_ATTR::
+
+  #define DEVICE_ATTR(name,mode,show,store)
+
+Example:::
+
+  static DEVICE_ATTR(type, 0444, type_show, NULL);
+  static DEVICE_ATTR(power, 0644, power_show, power_store);
+
+Helper macros are available for common values of mode, so the above examples
+can be simplified to:::
+
+  static DEVICE_ATTR_RO(type);
+  static DEVICE_ATTR_RW(power);
+
+This declares two structures of type struct device_attribute with respective
+names 'dev_attr_type' and 'dev_attr_power'. These two attributes can be
+organized as follows into a group::
+
+  static struct attribute *dev_attrs[] = {
+	&dev_attr_type.attr,
+	&dev_attr_power.attr,
+	NULL,
+  };
+
+  static struct attribute_group dev_group = {
+	.attrs = dev_attrs,
+  };
+
+  static const struct attribute_group *dev_groups[] = {
+	&dev_group,
+	NULL,
+  };
+
+A helper macro is available for the common case of a single group, so the
+above two structures can be declared using:::
+
+  ATTRIBUTE_GROUPS(dev);
+
+This array of groups can then be associated with a device by setting the
+group pointer in struct device before device_register() is invoked::
+
+        dev->groups = dev_groups;
+        device_register(dev);
+
+The device_register() function will use the 'groups' pointer to create the
+device attributes and the device_unregister() function will use this pointer
+to remove the device attributes.
+
+Word of warning:  While the kernel allows device_create_file() and
+device_remove_file() to be called on a device at any time, userspace has
+strict expectations on when attributes get created.  When a new device is
+registered in the kernel, a uevent is generated to notify userspace (like
+udev) that a new device is available.  If attributes are added after the
+device is registered, then userspace won't get notified and userspace will
+not know about the new attributes.
+
+This is important for device driver that need to publish additional
+attributes for a device at driver probe time.  If the device driver simply
+calls device_create_file() on the device structure passed to it, then
+userspace will never be notified of the new attributes.
diff --git a/Documentation/driver-api/driver-model/devres.rst b/Documentation/driver-api/driver-model/devres.rst
new file mode 100644
index 000000000..017fb155a
--- /dev/null
+++ b/Documentation/driver-api/driver-model/devres.rst
@@ -0,0 +1,470 @@
+================================
+Devres - Managed Device Resource
+================================
+
+Tejun Heo	<teheo@suse.de>
+
+First draft	10 January 2007
+
+.. contents
+
+   1. Intro			: Huh? Devres?
+   2. Devres			: Devres in a nutshell
+   3. Devres Group		: Group devres'es and release them together
+   4. Details			: Life time rules, calling context, ...
+   5. Overhead			: How much do we have to pay for this?
+   6. List of managed interfaces: Currently implemented managed interfaces
+
+
+1. Intro
+--------
+
+devres came up while trying to convert libata to use iomap.  Each
+iomapped address should be kept and unmapped on driver detach.  For
+example, a plain SFF ATA controller (that is, good old PCI IDE) in
+native mode makes use of 5 PCI BARs and all of them should be
+maintained.
+
+As with many other device drivers, libata low level drivers have
+sufficient bugs in ->remove and ->probe failure path.  Well, yes,
+that's probably because libata low level driver developers are lazy
+bunch, but aren't all low level driver developers?  After spending a
+day fiddling with braindamaged hardware with no document or
+braindamaged document, if it's finally working, well, it's working.
+
+For one reason or another, low level drivers don't receive as much
+attention or testing as core code, and bugs on driver detach or
+initialization failure don't happen often enough to be noticeable.
+Init failure path is worse because it's much less travelled while
+needs to handle multiple entry points.
+
+So, many low level drivers end up leaking resources on driver detach
+and having half broken failure path implementation in ->probe() which
+would leak resources or even cause oops when failure occurs.  iomap
+adds more to this mix.  So do msi and msix.
+
+
+2. Devres
+---------
+
+devres is basically linked list of arbitrarily sized memory areas
+associated with a struct device.  Each devres entry is associated with
+a release function.  A devres can be released in several ways.  No
+matter what, all devres entries are released on driver detach.  On
+release, the associated release function is invoked and then the
+devres entry is freed.
+
+Managed interface is created for resources commonly used by device
+drivers using devres.  For example, coherent DMA memory is acquired
+using dma_alloc_coherent().  The managed version is called
+dmam_alloc_coherent().  It is identical to dma_alloc_coherent() except
+for the DMA memory allocated using it is managed and will be
+automatically released on driver detach.  Implementation looks like
+the following::
+
+  struct dma_devres {
+	size_t		size;
+	void		*vaddr;
+	dma_addr_t	dma_handle;
+  };
+
+  static void dmam_coherent_release(struct device *dev, void *res)
+  {
+	struct dma_devres *this = res;
+
+	dma_free_coherent(dev, this->size, this->vaddr, this->dma_handle);
+  }
+
+  dmam_alloc_coherent(dev, size, dma_handle, gfp)
+  {
+	struct dma_devres *dr;
+	void *vaddr;
+
+	dr = devres_alloc(dmam_coherent_release, sizeof(*dr), gfp);
+	...
+
+	/* alloc DMA memory as usual */
+	vaddr = dma_alloc_coherent(...);
+	...
+
+	/* record size, vaddr, dma_handle in dr */
+	dr->vaddr = vaddr;
+	...
+
+	devres_add(dev, dr);
+
+	return vaddr;
+  }
+
+If a driver uses dmam_alloc_coherent(), the area is guaranteed to be
+freed whether initialization fails half-way or the device gets
+detached.  If most resources are acquired using managed interface, a
+driver can have much simpler init and exit code.  Init path basically
+looks like the following::
+
+  my_init_one()
+  {
+	struct mydev *d;
+
+	d = devm_kzalloc(dev, sizeof(*d), GFP_KERNEL);
+	if (!d)
+		return -ENOMEM;
+
+	d->ring = dmam_alloc_coherent(...);
+	if (!d->ring)
+		return -ENOMEM;
+
+	if (check something)
+		return -EINVAL;
+	...
+
+	return register_to_upper_layer(d);
+  }
+
+And exit path::
+
+  my_remove_one()
+  {
+	unregister_from_upper_layer(d);
+	shutdown_my_hardware();
+  }
+
+As shown above, low level drivers can be simplified a lot by using
+devres.  Complexity is shifted from less maintained low level drivers
+to better maintained higher layer.  Also, as init failure path is
+shared with exit path, both can get more testing.
+
+Note though that when converting current calls or assignments to
+managed devm_* versions it is up to you to check if internal operations
+like allocating memory, have failed. Managed resources pertains to the
+freeing of these resources *only* - all other checks needed are still
+on you. In some cases this may mean introducing checks that were not
+necessary before moving to the managed devm_* calls.
+
+
+3. Devres group
+---------------
+
+Devres entries can be grouped using devres group.  When a group is
+released, all contained normal devres entries and properly nested
+groups are released.  One usage is to rollback series of acquired
+resources on failure.  For example::
+
+  if (!devres_open_group(dev, NULL, GFP_KERNEL))
+	return -ENOMEM;
+
+  acquire A;
+  if (failed)
+	goto err;
+
+  acquire B;
+  if (failed)
+	goto err;
+  ...
+
+  devres_remove_group(dev, NULL);
+  return 0;
+
+ err:
+  devres_release_group(dev, NULL);
+  return err_code;
+
+As resource acquisition failure usually means probe failure, constructs
+like above are usually useful in midlayer driver (e.g. libata core
+layer) where interface function shouldn't have side effect on failure.
+For LLDs, just returning error code suffices in most cases.
+
+Each group is identified by `void *id`.  It can either be explicitly
+specified by @id argument to devres_open_group() or automatically
+created by passing NULL as @id as in the above example.  In both
+cases, devres_open_group() returns the group's id.  The returned id
+can be passed to other devres functions to select the target group.
+If NULL is given to those functions, the latest open group is
+selected.
+
+For example, you can do something like the following::
+
+  int my_midlayer_create_something()
+  {
+	if (!devres_open_group(dev, my_midlayer_create_something, GFP_KERNEL))
+		return -ENOMEM;
+
+	...
+
+	devres_close_group(dev, my_midlayer_create_something);
+	return 0;
+  }
+
+  void my_midlayer_destroy_something()
+  {
+	devres_release_group(dev, my_midlayer_create_something);
+  }
+
+
+4. Details
+----------
+
+Lifetime of a devres entry begins on devres allocation and finishes
+when it is released or destroyed (removed and freed) - no reference
+counting.
+
+devres core guarantees atomicity to all basic devres operations and
+has support for single-instance devres types (atomic
+lookup-and-add-if-not-found).  Other than that, synchronizing
+concurrent accesses to allocated devres data is caller's
+responsibility.  This is usually non-issue because bus ops and
+resource allocations already do the job.
+
+For an example of single-instance devres type, read pcim_iomap_table()
+in lib/devres.c.
+
+All devres interface functions can be called without context if the
+right gfp mask is given.
+
+
+5. Overhead
+-----------
+
+Each devres bookkeeping info is allocated together with requested data
+area.  With debug option turned off, bookkeeping info occupies 16
+bytes on 32bit machines and 24 bytes on 64bit (three pointers rounded
+up to ull alignment).  If singly linked list is used, it can be
+reduced to two pointers (8 bytes on 32bit, 16 bytes on 64bit).
+
+Each devres group occupies 8 pointers.  It can be reduced to 6 if
+singly linked list is used.
+
+Memory space overhead on ahci controller with two ports is between 300
+and 400 bytes on 32bit machine after naive conversion (we can
+certainly invest a bit more effort into libata core layer).
+
+
+6. List of managed interfaces
+-----------------------------
+
+CLOCK
+  devm_clk_get()
+  devm_clk_get_optional()
+  devm_clk_put()
+  devm_clk_bulk_get()
+  devm_clk_bulk_get_all()
+  devm_clk_bulk_get_optional()
+  devm_get_clk_from_child()
+  devm_clk_hw_register()
+  devm_of_clk_add_hw_provider()
+  devm_clk_hw_register_clkdev()
+
+DMA
+  dmaenginem_async_device_register()
+  dmam_alloc_coherent()
+  dmam_alloc_attrs()
+  dmam_free_coherent()
+  dmam_pool_create()
+  dmam_pool_destroy()
+
+DRM
+  devm_drm_dev_alloc()
+
+GPIO
+  devm_gpiod_get()
+  devm_gpiod_get_array()
+  devm_gpiod_get_array_optional()
+  devm_gpiod_get_index()
+  devm_gpiod_get_index_optional()
+  devm_gpiod_get_optional()
+  devm_gpiod_put()
+  devm_gpiod_unhinge()
+  devm_gpiochip_add_data()
+  devm_gpio_request_one()
+
+I2C
+  devm_i2c_add_adapter()
+  devm_i2c_new_dummy_device()
+
+IIO
+  devm_iio_device_alloc()
+  devm_iio_device_register()
+  devm_iio_dmaengine_buffer_setup()
+  devm_iio_kfifo_buffer_setup()
+  devm_iio_kfifo_buffer_setup_ext()
+  devm_iio_map_array_register()
+  devm_iio_triggered_buffer_setup()
+  devm_iio_triggered_buffer_setup_ext()
+  devm_iio_trigger_alloc()
+  devm_iio_trigger_register()
+  devm_iio_channel_get()
+  devm_iio_channel_get_all()
+  devm_iio_hw_consumer_alloc()
+  devm_fwnode_iio_channel_get_by_name()
+
+INPUT
+  devm_input_allocate_device()
+
+IO region
+  devm_release_mem_region()
+  devm_release_region()
+  devm_release_resource()
+  devm_request_mem_region()
+  devm_request_free_mem_region()
+  devm_request_region()
+  devm_request_resource()
+
+IOMAP
+  devm_ioport_map()
+  devm_ioport_unmap()
+  devm_ioremap()
+  devm_ioremap_uc()
+  devm_ioremap_wc()
+  devm_ioremap_resource() : checks resource, requests memory region, ioremaps
+  devm_ioremap_resource_wc()
+  devm_platform_ioremap_resource() : calls devm_ioremap_resource() for platform device
+  devm_platform_ioremap_resource_byname()
+  devm_platform_get_and_ioremap_resource()
+  devm_iounmap()
+
+  Note: For the PCI devices the specific pcim_*() functions may be used, see below.
+
+IRQ
+  devm_free_irq()
+  devm_request_any_context_irq()
+  devm_request_irq()
+  devm_request_threaded_irq()
+  devm_irq_alloc_descs()
+  devm_irq_alloc_desc()
+  devm_irq_alloc_desc_at()
+  devm_irq_alloc_desc_from()
+  devm_irq_alloc_descs_from()
+  devm_irq_alloc_generic_chip()
+  devm_irq_setup_generic_chip()
+  devm_irq_domain_create_sim()
+
+LED
+  devm_led_classdev_register()
+  devm_led_classdev_register_ext()
+  devm_led_classdev_unregister()
+  devm_led_trigger_register()
+  devm_of_led_get()
+
+MDIO
+  devm_mdiobus_alloc()
+  devm_mdiobus_alloc_size()
+  devm_mdiobus_register()
+  devm_of_mdiobus_register()
+
+MEM
+  devm_free_pages()
+  devm_get_free_pages()
+  devm_kasprintf()
+  devm_kcalloc()
+  devm_kfree()
+  devm_kmalloc()
+  devm_kmalloc_array()
+  devm_kmemdup()
+  devm_krealloc()
+  devm_krealloc_array()
+  devm_kstrdup()
+  devm_kstrdup_const()
+  devm_kvasprintf()
+  devm_kzalloc()
+
+MFD
+  devm_mfd_add_devices()
+
+MUX
+  devm_mux_chip_alloc()
+  devm_mux_chip_register()
+  devm_mux_control_get()
+  devm_mux_state_get()
+
+NET
+  devm_alloc_etherdev()
+  devm_alloc_etherdev_mqs()
+  devm_register_netdev()
+
+PER-CPU MEM
+  devm_alloc_percpu()
+
+PCI
+  devm_pci_alloc_host_bridge()  : managed PCI host bridge allocation
+  devm_pci_remap_cfgspace()	: ioremap PCI configuration space
+  devm_pci_remap_cfg_resource()	: ioremap PCI configuration space resource
+
+  pcim_enable_device()		: after success, the PCI device gets disabled automatically on driver detach
+  pcim_iomap()			: do iomap() on a single BAR
+  pcim_iomap_regions()		: do request_region() and iomap() on multiple BARs
+  pcim_iomap_table()		: array of mapped addresses indexed by BAR
+  pcim_iounmap()		: do iounmap() on a single BAR
+  pcim_pin_device()		: keep PCI device enabled after release
+  pcim_set_mwi()		: enable Memory-Write-Invalidate PCI transaction
+
+PHY
+  devm_usb_get_phy()
+  devm_usb_get_phy_by_node()
+  devm_usb_get_phy_by_phandle()
+
+PINCTRL
+  devm_pinctrl_get()
+  devm_pinctrl_put()
+  devm_pinctrl_get_select()
+  devm_pinctrl_register()
+  devm_pinctrl_register_and_init()
+
+POWER
+  devm_reboot_mode_register()
+  devm_reboot_mode_unregister()
+
+PWM
+  devm_pwmchip_alloc()
+  devm_pwmchip_add()
+  devm_pwm_get()
+  devm_fwnode_pwm_get()
+
+REGULATOR
+  devm_regulator_bulk_register_supply_alias()
+  devm_regulator_bulk_get()
+  devm_regulator_bulk_get_const()
+  devm_regulator_bulk_get_enable()
+  devm_regulator_bulk_put()
+  devm_regulator_get()
+  devm_regulator_get_enable()
+  devm_regulator_get_enable_read_voltage()
+  devm_regulator_get_enable_optional()
+  devm_regulator_get_exclusive()
+  devm_regulator_get_optional()
+  devm_regulator_irq_helper()
+  devm_regulator_put()
+  devm_regulator_register()
+  devm_regulator_register_notifier()
+  devm_regulator_register_supply_alias()
+  devm_regulator_unregister_notifier()
+
+RESET
+  devm_reset_control_get()
+  devm_reset_controller_register()
+
+RTC
+  devm_rtc_device_register()
+  devm_rtc_allocate_device()
+  devm_rtc_register_device()
+  devm_rtc_nvmem_register()
+
+SERDEV
+  devm_serdev_device_open()
+
+SLAVE DMA ENGINE
+  devm_acpi_dma_controller_register()
+
+SPI
+  devm_spi_alloc_host()
+  devm_spi_alloc_target()
+  devm_spi_optimize_message()
+  devm_spi_register_controller()
+  devm_spi_register_host()
+  devm_spi_register_target()
+
+WATCHDOG
+  devm_watchdog_register_device()
+
+WORKQUEUE
+  devm_alloc_workqueue()
+  devm_alloc_ordered_workqueue()
diff --git a/Documentation/driver-api/driver-model/driver.rst b/Documentation/driver-api/driver-model/driver.rst
new file mode 100644
index 000000000..06f818b1d
--- /dev/null
+++ b/Documentation/driver-api/driver-model/driver.rst
@@ -0,0 +1,286 @@
+==============
+Device Drivers
+==============
+
+See the kerneldoc for the struct device_driver.
+
+Allocation
+~~~~~~~~~~
+
+Device drivers are statically allocated structures. Though there may
+be multiple devices in a system that a driver supports, struct
+device_driver represents the driver as a whole (not a particular
+device instance).
+
+Initialization
+~~~~~~~~~~~~~~
+
+The driver must initialize at least the name and bus fields. It should
+also initialize the devclass field (when it arrives), so it may obtain
+the proper linkage internally. It should also initialize as many of
+the callbacks as possible, though each is optional.
+
+Declaration
+~~~~~~~~~~~
+
+As stated above, struct device_driver objects are statically
+allocated. Below is an example declaration of the eepro100
+driver. This declaration is hypothetical only; it relies on the driver
+being converted completely to the new model::
+
+  static struct device_driver eepro100_driver = {
+         .name		= "eepro100",
+         .bus		= &pci_bus_type,
+
+         .probe		= eepro100_probe,
+         .remove		= eepro100_remove,
+         .suspend		= eepro100_suspend,
+         .resume		= eepro100_resume,
+  };
+
+Most drivers will not be able to be converted completely to the new
+model because the bus they belong to has a bus-specific structure with
+bus-specific fields that cannot be generalized.
+
+The most common example of this are device ID structures. A driver
+typically defines an array of device IDs that it supports. The format
+of these structures and the semantics for comparing device IDs are
+completely bus-specific. Defining them as bus-specific entities would
+sacrifice type-safety, so we keep bus-specific structures around.
+
+Bus-specific drivers should include a generic struct device_driver in
+the definition of the bus-specific driver. Like this::
+
+  struct pci_driver {
+         const struct pci_device_id *id_table;
+         struct device_driver	  driver;
+  };
+
+A definition that included bus-specific fields would look like
+(using the eepro100 driver again)::
+
+  static struct pci_driver eepro100_driver = {
+         .id_table       = eepro100_pci_tbl,
+         .driver	       = {
+		.name		= "eepro100",
+		.bus		= &pci_bus_type,
+		.probe		= eepro100_probe,
+		.remove		= eepro100_remove,
+		.suspend	= eepro100_suspend,
+		.resume		= eepro100_resume,
+         },
+  };
+
+Some may find the syntax of embedded struct initialization awkward or
+even a bit ugly. So far, it's the best way we've found to do what we want...
+
+Registration
+~~~~~~~~~~~~
+
+::
+
+  int driver_register(struct device_driver *drv);
+
+The driver registers the structure on startup. For drivers that have
+no bus-specific fields (i.e. don't have a bus-specific driver
+structure), they would use driver_register and pass a pointer to their
+struct device_driver object.
+
+Most drivers, however, will have a bus-specific structure and will
+need to register with the bus using something like pci_driver_register.
+
+It is important that drivers register their driver structure as early as
+possible. Registration with the core initializes several fields in the
+struct device_driver object, including the reference count and the
+lock. These fields are assumed to be valid at all times and may be
+used by the device model core or the bus driver.
+
+
+Transition Bus Drivers
+~~~~~~~~~~~~~~~~~~~~~~
+
+By defining wrapper functions, the transition to the new model can be
+made easier. Drivers can ignore the generic structure altogether and
+let the bus wrapper fill in the fields. For the callbacks, the bus can
+define generic callbacks that forward the call to the bus-specific
+callbacks of the drivers.
+
+This solution is intended to be only temporary. In order to get class
+information in the driver, the drivers must be modified anyway. Since
+converting drivers to the new model should reduce some infrastructural
+complexity and code size, it is recommended that they are converted as
+class information is added.
+
+Access
+~~~~~~
+
+Once the object has been registered, it may access the common fields of
+the object, like the lock and the list of devices::
+
+  int driver_for_each_dev(struct device_driver *drv, void *data,
+			  int (*callback)(struct device *dev, void *data));
+
+The devices field is a list of all the devices that have been bound to
+the driver. The LDM core provides a helper function to operate on all
+the devices a driver controls. This helper locks the driver on each
+node access, and does proper reference counting on each device as it
+accesses it.
+
+
+sysfs
+~~~~~
+
+When a driver is registered, a sysfs directory is created in its
+bus's directory. In this directory, the driver can export an interface
+to userspace to control operation of the driver on a global basis;
+e.g. toggling debugging output in the driver.
+
+A future feature of this directory will be a 'devices' directory. This
+directory will contain symlinks to the directories of devices it
+supports.
+
+
+
+Callbacks
+~~~~~~~~~
+
+::
+
+	int	(*probe)	(struct device *dev);
+
+The probe() entry is called in task context, with the bus's rwsem locked
+and the driver partially bound to the device.  Drivers commonly use
+container_of() to convert "dev" to a bus-specific type, both in probe()
+and other routines.  That type often provides device resource data, such
+as pci_dev.resource[] or platform_device.resources, which is used in
+addition to dev->platform_data to initialize the driver.
+
+This callback holds the driver-specific logic to bind the driver to a
+given device.  That includes verifying that the device is present, that
+it's a version the driver can handle, that driver data structures can
+be allocated and initialized, and that any hardware can be initialized.
+Drivers often store a pointer to their state with dev_set_drvdata().
+When the driver has successfully bound itself to that device, then probe()
+returns zero and the driver model code will finish its part of binding
+the driver to that device.
+
+A driver's probe() may return a negative errno value to indicate that
+the driver did not bind to this device, in which case it should have
+released all resources it allocated.
+
+Optionally, probe() may return -EPROBE_DEFER if the driver depends on
+resources that are not yet available (e.g., supplied by a driver that
+hasn't initialized yet).  The driver core will put the device onto the
+deferred probe list and will try to call it again later. If a driver
+must defer, it should return -EPROBE_DEFER as early as possible to
+reduce the amount of time spent on setup work that will need to be
+unwound and reexecuted at a later time.
+
+.. warning::
+      -EPROBE_DEFER must not be returned if probe() has already created
+      child devices, even if those child devices are removed again
+      in a cleanup path. If -EPROBE_DEFER is returned after a child
+      device has been registered, it may result in an infinite loop of
+      .probe() calls to the same driver.
+
+::
+
+	void	(*sync_state)	(struct device *dev);
+
+sync_state is called only once for a device. It's called when all the consumer
+devices of the device have successfully probed. The list of consumers of the
+device is obtained by looking at the device links connecting that device to its
+consumer devices.
+
+The first attempt to call sync_state() is made during late_initcall_sync() to
+give firmware and drivers time to link devices to each other. During the first
+attempt at calling sync_state(), if all the consumers of the device at that
+point in time have already probed successfully, sync_state() is called right
+away. If there are no consumers of the device during the first attempt, that
+too is considered as "all consumers of the device have probed" and sync_state()
+is called right away.
+
+If during the first attempt at calling sync_state() for a device, there are
+still consumers that haven't probed successfully, the sync_state() call is
+postponed and reattempted in the future only when one or more consumers of the
+device probe successfully. If during the reattempt, the driver core finds that
+there are one or more consumers of the device that haven't probed yet, then
+sync_state() call is postponed again.
+
+A typical use case for sync_state() is to have the kernel cleanly take over
+management of devices from the bootloader. For example, if a device is left on
+and at a particular hardware configuration by the bootloader, the device's
+driver might need to keep the device in the boot configuration until all the
+consumers of the device have probed. Once all the consumers of the device have
+probed, the device's driver can synchronize the hardware state of the device to
+match the aggregated software state requested by all the consumers. Hence the
+name sync_state().
+
+While obvious examples of resources that can benefit from sync_state() include
+resources such as regulator, sync_state() can also be useful for complex
+resources like IOMMUs. For example, IOMMUs with multiple consumers (devices
+whose addresses are remapped by the IOMMU) might need to keep their mappings
+fixed at (or additive to) the boot configuration until all its consumers have
+probed.
+
+While the typical use case for sync_state() is to have the kernel cleanly take
+over management of devices from the bootloader, the usage of sync_state() is
+not restricted to that. Use it whenever it makes sense to take an action after
+all the consumers of a device have probed::
+
+	int 	(*remove)	(struct device *dev);
+
+remove is called to unbind a driver from a device. This may be
+called if a device is physically removed from the system, if the
+driver module is being unloaded, during a reboot sequence, or
+in other cases.
+
+It is up to the driver to determine if the device is present or
+not. It should free any resources allocated specifically for the
+device; i.e. anything in the device's driver_data field.
+
+If the device is still present, it should quiesce the device and place
+it into a supported low-power state.
+
+::
+
+	int	(*suspend)	(struct device *dev, pm_message_t state);
+
+suspend is called to put the device in a low power state.
+
+::
+
+	int	(*resume)	(struct device *dev);
+
+Resume is used to bring a device back from a low power state.
+
+
+Attributes
+~~~~~~~~~~
+
+::
+
+  struct driver_attribute {
+          struct attribute        attr;
+          ssize_t (*show)(struct device_driver *driver, char *buf);
+          ssize_t (*store)(struct device_driver *, const char *buf, size_t count);
+  };
+
+Device drivers can export attributes via their sysfs directories.
+Drivers can declare attributes using a DRIVER_ATTR_RW and DRIVER_ATTR_RO
+macro that works identically to the DEVICE_ATTR_RW and DEVICE_ATTR_RO
+macros.
+
+Example::
+
+	DRIVER_ATTR_RW(debug);
+
+This is equivalent to declaring::
+
+	struct driver_attribute driver_attr_debug;
+
+This can then be used to add and remove the attribute from the
+driver's directory using::
+
+  int driver_create_file(struct device_driver *, const struct driver_attribute *);
+  void driver_remove_file(struct device_driver *, const struct driver_attribute *);
diff --git a/Documentation/driver-api/driver-model/index.rst b/Documentation/driver-api/driver-model/index.rst
new file mode 100644
index 000000000..abeb4b366
--- /dev/null
+++ b/Documentation/driver-api/driver-model/index.rst
@@ -0,0 +1,16 @@
+============
+Driver Model
+============
+
+.. toctree::
+   :maxdepth: 1
+
+   binding
+   bus
+   design-patterns
+   device
+   devres
+   driver
+   overview
+   platform
+   porting
diff --git a/Documentation/driver-api/driver-model/overview.rst b/Documentation/driver-api/driver-model/overview.rst
new file mode 100644
index 000000000..b3f447bf9
--- /dev/null
+++ b/Documentation/driver-api/driver-model/overview.rst
@@ -0,0 +1,124 @@
+=============================
+The Linux Kernel Device Model
+=============================
+
+Patrick Mochel	<mochel@digitalimplant.org>
+
+Drafted 26 August 2002
+Updated 31 January 2006
+
+
+Overview
+~~~~~~~~
+
+The Linux Kernel Driver Model is a unification of all the disparate driver
+models that were previously used in the kernel. It is intended to augment the
+bus-specific drivers for bridges and devices by consolidating a set of data
+and operations into globally accessible data structures.
+
+Traditional driver models implemented some sort of tree-like structure
+(sometimes just a list) for the devices they control. There wasn't any
+uniformity across the different bus types.
+
+The current driver model provides a common, uniform data model for describing
+a bus and the devices that can appear under the bus. The unified bus
+model includes a set of common attributes which all buses carry, and a set
+of common callbacks, such as device discovery during bus probing, bus
+shutdown, bus power management, etc.
+
+The common device and bridge interface reflects the goals of the modern
+computer: namely the ability to do seamless device "plug and play", power
+management, and hot plug. In particular, the model dictated by Intel and
+Microsoft (namely ACPI) ensures that almost every device on almost any bus
+on an x86-compatible system can work within this paradigm.  Of course,
+not every bus is able to support all such operations, although most
+buses support most of those operations.
+
+
+Downstream Access
+~~~~~~~~~~~~~~~~~
+
+Common data fields have been moved out of individual bus layers into a common
+data structure. These fields must still be accessed by the bus layers,
+and sometimes by the device-specific drivers.
+
+Other bus layers are encouraged to do what has been done for the PCI layer.
+struct pci_dev now looks like this::
+
+  struct pci_dev {
+	...
+
+	struct device dev;     /* Generic device interface */
+	...
+  };
+
+Note first that the struct device dev within the struct pci_dev is
+statically allocated. This means only one allocation on device discovery.
+
+Note also that that struct device dev is not necessarily defined at the
+front of the pci_dev structure.  This is to make people think about what
+they're doing when switching between the bus driver and the global driver,
+and to discourage meaningless and incorrect casts between the two.
+
+The PCI bus layer freely accesses the fields of struct device. It knows about
+the structure of struct pci_dev, and it should know the structure of struct
+device. Individual PCI device drivers that have been converted to the current
+driver model generally do not and should not touch the fields of struct device,
+unless there is a compelling reason to do so.
+
+The above abstraction prevents unnecessary pain during transitional phases.
+If it were not done this way, then when a field was renamed or removed, every
+downstream driver would break.  On the other hand, if only the bus layer
+(and not the device layer) accesses the struct device, it is only the bus
+layer that needs to change.
+
+
+User Interface
+~~~~~~~~~~~~~~
+
+By virtue of having a complete hierarchical view of all the devices in the
+system, exporting a complete hierarchical view to userspace becomes relatively
+easy. This has been accomplished by implementing a special purpose virtual
+file system named sysfs.
+
+Almost all mainstream Linux distros mount this filesystem automatically; you
+can see some variation of the following in the output of the "mount" command::
+
+  $ mount
+  ...
+  none on /sys type sysfs (rw,noexec,nosuid,nodev)
+  ...
+  $
+
+The auto-mounting of sysfs is typically accomplished by an entry similar to
+the following in the /etc/fstab file::
+
+  none     	/sys	sysfs    defaults	  	0 0
+
+or something similar in the /lib/init/fstab file on Debian-based systems::
+
+  none            /sys    sysfs    nodev,noexec,nosuid    0 0
+
+If sysfs is not automatically mounted, you can always do it manually with::
+
+	# mount -t sysfs sysfs /sys
+
+Whenever a device is inserted into the tree, a directory is created for it.
+This directory may be populated at each layer of discovery - the global layer,
+the bus layer, or the device layer.
+
+The global layer currently creates two files - 'name' and 'power'. The
+former only reports the name of the device. The latter reports the
+current power state of the device. It will also be used to set the current
+power state.
+
+The bus layer may also create files for the devices it finds while probing the
+bus. For example, the PCI layer currently creates 'irq' and 'resource' files
+for each PCI device.
+
+A device-specific driver may also export files in its directory to expose
+device-specific data or tunable interfaces.
+
+More information about the sysfs directory layout can be found in
+the other documents in this directory and in the file
+Documentation/filesystems/sysfs.rst.
diff --git a/Documentation/driver-api/driver-model/platform.rst b/Documentation/driver-api/driver-model/platform.rst
new file mode 100644
index 000000000..9673470bd
--- /dev/null
+++ b/Documentation/driver-api/driver-model/platform.rst
@@ -0,0 +1,248 @@
+============================
+Platform Devices and Drivers
+============================
+
+See <linux/platform_device.h> for the driver model interface to the
+platform bus:  platform_device, and platform_driver.  This pseudo-bus
+is used to connect devices on buses with minimal infrastructure,
+like those used to integrate peripherals on many system-on-chip
+processors, or some "legacy" PC interconnects; as opposed to large
+formally specified ones like PCI or USB.
+
+
+Platform devices
+~~~~~~~~~~~~~~~~
+Platform devices are devices that typically appear as autonomous
+entities in the system. This includes legacy port-based devices and
+host bridges to peripheral buses, and most controllers integrated
+into system-on-chip platforms.  What they usually have in common
+is direct addressing from a CPU bus.  Rarely, a platform_device will
+be connected through a segment of some other kind of bus; but its
+registers will still be directly addressable.
+
+Platform devices are given a name, used in driver binding, and a
+list of resources such as addresses and IRQs::
+
+  struct platform_device {
+	const char	*name;
+	u32		id;
+	struct device	dev;
+	u32		num_resources;
+	struct resource	*resource;
+  };
+
+
+Platform drivers
+~~~~~~~~~~~~~~~~
+Platform drivers follow the standard driver model convention, where
+discovery/enumeration is handled outside the drivers, and drivers
+provide probe() and remove() methods.  They support power management
+and shutdown notifications using the standard conventions::
+
+  struct platform_driver {
+	int (*probe)(struct platform_device *);
+	void (*remove)(struct platform_device *);
+	void (*shutdown)(struct platform_device *);
+	int (*suspend)(struct platform_device *, pm_message_t state);
+	int (*resume)(struct platform_device *);
+	struct device_driver driver;
+	const struct platform_device_id *id_table;
+	bool prevent_deferred_probe;
+	bool driver_managed_dma;
+  };
+
+Note that probe() should in general verify that the specified device hardware
+actually exists; sometimes platform setup code can't be sure.  The probing
+can use device resources, including clocks, and device platform_data.
+
+Platform drivers register themselves the normal way::
+
+	int platform_driver_register(struct platform_driver *drv);
+
+Or, in common situations where the device is known not to be hot-pluggable,
+the probe() routine can live in an init section to reduce the driver's
+runtime memory footprint::
+
+	int platform_driver_probe(struct platform_driver *drv,
+			  int (*probe)(struct platform_device *))
+
+Kernel modules can be composed of several platform drivers. The platform core
+provides helpers to register and unregister an array of drivers::
+
+	int __platform_register_drivers(struct platform_driver * const *drivers,
+				      unsigned int count, struct module *owner,
+				      const char *mod_name);
+	void platform_unregister_drivers(struct platform_driver * const *drivers,
+					 unsigned int count);
+
+If one of the drivers fails to register, all drivers registered up to that
+point will be unregistered in reverse order. Note that there is a convenience
+macro that passes THIS_MODULE as owner parameter::
+
+	#define platform_register_drivers(drivers, count)
+
+
+Device Enumeration
+~~~~~~~~~~~~~~~~~~
+As a rule, platform specific (and often board-specific) setup code will
+register platform devices::
+
+	int platform_device_register(struct platform_device *pdev);
+
+	int platform_add_devices(struct platform_device **pdevs, int ndev);
+
+The general rule is to register only those devices that actually exist,
+but in some cases extra devices might be registered.  For example, a kernel
+might be configured to work with an external network adapter that might not
+be populated on all boards, or likewise to work with an integrated controller
+that some boards might not hook up to any peripherals.
+
+In some cases, boot firmware will export tables describing the devices
+that are populated on a given board.   Without such tables, often the
+only way for system setup code to set up the correct devices is to build
+a kernel for a specific target board.  Such board-specific kernels are
+common with embedded and custom systems development.
+
+In many cases, the memory and IRQ resources associated with the platform
+device are not enough to let the device's driver work.  Board setup code
+will often provide additional information using the device's platform_data
+field to hold additional information.
+
+Embedded systems frequently need one or more clocks for platform devices,
+which are normally kept off until they're actively needed (to save power).
+System setup also associates those clocks with the device, so that
+calls to clk_get(&pdev->dev, clock_name) return them as needed.
+
+
+Legacy Drivers:  Device Probing
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Some drivers are not fully converted to the driver model, because they take
+on a non-driver role:  the driver registers its platform device, rather than
+leaving that for system infrastructure.  Such drivers can't be hotplugged
+or coldplugged, since those mechanisms require device creation to be in a
+different system component than the driver.
+
+The only "good" reason for this is to handle older system designs which, like
+original IBM PCs, rely on error-prone "probe-the-hardware" models for hardware
+configuration.  Newer systems have largely abandoned that model, in favor of
+bus-level support for dynamic configuration (PCI, USB), or device tables
+provided by the boot firmware (e.g. PNPACPI on x86).  There are too many
+conflicting options about what might be where, and even educated guesses by
+an operating system will be wrong often enough to make trouble.
+
+This style of driver is discouraged.  If you're updating such a driver,
+please try to move the device enumeration to a more appropriate location,
+outside the driver.  This will usually be cleanup, since such drivers
+tend to already have "normal" modes, such as ones using device nodes that
+were created by PNP or by platform device setup.
+
+None the less, there are some APIs to support such legacy drivers.  Avoid
+using these calls except with such hotplug-deficient drivers::
+
+	struct platform_device *platform_device_alloc(
+			const char *name, int id);
+
+You can use platform_device_alloc() to dynamically allocate a device, which
+you will then initialize with resources and platform_device_register().
+A better solution is usually::
+
+	struct platform_device *platform_device_register_simple(
+			const char *name, int id,
+			struct resource *res, unsigned int nres);
+
+You can use platform_device_register_simple() as a one-step call to allocate
+and register a device.
+
+
+Device Naming and Driver Binding
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The platform_device.dev.bus_id is the canonical name for the devices.
+It's built from two components:
+
+    * platform_device.name ... which is also used to for driver matching.
+
+    * platform_device.id ... the device instance number, or else "-1"
+      to indicate there's only one.
+
+These are concatenated, so name/id "serial"/0 indicates bus_id "serial.0", and
+"serial/3" indicates bus_id "serial.3"; both would use the platform_driver
+named "serial".  While "my_rtc"/-1 would be bus_id "my_rtc" (no instance id)
+and use the platform_driver called "my_rtc".
+
+Driver binding is performed automatically by the driver core, invoking
+driver probe() after finding a match between device and driver.  If the
+probe() succeeds, the driver and device are bound as usual.  There are
+three different ways to find such a match:
+
+    - Whenever a device is registered, the drivers for that bus are
+      checked for matches.  Platform devices should be registered very
+      early during system boot.
+
+    - When a driver is registered using platform_driver_register(), all
+      unbound devices on that bus are checked for matches.  Drivers
+      usually register later during booting, or by module loading.
+
+    - Registering a driver using platform_driver_probe() works just like
+      using platform_driver_register(), except that the driver won't
+      be probed later if another device registers.  (Which is OK, since
+      this interface is only for use with non-hotpluggable devices.)
+
+
+Early Platform Devices and Drivers
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The early platform interfaces provide platform data to platform device
+drivers early on during the system boot. The code is built on top of the
+early_param() command line parsing and can be executed very early on.
+
+Example: "earlyprintk" class early serial console in 6 steps
+
+1. Registering early platform device data
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The architecture code registers platform device data using the function
+early_platform_add_devices(). In the case of early serial console this
+should be hardware configuration for the serial port. Devices registered
+at this point will later on be matched against early platform drivers.
+
+2. Parsing kernel command line
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The architecture code calls parse_early_param() to parse the kernel
+command line. This will execute all matching early_param() callbacks.
+User specified early platform devices will be registered at this point.
+For the early serial console case the user can specify port on the
+kernel command line as "earlyprintk=serial.0" where "earlyprintk" is
+the class string, "serial" is the name of the platform driver and
+0 is the platform device id. If the id is -1 then the dot and the
+id can be omitted.
+
+3. Installing early platform drivers belonging to a certain class
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The architecture code may optionally force registration of all early
+platform drivers belonging to a certain class using the function
+early_platform_driver_register_all(). User specified devices from
+step 2 have priority over these. This step is omitted by the serial
+driver example since the early serial driver code should be disabled
+unless the user has specified port on the kernel command line.
+
+4. Early platform driver registration
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Compiled-in platform drivers making use of early_platform_init() are
+automatically registered during step 2 or 3. The serial driver example
+should use early_platform_init("earlyprintk", &platform_driver).
+
+5. Probing of early platform drivers belonging to a certain class
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The architecture code calls early_platform_driver_probe() to match
+registered early platform devices associated with a certain class with
+registered early platform drivers. Matched devices will get probed().
+This step can be executed at any point during the early boot. As soon
+as possible may be good for the serial port case.
+
+6. Inside the early platform driver probe()
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The driver code needs to take special care during early boot, especially
+when it comes to memory allocation and interrupt registration. The code
+in the probe() function can use is_early_platform_device() to check if
+it is called at early platform device or at the regular platform device
+time. The early serial driver performs register_console() at this point.
+
+For further information, see <linux/platform_device.h>.
diff --git a/Documentation/driver-api/driver-model/porting.rst b/Documentation/driver-api/driver-model/porting.rst
new file mode 100644
index 000000000..931ea879a
--- /dev/null
+++ b/Documentation/driver-api/driver-model/porting.rst
@@ -0,0 +1,448 @@
+=======================================
+Porting Drivers to the New Driver Model
+=======================================
+
+Patrick Mochel
+
+7 January 2003
+
+
+Overview
+
+Please refer to `Documentation/driver-api/driver-model/*.rst` for definitions of
+various driver types and concepts.
+
+Most of the work of porting devices drivers to the new model happens
+at the bus driver layer. This was intentional, to minimize the
+negative effect on kernel drivers, and to allow a gradual transition
+of bus drivers.
+
+In a nutshell, the driver model consists of a set of objects that can
+be embedded in larger, bus-specific objects. Fields in these generic
+objects can replace fields in the bus-specific objects.
+
+The generic objects must be registered with the driver model core. By
+doing so, they will exported via the sysfs filesystem. sysfs can be
+mounted by doing::
+
+	# mount -t sysfs sysfs /sys
+
+
+
+The Process
+
+Step 0: Read include/linux/device.h for object and function definitions.
+
+Step 1: Registering the bus driver.
+
+
+- Define a struct bus_type for the bus driver::
+
+    struct bus_type pci_bus_type = {
+          .name           = "pci",
+    };
+
+
+- Register the bus type.
+
+  This should be done in the initialization function for the bus type,
+  which is usually the module_init(), or equivalent, function::
+
+    static int __init pci_driver_init(void)
+    {
+            return bus_register(&pci_bus_type);
+    }
+
+    subsys_initcall(pci_driver_init);
+
+
+  The bus type may be unregistered (if the bus driver may be compiled
+  as a module) by doing::
+
+     bus_unregister(&pci_bus_type);
+
+
+- Export the bus type for others to use.
+
+  Other code may wish to reference the bus type, so declare it in a
+  shared header file and export the symbol.
+
+From include/linux/pci.h::
+
+  extern struct bus_type pci_bus_type;
+
+
+From file the above code appears in::
+
+  EXPORT_SYMBOL(pci_bus_type);
+
+
+
+- This will cause the bus to show up in /sys/bus/pci/ with two
+  subdirectories: 'devices' and 'drivers'::
+
+    # tree -d /sys/bus/pci/
+    /sys/bus/pci/
+    |-- devices
+    `-- drivers
+
+
+
+Step 2: Registering Devices.
+
+struct device represents a single device. It mainly contains metadata
+describing the relationship the device has to other entities.
+
+
+- Embed a struct device in the bus-specific device type::
+
+
+    struct pci_dev {
+           ...
+           struct  device  dev;            /* Generic device interface */
+           ...
+    };
+
+  It is recommended that the generic device not be the first item in
+  the struct to discourage programmers from doing mindless casts
+  between the object types. Instead macros, or inline functions,
+  should be created to convert from the generic object type::
+
+
+    #define to_pci_dev(n) container_of(n, struct pci_dev, dev)
+
+    or
+
+    static inline struct pci_dev * to_pci_dev(struct kobject * kobj)
+    {
+	return container_of(n, struct pci_dev, dev);
+    }
+
+  This allows the compiler to verify type-safety of the operations
+  that are performed (which is Good).
+
+
+- Initialize the device on registration.
+
+  When devices are discovered or registered with the bus type, the
+  bus driver should initialize the generic device. The most important
+  things to initialize are the bus_id, parent, and bus fields.
+
+  The bus_id is an ASCII string that contains the device's address on
+  the bus. The format of this string is bus-specific. This is
+  necessary for representing devices in sysfs.
+
+  parent is the physical parent of the device. It is important that
+  the bus driver sets this field correctly.
+
+  The driver model maintains an ordered list of devices that it uses
+  for power management. This list must be in order to guarantee that
+  devices are shutdown before their physical parents, and vice versa.
+  The order of this list is determined by the parent of registered
+  devices.
+
+  Also, the location of the device's sysfs directory depends on a
+  device's parent. sysfs exports a directory structure that mirrors
+  the device hierarchy. Accurately setting the parent guarantees that
+  sysfs will accurately represent the hierarchy.
+
+  The device's bus field is a pointer to the bus type the device
+  belongs to. This should be set to the bus_type that was declared
+  and initialized before.
+
+  Optionally, the bus driver may set the device's name and release
+  fields.
+
+  The name field is an ASCII string describing the device, like
+
+     "ATI Technologies Inc Radeon QD"
+
+  The release field is a callback that the driver model core calls
+  when the device has been removed, and all references to it have
+  been released. More on this in a moment.
+
+
+- Register the device.
+
+  Once the generic device has been initialized, it can be registered
+  with the driver model core by doing::
+
+       device_register(&dev->dev);
+
+  It can later be unregistered by doing::
+
+       device_unregister(&dev->dev);
+
+  This should happen on buses that support hotpluggable devices.
+  If a bus driver unregisters a device, it should not immediately free
+  it. It should instead wait for the driver model core to call the
+  device's release method, then free the bus-specific object.
+  (There may be other code that is currently referencing the device
+  structure, and it would be rude to free the device while that is
+  happening).
+
+
+  When the device is registered, a directory in sysfs is created.
+  The PCI tree in sysfs looks like::
+
+    /sys/devices/pci0/
+    |-- 00:00.0
+    |-- 00:01.0
+    |   `-- 01:00.0
+    |-- 00:02.0
+    |   `-- 02:1f.0
+    |       `-- 03:00.0
+    |-- 00:1e.0
+    |   `-- 04:04.0
+    |-- 00:1f.0
+    |-- 00:1f.1
+    |   |-- ide0
+    |   |   |-- 0.0
+    |   |   `-- 0.1
+    |   `-- ide1
+    |       `-- 1.0
+    |-- 00:1f.2
+    |-- 00:1f.3
+    `-- 00:1f.5
+
+  Also, symlinks are created in the bus's 'devices' directory
+  that point to the device's directory in the physical hierarchy::
+
+    /sys/bus/pci/devices/
+    |-- 00:00.0 -> ../../../devices/pci0/00:00.0
+    |-- 00:01.0 -> ../../../devices/pci0/00:01.0
+    |-- 00:02.0 -> ../../../devices/pci0/00:02.0
+    |-- 00:1e.0 -> ../../../devices/pci0/00:1e.0
+    |-- 00:1f.0 -> ../../../devices/pci0/00:1f.0
+    |-- 00:1f.1 -> ../../../devices/pci0/00:1f.1
+    |-- 00:1f.2 -> ../../../devices/pci0/00:1f.2
+    |-- 00:1f.3 -> ../../../devices/pci0/00:1f.3
+    |-- 00:1f.5 -> ../../../devices/pci0/00:1f.5
+    |-- 01:00.0 -> ../../../devices/pci0/00:01.0/01:00.0
+    |-- 02:1f.0 -> ../../../devices/pci0/00:02.0/02:1f.0
+    |-- 03:00.0 -> ../../../devices/pci0/00:02.0/02:1f.0/03:00.0
+    `-- 04:04.0 -> ../../../devices/pci0/00:1e.0/04:04.0
+
+
+
+Step 3: Registering Drivers.
+
+struct device_driver is a simple driver structure that contains a set
+of operations that the driver model core may call.
+
+
+- Embed a struct device_driver in the bus-specific driver.
+
+  Just like with devices, do something like::
+
+    struct pci_driver {
+           ...
+           struct device_driver    driver;
+    };
+
+
+- Initialize the generic driver structure.
+
+  When the driver registers with the bus (e.g. doing pci_register_driver()),
+  initialize the necessary fields of the driver: the name and bus
+  fields.
+
+
+- Register the driver.
+
+  After the generic driver has been initialized, call::
+
+	driver_register(&drv->driver);
+
+  to register the driver with the core.
+
+  When the driver is unregistered from the bus, unregister it from the
+  core by doing::
+
+        driver_unregister(&drv->driver);
+
+  Note that this will block until all references to the driver have
+  gone away. Normally, there will not be any.
+
+
+- Sysfs representation.
+
+  Drivers are exported via sysfs in their bus's 'driver's directory.
+  For example::
+
+    /sys/bus/pci/drivers/
+    |-- 3c59x
+    |-- Ensoniq AudioPCI
+    |-- agpgart-amdk7
+    |-- e100
+    `-- serial
+
+
+Step 4: Define Generic Methods for Drivers.
+
+struct device_driver defines a set of operations that the driver model
+core calls. Most of these operations are probably similar to
+operations the bus already defines for drivers, but taking different
+parameters.
+
+It would be difficult and tedious to force every driver on a bus to
+simultaneously convert their drivers to generic format. Instead, the
+bus driver should define single instances of the generic methods that
+forward call to the bus-specific drivers. For instance::
+
+
+  static int pci_device_remove(struct device * dev)
+  {
+          struct pci_dev * pci_dev = to_pci_dev(dev);
+          struct pci_driver * drv = pci_dev->driver;
+
+          if (drv) {
+                  if (drv->remove)
+                          drv->remove(pci_dev);
+                  pci_dev->driver = NULL;
+          }
+          return 0;
+  }
+
+
+The generic driver should be initialized with these methods before it
+is registered::
+
+        /* initialize common driver fields */
+        drv->driver.name = drv->name;
+        drv->driver.bus = &pci_bus_type;
+        drv->driver.probe = pci_device_probe;
+        drv->driver.resume = pci_device_resume;
+        drv->driver.suspend = pci_device_suspend;
+        drv->driver.remove = pci_device_remove;
+
+        /* register with core */
+        driver_register(&drv->driver);
+
+
+Ideally, the bus should only initialize the fields if they are not
+already set. This allows the drivers to implement their own generic
+methods.
+
+
+Step 5: Support generic driver binding.
+
+The model assumes that a device or driver can be dynamically
+registered with the bus at any time. When registration happens,
+devices must be bound to a driver, or drivers must be bound to all
+devices that it supports.
+
+A driver typically contains a list of device IDs that it supports. The
+bus driver compares these IDs to the IDs of devices registered with it.
+The format of the device IDs, and the semantics for comparing them are
+bus-specific, so the generic model does attempt to generalize them.
+
+Instead, a bus may supply a method in struct bus_type that does the
+comparison::
+
+  int (*match)(struct device * dev, struct device_driver * drv);
+
+match should return positive value if the driver supports the device,
+and zero otherwise. It may also return error code (for example
+-EPROBE_DEFER) if determining that given driver supports the device is
+not possible.
+
+When a device is registered, the bus's list of drivers is iterated
+over. bus->match() is called for each one until a match is found.
+
+When a driver is registered, the bus's list of devices is iterated
+over. bus->match() is called for each device that is not already
+claimed by a driver.
+
+When a device is successfully bound to a driver, device->driver is
+set, the device is added to a per-driver list of devices, and a
+symlink is created in the driver's sysfs directory that points to the
+device's physical directory::
+
+  /sys/bus/pci/drivers/
+  |-- 3c59x
+  |   `-- 00:0b.0 -> ../../../../devices/pci0/00:0b.0
+  |-- Ensoniq AudioPCI
+  |-- agpgart-amdk7
+  |   `-- 00:00.0 -> ../../../../devices/pci0/00:00.0
+  |-- e100
+  |   `-- 00:0c.0 -> ../../../../devices/pci0/00:0c.0
+  `-- serial
+
+
+This driver binding should replace the existing driver binding
+mechanism the bus currently uses.
+
+
+Step 6: Supply a hotplug callback.
+
+Whenever a device is registered with the driver model core, the
+userspace program /sbin/hotplug is called to notify userspace.
+Users can define actions to perform when a device is inserted or
+removed.
+
+The driver model core passes several arguments to userspace via
+environment variables, including
+
+- ACTION: set to 'add' or 'remove'
+- DEVPATH: set to the device's physical path in sysfs.
+
+A bus driver may also supply additional parameters for userspace to
+consume. To do this, a bus must implement the 'hotplug' method in
+struct bus_type::
+
+     int (*hotplug) (struct device *dev, char **envp,
+                     int num_envp, char *buffer, int buffer_size);
+
+This is called immediately before /sbin/hotplug is executed.
+
+
+Step 7: Cleaning up the bus driver.
+
+The generic bus, device, and driver structures provide several fields
+that can replace those defined privately to the bus driver.
+
+- Device list.
+
+struct bus_type contains a list of all devices registered with the bus
+type. This includes all devices on all instances of that bus type.
+An internal list that the bus uses may be removed, in favor of using
+this one.
+
+The core provides an iterator to access these devices::
+
+  int bus_for_each_dev(struct bus_type * bus, struct device * start,
+                       void * data, int (*fn)(struct device *, void *));
+
+
+- Driver list.
+
+struct bus_type also contains a list of all drivers registered with
+it. An internal list of drivers that the bus driver maintains may
+be removed in favor of using the generic one.
+
+The drivers may be iterated over, like devices::
+
+  int bus_for_each_drv(struct bus_type * bus, struct device_driver * start,
+                       void * data, int (*fn)(struct device_driver *, void *));
+
+
+Please see drivers/base/bus.c for more information.
+
+
+- rwsem
+
+struct bus_type contains an rwsem that protects all core accesses to
+the device and driver lists. This can be used by the bus driver
+internally, and should be used when accessing the device or driver
+lists the bus maintains.
+
+
+- Device and driver fields.
+
+Some of the fields in struct device and struct device_driver duplicate
+fields in the bus-specific representations of these objects. Feel free
+to remove the bus-specific ones and favor the generic ones. Note
+though, that this will likely mean fixing up all the drivers that
+reference the bus-specific fields (though those should all be 1-line
+changes).