Merge tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Fix error output of boot instance creation failure

   Currently if a boot instance creation fails, instead of printing out
   the name of the instance that failed, it prints "(null)". That is
   because it prints "cur_str" that had already been processed by
   strsep(). Print the saved name instead.

   While at it, print the error code of the failure.

 - Fix use-after-free for same named historgrams

   Histograms can be named so that they can be used in multiple events.
   But if the named histogram has a variable attached, the second event
   that uses the named histogram which duplicates it and needs to free
   the original after duplication leaves the old variable in place and
   still visible. If another histogram uses than variable, it will use
   the stale one which will try to reference the freed duplicate
   histogram and crash the kernel.

   Free the duplicate variables along with the duplicated histogram
   data.

 - Check return value of kthread_run() in event self test

   The events self tests uses a kthread for testing but does not check
   if it succeeded in creating a kthread. If the kthread creation were
   to fail, the code will still try to call kthread_stop() on the error
   returned.

 - Fix race between reading trace_pipe and updating subbuffer size

   If a user is reading the trace_pipe file at the same time they update
   the ring buffer sub-buffer size, can cause the trace_pipe read to
   read stale data. Add trace_access_lock() around updating the ring
   buffer sub-buffer size.

 - Fix eventfs_inode on failure path in creation of the events directory

   In the creation of the "events" directory, if after allocating the
   eventfs_inode a failure is detected, it calls cleanup_ei() which
   calls free_ei(). The free_ei() will test if eventfs_inode being freed
   has no children. It is a bug if it does. But on the failure case of
   the creation of the "events" directory, the children lists have not
   yet been initialized and the free will trigger a warning because
   list_empty() on an uninitialized list returns false.

   Move the initialization into init_ei() where it makes more sense and
   makes sure that a created eventfs_inode has its lists initialized
   upon creation.

 - Check return value of kthread_run() in ftrace direct sample code

   The sample code that shows how to use the ftrace direct calls does
   not test the return of kthread_run() to see if it succeeds. Return a
   failure if the kthread_run() doesn't succeed.

 - Clear user events state on fork in case of alloc failure

   On fork, the child gets a pointer to the parent's user events state.
   It makes a copy of it then updates the child's pointer to it. But if
   the allocation fails, the duplication function leaves the child with
   a pointer to its parent's descriptor. When the child cleans up its
   data, it will free the parent's descriptor while the parent is still
   using it.

   In the duplication function, set the child's user_event_mm to NULL
   before testing if the allocation succeeded, and when it exits it will
   not free the parent's descriptor.

 - Fix retry exhaustion in simple ring buffer reader swap

   simple_ring_buffer_swap_reader_page() starts with retry set to 8 and
   post-decrements it only after a failed link replacement. On the final
   attempt, a successful replacement leaves retry at zero, while a
   failed replacement leaves it at -1.

   But the check for success expects the retry value to be non-zero and
   exits with an error on zero. This is the opposite result. Fix it.

 - Fail nicely when the remote swap_reader_page() returns an error

   Currently, if the swap_reader_page() of a remote buffer fails, it
   triggers a WARN_ON_ONCE() and continues normally. Instead, have it
   exit with an error and a pr_warn() print instead of a full WARNING.

* tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  ring-buffer: Stop remote reader update when page swap fails
  tracing: Fix retry exhaustion in simple ring buffer reader swap
  tracing/user_events: Clear copied tracing state before fork duplication
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-modify
  eventfs: Initialize ei->children and ei->list in init_ei()
  tracing: Fix use-after-free in trace_pipe read on sub-buffer order change
  tracing: Fix crash passing ERR_PTR to kthread_stop()
  tracing: Fix use-after-free with same-name named triggers
  tracing: Fix logged instance name on creation failure

1 files changed, 200 insertions, 0 deletions

diff --git a/Documentation/driver-api/soundwire/summary.rst b/Documentation/driver-api/soundwire/summary.rst
new file mode 100644
index 000000000..df7805374
--- /dev/null
+++ b/Documentation/driver-api/soundwire/summary.rst
@@ -0,0 +1,200 @@
+===========================
+SoundWire Subsystem Summary
+===========================
+
+SoundWire is a new interface ratified in 2015 by the MIPI Alliance.
+SoundWire is used for transporting data typically related to audio
+functions. SoundWire interface is optimized to integrate audio devices in
+mobile or mobile inspired systems.
+
+SoundWire is a 2-pin multi-drop interface with data and clock line. It
+facilitates development of low cost, efficient, high performance systems.
+Broad level key features of SoundWire interface include:
+
+ (1) Transporting all of payload data channels, control information, and setup
+     commands over a single two-pin interface.
+
+ (2) Lower clock frequency, and hence lower power consumption, by use of DDR
+     (Dual Data Rate) data transmission.
+
+ (3) Clock scaling and optional multiple data lanes to give wide flexibility
+     in data rate to match system requirements.
+
+ (4) Device status monitoring, including interrupt-style alerts to the Master.
+
+The SoundWire protocol supports up to eleven Slave interfaces. All the
+interfaces share the common Bus containing data and clock line. Each of the
+Slaves can support up to 14 Data Ports. 13 Data Ports are dedicated to audio
+transport. Data Port0 is dedicated to transport of Bulk control information,
+each of the audio Data Ports (1..14) can support up to 8 Channels in
+transmit or receiving mode (typically fixed direction but configurable
+direction is enabled by the specification).  Bandwidth restrictions to
+~19.2..24.576Mbits/s don't however allow for 11*13*8 channels to be
+transmitted simultaneously.
+
+Below figure shows an example of connectivity between a SoundWire Master and
+two Slave devices. ::
+
+        +---------------+                                       +---------------+
+        |               |                       Clock Signal    |               |
+        |    Master     |-------+-------------------------------|    Slave      |
+        |   Interface   |       |               Data Signal     |  Interface 1  |
+        |               |-------|-------+-----------------------|               |
+        +---------------+       |       |                       +---------------+
+                                |       |
+                                |       |
+                                |       |
+                             +--+-------+--+
+                             |             |
+                             |   Slave     |
+                             | Interface 2 |
+                             |             |
+                             +-------------+
+
+
+Terminology
+===========
+
+The MIPI SoundWire specification uses the term 'device' to refer to a Master
+or Slave interface, which of course can be confusing. In this summary and
+code we use the term interface only to refer to the hardware. We follow the
+Linux device model by mapping each Slave interface connected on the bus as a
+device managed by a specific driver. The Linux SoundWire subsystem provides
+a framework to implement a SoundWire Slave driver with an API allowing
+3rd-party vendors to enable implementation-defined functionality while
+common setup/configuration tasks are handled by the bus.
+
+Bus:
+Implements SoundWire Linux Bus which handles the SoundWire protocol.
+Programs all the MIPI-defined Slave registers. Represents a SoundWire
+Master. Multiple instances of Bus may be present in a system.
+
+Slave:
+Registers as SoundWire Slave device (Linux Device). Multiple Slave devices
+can register to a Bus instance.
+
+Slave driver:
+Driver controlling the Slave device. MIPI-specified registers are controlled
+directly by the Bus (and transmitted through the Master driver/interface).
+Any implementation-defined Slave register is controlled by Slave driver. In
+practice, it is expected that the Slave driver relies on regmap and does not
+request direct register access.
+
+Programming interfaces (SoundWire Master interface Driver)
+==========================================================
+
+SoundWire Bus supports programming interfaces for the SoundWire Master
+implementation and SoundWire Slave devices. All the code uses the "sdw"
+prefix commonly used by SoC designers and 3rd party vendors.
+
+Each of the SoundWire Master interfaces needs to be registered to the Bus.
+Bus implements API to read standard Master MIPI properties and also provides
+callback in Master ops for Master driver to implement its own functions that
+provides capabilities information. DT support is not implemented at this
+time but should be trivial to add since capabilities are enabled with the
+``device_property_`` API.
+
+The Master interface along with the Master interface capabilities are
+registered based on board file, DT or ACPI.
+
+Following is the Bus API to register the SoundWire Bus:
+
+.. code-block:: c
+
+	int sdw_bus_master_add(struct sdw_bus *bus,
+				struct device *parent,
+				struct fwnode_handle)
+	{
+		sdw_master_device_add(bus, parent, fwnode);
+
+		mutex_init(&bus->lock);
+		INIT_LIST_HEAD(&bus->slaves);
+
+		/* Check ACPI for Slave devices */
+		sdw_acpi_find_slaves(bus);
+
+		/* Check DT for Slave devices */
+		sdw_of_find_slaves(bus);
+
+		return 0;
+	}
+
+This will initialize sdw_bus object for Master device. "sdw_master_ops" and
+"sdw_master_port_ops" callback functions are provided to the Bus.
+
+"sdw_master_ops" is used by Bus to control the Bus in the hardware specific
+way. It includes Bus control functions such as sending the SoundWire
+read/write messages on Bus, setting up clock frequency & Stream
+Synchronization Point (SSP). The "sdw_master_ops" structure abstracts the
+hardware details of the Master from the Bus.
+
+"sdw_master_port_ops" is used by Bus to setup the Port parameters of the
+Master interface Port. Master interface Port register map is not defined by
+MIPI specification, so Bus calls the "sdw_master_port_ops" callback
+function to do Port operations like "Port Prepare", "Port Transport params
+set", "Port enable and disable". The implementation of the Master driver can
+then perform hardware-specific configurations.
+
+Programming interfaces (SoundWire Slave Driver)
+===============================================
+
+The MIPI specification requires each Slave interface to expose a unique
+48-bit identifier, stored in 6 read-only dev_id registers. This dev_id
+identifier contains vendor and part information, as well as a field enabling
+to differentiate between identical components. An additional class field is
+currently unused. Slave driver is written for a specific vendor and part
+identifier, Bus enumerates the Slave device based on these two ids.
+Slave device and driver match is done based on these two ids . Probe
+of the Slave driver is called by Bus on successful match between device and
+driver id. A parent/child relationship is enforced between Master and Slave
+devices (the logical representation is aligned with the physical
+connectivity).
+
+The information on Master/Slave dependencies is stored in platform data,
+board-file, ACPI or DT. The MIPI Software specification defines additional
+link_id parameters for controllers that have multiple Master interfaces. The
+dev_id registers are only unique in the scope of a link, and the link_id
+unique in the scope of a controller. Both dev_id and link_id are not
+necessarily unique at the system level but the parent/child information is
+used to avoid ambiguity.
+
+.. code-block:: c
+
+	static const struct sdw_device_id slave_id[] = {
+	        SDW_SLAVE_ENTRY(0x025d, 0x700, 0),
+	        {},
+	};
+	MODULE_DEVICE_TABLE(sdw, slave_id);
+
+	static struct sdw_driver slave_sdw_driver = {
+	        .driver = {
+	                   .name = "slave_xxx",
+	                   .pm = &slave_runtime_pm,
+	                   },
+		.probe = slave_sdw_probe,
+		.remove = slave_sdw_remove,
+		.ops = &slave_slave_ops,
+		.id_table = slave_id,
+	};
+
+
+For capabilities, Bus implements API to read standard Slave MIPI properties
+and also provides callback in Slave ops for Slave driver to implement own
+function that provides capabilities information. Bus needs to know a set of
+Slave capabilities to program Slave registers and to control the Bus
+reconfigurations.
+
+Links
+=====
+
+SoundWire MIPI specification 1.1 is available at:
+https://members.mipi.org/wg/All-Members/document/70290
+
+SoundWire MIPI DisCo (Discovery and Configuration) specification is
+available at:
+https://www.mipi.org/specifications/mipi-disco-soundwire
+
+(publicly accessible with registration or directly accessible to MIPI
+members)
+
+MIPI Alliance Manufacturer ID Page: mid.mipi.org