Merge tag 'trace-v7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Don't destroy user event fields when removal fails

   User event fields are destroyed before the event is removed from
   visibility. But that can fail leaving the still visible event with no
   fields. Move the destroying of the fields to after the event is
   successfully removed from visibility.

 - Initialize function graph state is fork before calling
   copy_exec_state()

   For non-CLONE_VM forks, copy_exec_state() allocates a new
   task_exec_state. If that allocation fails, ftrace_graph_exit_task()
   will free the tasks ret_stack pointer. Since that pointer is still
   using the parent's ret_stack, it mistakenly frees the parent's
   pointer too.

   Call ftrace_graph_init() on the task first which will NULL out the
   new tasks's ret_stack and if the copy fails, it will not free
   anything.

 - Remove FGRAPH_MAX_INDEX

   The macro FGRAPH_MAX_INDEX was added but never used. Remove it.

 - Save ent_size in function graph printing of nested functions

   The function graph tracer needs to look at the next event to see if
   the next event is the return of the current function entry. If it is,
   it prints a single line:

	ktime_get();

   Otherwise it prints it like a nested function:

	tick_nohz_irq_exit() {
	    ktime_get();
	    kcpustat_irq_exit();
	}

   In order to look at the next event, it must save the current event so
   that it has the information to print from it. It saves the event in
   the iterator descriptor called "ent". What it doesn't save is the
   ent_size of the event which is now used to know if the function graph
   arguments are to be printed. The peek doesn't save the size so the
   size used happens to be that of the size of the last event that was
   seen.

   Save the entry event size in the iterator descriptor so that the
   correct size is used.

 - Fix several errors with freeing data in the histogram code

   The histogram code had a lot of leaked or or incorrect accounting
   when failures happen. Correct them.

 - Fix histogram regression of .percent and .graph modifiers

   Up until 6.3 histogram values could have "percent" or "graph"
   modifiers that changed how they were printed. But a change that added
   restricting histograms values from being strings, stack traces and
   other modifiers inadvertently prevented them from using the percent
   and graph modifiers, which were legal use cases for values.

   Put back the percent and graph modifiers.

 - Fix various typos in the comments

 - Set the trace_clock before initializing a histogram with clock
   argument

   The histogram API allows the user to specific which trace clock to
   use via a "clock=" string. The histogram is set up first before the
   clock is checked. If the passed in clock is not valid, it exits
   without fully fixing up the histogram leaving it on the list and a
   use-after-free can trigger.

   Update the clock argument first and if it fails then exit gracefully
   before the histogram trigger is placed on any lists.

 - Restore :mod: trailer after parsing in ftrace_set_clr_event

   The function ftrace_set_clr_event() modifies the parse string and
   needs to put it back to what was passed in. It searches for ":mod:"
   via a strsep() but fails to put back the first ':' in the string.

   Add back the ':' in the passed in string.

 - Take trace_array reference when opening a tracer options file

   The options files are dynamically created and some tracers add their
   own options. When a tracer adds their own list of options, the
   trace_array holding them has an array to hold the list of options for
   each tracer. This array increases in size via a krealloc(), and the
   new entry gets a newly allocated array to hold the options of the new
   tracer being added.

   The element in each entry of the tracer's option array holds a
   pointer back to the trace_array, a pointer to the tracer it is
   associated to, a pointer to the flags of the option.

   The issue is that these arrays are freed when the trace_array is
   freed when its instance it represents is removed from the instances
   directory. There's a race that an open of one of these options files
   can happen when the instance is being removed.

   Add a new helper function to be called by the open function of the
   options file to iterate all existing trace_arrays under a lock and
   find the one that has the given option element in one of it's tracer
   arrays. If found, then update the associated trace_array's reference
   counter to keep it from being freed. If not found, have the open call
   return -ENODEV.

 - Disable interrupts when acquiring the lock in rb_wake_up_waiters()

   The function rb_wake_up_waiters() assumes it will be called in
   interrupt context and does not disable irqs when taking
   cpu_buffer->reader_lock, which can be called in hard interrupt
   context. The issue is in PREEMPT_RT, this function is called in
   thread context leaving this lock open to a deadlock.

   Take the lock with interrupts disabled.

 - Use rcu_assign_pointer() for tmp_ops filter hash

   The tmp_ops used in update_ftrace_direct_mod() assigns its
   filter_hash field directly, but that field is annotated as __rcu and
   sparse complains. Assign it with rcu_assign_pointer()

 - Fix use-after-free in enable_trigger_private_data_free()

   The trace_event_call is accessed through the event_trigger_data's
   trace_event_file pointer to put the trace_event_call on freeing. The
   issue is that the trace_event_file data may have been freed already
   causing a use-after-free. Add a field to the event_trigger_data that
   points directly to the trace_event_call so that it can decrement its
   reference directly without needing to go through the
   trace_event_file.

 - Fix accounting of buffer data remote headers

   trace_buffer_desc_size() and trace_remote_alloc_buffer() undercount
   the number of pages is needed for the asked for size as it doesn't
   take into account the meta data on each page. Add a helper function
   to do the calculation properly and use that in these functions.

 - Catch nr_page_va overflow in ring_buffer_desc sizing

   The number of pages per remote ring buffer is capped by
   ring_buffer_desc::nr_page_va (32 bits). A buffer_size large enough to
   overflow that field would silently allocate a descriptor smaller than
   what was asked for.

 - Do not resize the subbuf order if any per_cpu buffer is disabled

   The mmapping of ring buffers disables resizing the subbuffers, but it
   is done per-cpu whereas the subbuf size change is done for all the
   per_cpu buffers under the buffer->mutex. It could change the size of
   some while the mapping is happening on others. Have the resize of the
   subbuf order check all the per_cpu buffers under the lock to see if
   any of them is disabled before starting and causing an inconsistency
   between buffers that are being mapped.

* tag 'trace-v7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: (25 commits)
  ring-buffer: Check resize_disabled before publishing the new subbuf order
  tracing/remotes: Catch nr_page_va overflow in ring_buffer_desc sizing
  tracing/remotes: Account for ring buffer page header in size calculation
  tracing: Don't dereference trace_event_file in deferred trigger free
  ftrace: Use rcu_assign_pointer() for tmp_ops filter hash
  ring-buffer: Acquire the lock with irqsave in rb_wake_up_waiters()
  tracing: Take trace_array reference when opening a tracer options file
  tracing: Fix ring_buffer_read_page_size() kernel-doc
  tracing: Restore :mod: trailer after parsing in ftrace_set_clr_event()
  tracing: Fix memory corruption from a "STACKTRACE" histogram key
  tracing: Fix memory corruption from the histogram stacktrace modifier
  tracing: Undo the registration when enabling the histogram trigger fails
  tracing: Take the reference before publishing the named histogram trigger
  tracing: Set the trace clock before registering the histogram trigger
  tracing: Fix typo "preceeded" in comment
  tracing: Fix typo "availabe" in comment
  tracing: Let histogram values keep the percent and graph modifiers
  tracing: Keep the entry count when the histogram stats allocation fails
  tracing: Free histogram the field rejected for a bad modifier
  tracing: Free histogram the var ref when its initialization fails
  ...

6 files changed, 560 insertions, 0 deletions

diff --git a/Documentation/driver-api/mei/hdcp.rst b/Documentation/driver-api/mei/hdcp.rst
new file mode 100644
index 000000000..e85a065b1
--- /dev/null
+++ b/Documentation/driver-api/mei/hdcp.rst
@@ -0,0 +1,32 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+HDCP:
+=====
+
+ME FW as a security engine provides the capability for setting up
+HDCP2.2 protocol negotiation between the Intel graphics device and
+an HDC2.2 sink.
+
+ME FW prepares HDCP2.2 negotiation parameters, signs and encrypts them
+according the HDCP 2.2 spec. The Intel graphics sends the created blob
+to the HDCP2.2 sink.
+
+Similarly, the HDCP2.2 sink's response is transferred to ME FW
+for decryption and verification.
+
+Once all the steps of HDCP2.2 negotiation are completed,
+upon request ME FW will configure the port as authenticated and supply
+the HDCP encryption keys to Intel graphics hardware.
+
+
+mei_hdcp driver
+---------------
+.. kernel-doc:: drivers/misc/mei/hdcp/mei_hdcp.c
+    :doc: MEI_HDCP Client Driver
+
+mei_hdcp api
+------------
+
+.. kernel-doc:: drivers/misc/mei/hdcp/mei_hdcp.c
+    :functions:
+
diff --git a/Documentation/driver-api/mei/iamt.rst b/Documentation/driver-api/mei/iamt.rst
new file mode 100644
index 000000000..6ef3e6136
--- /dev/null
+++ b/Documentation/driver-api/mei/iamt.rst
@@ -0,0 +1,101 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+Intel(R) Active Management Technology (Intel AMT)
+=================================================
+
+Prominent usage of the Intel ME Interface is to communicate with Intel(R)
+Active Management Technology (Intel AMT) implemented in firmware running on
+the Intel ME.
+
+Intel AMT provides the ability to manage a host remotely out-of-band (OOB)
+even when the operating system running on the host processor has crashed or
+is in a sleep state.
+
+Some examples of Intel AMT usage are:
+   - Monitoring hardware state and platform components
+   - Remote power off/on (useful for green computing or overnight IT
+     maintenance)
+   - OS updates
+   - Storage of useful platform information such as software assets
+   - Built-in hardware KVM
+   - Selective network isolation of Ethernet and IP protocol flows based
+     on policies set by a remote management console
+   - IDE device redirection from remote management console
+
+Intel AMT (OOB) communication is based on SOAP (deprecated
+starting with Release 6.0) over HTTP/S or WS-Management protocol over
+HTTP/S that are received from a remote management console application.
+
+For more information about Intel AMT:
+https://software.intel.com/sites/manageability/AMT_Implementation_and_Reference_Guide/default.htm
+
+
+Intel AMT Applications
+----------------------
+
+    1) Intel Local Management Service (Intel LMS)
+
+       Applications running locally on the platform communicate with Intel AMT Release
+       2.0 and later releases in the same way that network applications do via SOAP
+       over HTTP (deprecated starting with Release 6.0) or with WS-Management over
+       SOAP over HTTP. This means that some Intel AMT features can be accessed from a
+       local application using the same network interface as a remote application
+       communicating with Intel AMT over the network.
+
+       When a local application sends a message addressed to the local Intel AMT host
+       name, the Intel LMS, which listens for traffic directed to the host name,
+       intercepts the message and routes it to the Intel MEI.
+       For more information:
+       https://software.intel.com/sites/manageability/AMT_Implementation_and_Reference_Guide/default.htm
+       Under "About Intel AMT" => "Local Access"
+
+       For downloading Intel LMS:
+       https://github.com/intel/lms
+
+       The Intel LMS opens a connection using the Intel MEI driver to the Intel LMS
+       firmware feature using a defined GUID and then communicates with the feature
+       using a protocol called Intel AMT Port Forwarding Protocol (Intel APF protocol).
+       The protocol is used to maintain multiple sessions with Intel AMT from a
+       single application.
+
+       See the protocol specification in the Intel AMT Software Development Kit (SDK)
+       https://software.intel.com/sites/manageability/AMT_Implementation_and_Reference_Guide/default.htm
+       Under "SDK Resources" => "Intel(R) vPro(TM) Gateway (MPS)"
+       => "Information for Intel(R) vPro(TM) Gateway Developers"
+       => "Description of the Intel AMT Port Forwarding (APF) Protocol"
+
+    2) Intel AMT Remote configuration using a Local Agent
+
+       A Local Agent enables IT personnel to configure Intel AMT out-of-the-box
+       without requiring installing additional data to enable setup. The remote
+       configuration process may involve an ISV-developed remote configuration
+       agent that runs on the host.
+       For more information:
+       https://software.intel.com/sites/manageability/AMT_Implementation_and_Reference_Guide/default.htm
+       Under "Setup and Configuration of Intel AMT" =>
+       "SDK Tools Supporting Setup and Configuration" =>
+       "Using the Local Agent Sample"
+
+Intel AMT OS Health Watchdog
+----------------------------
+
+The Intel AMT Watchdog is an OS Health (Hang/Crash) watchdog.
+Whenever the OS hangs or crashes, Intel AMT will send an event
+to any subscriber to this event. This mechanism means that
+IT knows when a platform crashes even when there is a hard failure on the host.
+
+The Intel AMT Watchdog is composed of two parts:
+    1) Firmware feature - receives the heartbeats
+       and sends an event when the heartbeats stop.
+    2) Intel MEI iAMT watchdog driver - connects to the watchdog feature,
+       configures the watchdog and sends the heartbeats.
+
+The Intel iAMT watchdog MEI driver uses the kernel watchdog API to configure
+the Intel AMT Watchdog and to send heartbeats to it. The default timeout of the
+watchdog is 120 seconds.
+
+If the Intel AMT is not enabled in the firmware then the watchdog client won't enumerate
+on the me client bus and watchdog devices won't be exposed.
+
+---
+linux-mei@linux.intel.com
diff --git a/Documentation/driver-api/mei/index.rst b/Documentation/driver-api/mei/index.rst
new file mode 100644
index 000000000..eae6f18f1
--- /dev/null
+++ b/Documentation/driver-api/mei/index.rst
@@ -0,0 +1,18 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+.. include:: <isonum.txt>
+
+===================================================
+Intel(R) Management Engine Interface (Intel(R) MEI)
+===================================================
+
+**Copyright** |copy| 2019 Intel Corporation
+
+
+.. toctree::
+   :caption: Table of Contents
+   :maxdepth: 3
+
+   mei
+   mei-client-bus
+   iamt
diff --git a/Documentation/driver-api/mei/mei-client-bus.rst b/Documentation/driver-api/mei/mei-client-bus.rst
new file mode 100644
index 000000000..f242b3f8d
--- /dev/null
+++ b/Documentation/driver-api/mei/mei-client-bus.rst
@@ -0,0 +1,168 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+==============================================
+Intel(R) Management Engine (ME) Client bus API
+==============================================
+
+
+Rationale
+=========
+
+The MEI character device is useful for dedicated applications to send and receive
+data to the many FW appliance found in Intel's ME from the user space.
+However, for some of the ME functionalities it makes sense to leverage existing software
+stack and expose them through existing kernel subsystems.
+
+In order to plug seamlessly into the kernel device driver model we add kernel virtual
+bus abstraction on top of the MEI driver. This allows implementing Linux kernel drivers
+for the various MEI features as a stand alone entities found in their respective subsystem.
+Existing device drivers can even potentially be re-used by adding an MEI CL bus layer to
+the existing code.
+
+
+MEI CL bus API
+==============
+
+A driver implementation for an MEI Client is very similar to any other existing bus
+based device drivers. The driver registers itself as an MEI CL bus driver through
+the ``struct mei_cl_driver`` structure defined in :file:`include/linux/mei_cl_bus.c`
+
+.. code-block:: C
+
+        struct mei_cl_driver {
+                struct device_driver driver;
+                const char *name;
+
+                const struct mei_cl_device_id *id_table;
+
+                int (*probe)(struct mei_cl_device *dev, const struct mei_cl_id *id);
+                int (*remove)(struct mei_cl_device *dev);
+        };
+
+
+
+The mei_cl_device_id structure defined in :file:`include/linux/mod_devicetable.h` allows a
+driver to bind itself against a device name.
+
+.. code-block:: C
+
+        struct mei_cl_device_id {
+                char name[MEI_CL_NAME_SIZE];
+                uuid_le uuid;
+                __u8    version;
+                kernel_ulong_t driver_info;
+        };
+
+To actually register a driver on the ME Client bus one must call the :c:func:`mei_cl_add_driver`
+API. This is typically called at module initialization time.
+
+Once the driver is registered and bound to the device, a driver will typically
+try to do some I/O on this bus and this should be done through the :c:func:`mei_cl_send`
+and :c:func:`mei_cl_recv` functions. More detailed information is in :ref:`api` section.
+
+In order for a driver to be notified about pending traffic or event, the driver
+should register a callback via :c:func:`mei_cl_devev_register_rx_cb` and
+:c:func:`mei_cldev_register_notify_cb` function respectively.
+
+.. _api:
+
+API:
+----
+.. kernel-doc:: drivers/misc/mei/bus.c
+    :export: drivers/misc/mei/bus.c
+
+
+
+Example
+=======
+
+As a theoretical example let's pretend the ME comes with a "contact" NFC IP.
+The driver init and exit routines for this device would look like:
+
+.. code-block:: C
+
+        #define CONTACT_DRIVER_NAME "contact"
+
+        static struct mei_cl_device_id contact_mei_cl_tbl[] = {
+                { CONTACT_DRIVER_NAME, },
+
+                /* required last entry */
+                { }
+        };
+        MODULE_DEVICE_TABLE(mei_cl, contact_mei_cl_tbl);
+
+        static struct mei_cl_driver contact_driver = {
+                .id_table = contact_mei_tbl,
+                .name = CONTACT_DRIVER_NAME,
+
+                .probe = contact_probe,
+                .remove = contact_remove,
+        };
+
+        static int contact_init(void)
+        {
+                int r;
+
+                r = mei_cl_driver_register(&contact_driver);
+                if (r) {
+                        pr_err(CONTACT_DRIVER_NAME ": driver registration failed\n");
+                        return r;
+                }
+
+                return 0;
+        }
+
+        static void __exit contact_exit(void)
+        {
+                mei_cl_driver_unregister(&contact_driver);
+        }
+
+        module_init(contact_init);
+        module_exit(contact_exit);
+
+And the driver's simplified probe routine would look like that:
+
+.. code-block:: C
+
+        int contact_probe(struct mei_cl_device *dev, struct mei_cl_device_id *id)
+        {
+                [...]
+                mei_cldev_enable(dev);
+
+                mei_cldev_register_rx_cb(dev, contact_rx_cb);
+
+                return 0;
+        }
+
+In the probe routine the driver first enable the MEI device and then registers
+an rx handler which is as close as it can get to registering a threaded IRQ handler.
+The handler implementation will typically call :c:func:`mei_cldev_recv` and then
+process received data.
+
+.. code-block:: C
+
+        #define MAX_PAYLOAD 128
+        #define HDR_SIZE 4
+        static void conntact_rx_cb(struct mei_cl_device *cldev)
+        {
+                struct contact *c = mei_cldev_get_drvdata(cldev);
+                unsigned char payload[MAX_PAYLOAD];
+                ssize_t payload_sz;
+
+                payload_sz = mei_cldev_recv(cldev, payload,  MAX_PAYLOAD)
+                if (reply_size < HDR_SIZE) {
+                        return;
+                }
+
+                c->process_rx(payload);
+
+        }
+
+MEI Client Bus Drivers
+======================
+
+.. toctree::
+   :maxdepth: 2
+
+   hdcp
+   nfc
diff --git a/Documentation/driver-api/mei/mei.rst b/Documentation/driver-api/mei/mei.rst
new file mode 100644
index 000000000..4f2ced4cc
--- /dev/null
+++ b/Documentation/driver-api/mei/mei.rst
@@ -0,0 +1,213 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+Introduction
+============
+
+The Intel Management Engine (Intel ME) is an isolated and protected computing
+resource (Co-processor) residing inside certain Intel chipsets. The Intel ME
+provides support for computer/IT management and security features.
+The actual feature set depends on the Intel chipset SKU.
+
+The Intel Management Engine Interface (Intel MEI, previously known as HECI)
+is the interface between the Host and Intel ME. This interface is exposed
+to the host as a PCI device, actually multiple PCI devices might be exposed.
+The Intel MEI Driver is in charge of the communication channel between
+a host application and the Intel ME features.
+
+Each Intel ME feature, or Intel ME Client is addressed by a unique GUID and
+each client has its own protocol. The protocol is message-based with a
+header and payload up to maximal number of bytes advertised by the client,
+upon connection.
+
+Intel MEI Driver
+================
+
+The driver exposes a character device with device nodes /dev/meiX.
+
+An application maintains communication with an Intel ME feature while
+/dev/meiX is open. The binding to a specific feature is performed by calling
+:c:macro:`MEI_CONNECT_CLIENT_IOCTL`, which passes the desired GUID.
+The number of instances of an Intel ME feature that can be opened
+at the same time depends on the Intel ME feature, but most of the
+features allow only a single instance.
+
+The driver is transparent to data that are passed between firmware feature
+and host application.
+
+Because some of the Intel ME features can change the system
+configuration, the driver by default allows only a privileged
+user to access it.
+
+The session is terminated calling :c:expr:`close(fd)`.
+
+A code snippet for an application communicating with Intel AMTHI client:
+
+In order to support virtualization or sandboxing a trusted supervisor
+can use :c:macro:`MEI_CONNECT_CLIENT_IOCTL_VTAG` to create
+virtual channels with an Intel ME feature. Not all features support
+virtual channels such client with answer EOPNOTSUPP.
+
+.. code-block:: C
+
+	struct mei_connect_client_data data;
+	fd = open(MEI_DEVICE);
+
+	data.d.in_client_uuid = AMTHI_GUID;
+
+	ioctl(fd, IOCTL_MEI_CONNECT_CLIENT, &data);
+
+	printf("Ver=%d, MaxLen=%ld\n",
+	       data.d.in_client_uuid.protocol_version,
+	       data.d.in_client_uuid.max_msg_length);
+
+	[...]
+
+	write(fd, amthi_req_data, amthi_req_data_len);
+
+	[...]
+
+	read(fd, &amthi_res_data, amthi_res_data_len);
+
+	[...]
+	close(fd);
+
+
+User space API
+
+IOCTLs:
+=======
+
+The Intel MEI Driver supports the following IOCTL commands:
+
+IOCTL_MEI_CONNECT_CLIENT
+-------------------------
+Connect to firmware Feature/Client.
+
+.. code-block:: none
+
+	Usage:
+
+        struct mei_connect_client_data client_data;
+
+        ioctl(fd, IOCTL_MEI_CONNECT_CLIENT, &client_data);
+
+	Inputs:
+
+        struct mei_connect_client_data - contain the following
+	Input field:
+
+		in_client_uuid -	GUID of the FW Feature that needs
+					to connect to.
+         Outputs:
+		out_client_properties - Client Properties: MTU and Protocol Version.
+
+         Error returns:
+
+                ENOTTY  No such client (i.e. wrong GUID) or connection is not allowed.
+		EINVAL	Wrong IOCTL Number
+		ENODEV	Device or Connection is not initialized or ready.
+		ENOMEM	Unable to allocate memory to client internal data.
+		EFAULT	Fatal Error (e.g. Unable to access user input data)
+		EBUSY	Connection Already Open
+
+:Note:
+        max_msg_length (MTU) in client properties describes the maximum
+        data that can be sent or received. (e.g. if MTU=2K, can send
+        requests up to bytes 2k and received responses up to 2k bytes).
+
+IOCTL_MEI_CONNECT_CLIENT_VTAG:
+------------------------------
+
+.. code-block:: none
+
+        Usage:
+
+        struct mei_connect_client_data_vtag client_data_vtag;
+
+        ioctl(fd, IOCTL_MEI_CONNECT_CLIENT_VTAG, &client_data_vtag);
+
+        Inputs:
+
+        struct mei_connect_client_data_vtag - contain the following
+        Input field:
+
+                in_client_uuid -  GUID of the FW Feature that needs
+                                  to connect to.
+                vtag - virtual tag [1, 255]
+
+         Outputs:
+                out_client_properties - Client Properties: MTU and Protocol Version.
+
+         Error returns:
+
+                ENOTTY No such client (i.e. wrong GUID) or connection is not allowed.
+                EINVAL Wrong IOCTL Number or tag == 0
+                ENODEV Device or Connection is not initialized or ready.
+                ENOMEM Unable to allocate memory to client internal data.
+                EFAULT Fatal Error (e.g. Unable to access user input data)
+                EBUSY  Connection Already Open
+                EOPNOTSUPP Vtag is not supported
+
+IOCTL_MEI_NOTIFY_SET
+---------------------
+Enable or disable event notifications.
+
+
+.. code-block:: none
+
+	Usage:
+
+		uint32_t enable;
+
+		ioctl(fd, IOCTL_MEI_NOTIFY_SET, &enable);
+
+
+		uint32_t enable = 1;
+		or
+		uint32_t enable[disable] = 0;
+
+	Error returns:
+
+
+		EINVAL	Wrong IOCTL Number
+		ENODEV	Device  is not initialized or the client not connected
+		ENOMEM	Unable to allocate memory to client internal data.
+		EFAULT	Fatal Error (e.g. Unable to access user input data)
+		EOPNOTSUPP if the device doesn't support the feature
+
+:Note:
+	The client must be connected in order to enable notification events
+
+
+IOCTL_MEI_NOTIFY_GET
+--------------------
+Retrieve event
+
+.. code-block:: none
+
+	Usage:
+		uint32_t event;
+		ioctl(fd, IOCTL_MEI_NOTIFY_GET, &event);
+
+	Outputs:
+		1 - if an event is pending
+		0 - if there is no even pending
+
+	Error returns:
+		EINVAL	Wrong IOCTL Number
+		ENODEV	Device is not initialized or the client not connected
+		ENOMEM	Unable to allocate memory to client internal data.
+		EFAULT	Fatal Error (e.g. Unable to access user input data)
+		EOPNOTSUPP if the device doesn't support the feature
+
+:Note:
+	The client must be connected and event notification has to be enabled
+	in order to receive an event
+
+
+
+Supported Chipsets
+==================
+82X38/X48 Express and newer
+
+linux-mei@linux.intel.com
diff --git a/Documentation/driver-api/mei/nfc.rst b/Documentation/driver-api/mei/nfc.rst
new file mode 100644
index 000000000..8fe8664c2
--- /dev/null
+++ b/Documentation/driver-api/mei/nfc.rst
@@ -0,0 +1,28 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+MEI NFC
+-------
+
+Some Intel 8 and 9 Series chipsets support NFC devices connected behind
+the Intel Management Engine controller.
+MEI client bus exposes the NFC chips as NFC phy devices and enables
+binding with Microread and NXP PN544 NFC device driver from the Linux NFC
+subsystem.
+
+.. kernel-render:: DOT
+   :alt: MEI NFC digraph
+   :caption: **MEI NFC** Stack
+
+   digraph NFC {
+    cl_nfc -> me_cl_nfc;
+    "drivers/nfc/mei_phy" -> cl_nfc [lhead=bus];
+    "drivers/nfc/microread/mei" -> cl_nfc;
+    "drivers/nfc/microread/mei" -> "drivers/nfc/mei_phy";
+    "drivers/nfc/pn544/mei" -> cl_nfc;
+    "drivers/nfc/pn544/mei" -> "drivers/nfc/mei_phy";
+    "net/nfc" -> "drivers/nfc/microread/mei";
+    "net/nfc" -> "drivers/nfc/pn544/mei";
+    "neard" -> "net/nfc";
+    cl_nfc [label="mei/bus(nfc)"];
+    me_cl_nfc [label="me fw (nfc)"];
+   }