Merge branch 'core/urgent' into x86/urgent, to pick up objtool fix

Signed-off-by: Ingo Molnar <mingo@kernel.org>

14 files changed, 652 insertions, 0 deletions

diff --git a/Documentation/media/uapi/mediactl/media-controller.rst b/Documentation/media/uapi/mediactl/media-controller.rst
index 0eea4f9a07d5..66aff38cd499 100644
--- a/Documentation/media/uapi/mediactl/media-controller.rst
+++ b/Documentation/media/uapi/mediactl/media-controller.rst
@@ -21,6 +21,7 @@ Part IV - Media Controller API
     media-controller-intro
     media-controller-model
     media-types
+    request-api
     media-funcs
     media-header
 
diff --git a/Documentation/media/uapi/mediactl/media-funcs.rst b/Documentation/media/uapi/mediactl/media-funcs.rst
index 076856501cdb..260f9dcadcde 100644
--- a/Documentation/media/uapi/mediactl/media-funcs.rst
+++ b/Documentation/media/uapi/mediactl/media-funcs.rst
@@ -16,3 +16,9 @@ Function Reference
     media-ioc-enum-entities
     media-ioc-enum-links
     media-ioc-setup-link
+    media-ioc-request-alloc
+    request-func-close
+    request-func-ioctl
+    request-func-poll
+    media-request-ioc-queue
+    media-request-ioc-reinit
diff --git a/Documentation/media/uapi/mediactl/media-ioc-device-info.rst b/Documentation/media/uapi/mediactl/media-ioc-device-info.rst
index 649cb3d9e058..c6f224e404b7 100644
--- a/Documentation/media/uapi/mediactl/media-ioc-device-info.rst
+++ b/Documentation/media/uapi/mediactl/media-ioc-device-info.rst
@@ -26,6 +26,7 @@ Arguments
     File descriptor returned by :ref:`open() <media-func-open>`.
 
 ``argp``
+    Pointer to struct :c:type:`media_device_info`.
 
 
 Description
diff --git a/Documentation/media/uapi/mediactl/media-ioc-enum-entities.rst b/Documentation/media/uapi/mediactl/media-ioc-enum-entities.rst
index fc2e39c070c9..02738640e34e 100644
--- a/Documentation/media/uapi/mediactl/media-ioc-enum-entities.rst
+++ b/Documentation/media/uapi/mediactl/media-ioc-enum-entities.rst
@@ -26,6 +26,7 @@ Arguments
     File descriptor returned by :ref:`open() <media-func-open>`.
 
 ``argp``
+    Pointer to struct :c:type:`media_entity_desc`.
 
 
 Description
diff --git a/Documentation/media/uapi/mediactl/media-ioc-enum-links.rst b/Documentation/media/uapi/mediactl/media-ioc-enum-links.rst
index f158c134e9b0..b89aaae373df 100644
--- a/Documentation/media/uapi/mediactl/media-ioc-enum-links.rst
+++ b/Documentation/media/uapi/mediactl/media-ioc-enum-links.rst
@@ -26,6 +26,7 @@ Arguments
     File descriptor returned by :ref:`open() <media-func-open>`.
 
 ``argp``
+    Pointer to struct :c:type:`media_links_enum`.
 
 
 Description
diff --git a/Documentation/media/uapi/mediactl/media-ioc-g-topology.rst b/Documentation/media/uapi/mediactl/media-ioc-g-topology.rst
index bac128c7eda9..4e1c59238371 100644
--- a/Documentation/media/uapi/mediactl/media-ioc-g-topology.rst
+++ b/Documentation/media/uapi/mediactl/media-ioc-g-topology.rst
@@ -26,6 +26,7 @@ Arguments
     File descriptor returned by :ref:`open() <media-func-open>`.
 
 ``argp``
+    Pointer to struct :c:type:`media_v2_topology`.
 
 
 Description
diff --git a/Documentation/media/uapi/mediactl/media-ioc-request-alloc.rst b/Documentation/media/uapi/mediactl/media-ioc-request-alloc.rst
new file mode 100644
index 000000000000..0f8b31874002
--- /dev/null
+++ b/Documentation/media/uapi/mediactl/media-ioc-request-alloc.rst
@@ -0,0 +1,66 @@
+.. SPDX-License-Identifier: GPL-2.0 OR GFDL-1.1-or-later WITH no-invariant-sections
+
+.. _media_ioc_request_alloc:
+
+*****************************
+ioctl MEDIA_IOC_REQUEST_ALLOC
+*****************************
+
+Name
+====
+
+MEDIA_IOC_REQUEST_ALLOC - Allocate a request
+
+
+Synopsis
+========
+
+.. c:function:: int ioctl( int fd, MEDIA_IOC_REQUEST_ALLOC, int *argp )
+    :name: MEDIA_IOC_REQUEST_ALLOC
+
+
+Arguments
+=========
+
+``fd``
+    File descriptor returned by :ref:`open() <media-func-open>`.
+
+``argp``
+    Pointer to an integer.
+
+
+Description
+===========
+
+If the media device supports :ref:`requests <media-request-api>`, then
+this ioctl can be used to allocate a request. If it is not supported, then
+``errno`` is set to ``ENOTTY``. A request is accessed through a file descriptor
+that is returned in ``*argp``.
+
+If the request was successfully allocated, then the request file descriptor
+can be passed to the :ref:`VIDIOC_QBUF <VIDIOC_QBUF>`,
+:ref:`VIDIOC_G_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>`,
+:ref:`VIDIOC_S_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` and
+:ref:`VIDIOC_TRY_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` ioctls.
+
+In addition, the request can be queued by calling
+:ref:`MEDIA_REQUEST_IOC_QUEUE` and re-initialized by calling
+:ref:`MEDIA_REQUEST_IOC_REINIT`.
+
+Finally, the file descriptor can be :ref:`polled <request-func-poll>` to wait
+for the request to complete.
+
+The request will remain allocated until all the file descriptors associated
+with it are closed by :ref:`close() <request-func-close>` and the driver no
+longer uses the request internally. See also
+:ref:`here <media-request-life-time>` for more information.
+
+Return Value
+============
+
+On success 0 is returned, on error -1 and the ``errno`` variable is set
+appropriately. The generic error codes are described at the
+:ref:`Generic Error Codes <gen-errors>` chapter.
+
+ENOTTY
+    The driver has no support for requests.
diff --git a/Documentation/media/uapi/mediactl/media-ioc-setup-link.rst b/Documentation/media/uapi/mediactl/media-ioc-setup-link.rst
index ae5194940100..e345e7dc9ad7 100644
--- a/Documentation/media/uapi/mediactl/media-ioc-setup-link.rst
+++ b/Documentation/media/uapi/mediactl/media-ioc-setup-link.rst
@@ -26,6 +26,7 @@ Arguments
     File descriptor returned by :ref:`open() <media-func-open>`.
 
 ``argp``
+    Pointer to struct :c:type:`media_link_desc`.
 
 
 Description
diff --git a/Documentation/media/uapi/mediactl/media-request-ioc-queue.rst b/Documentation/media/uapi/mediactl/media-request-ioc-queue.rst
new file mode 100644
index 000000000000..6dd2d7fea714
--- /dev/null
+++ b/Documentation/media/uapi/mediactl/media-request-ioc-queue.rst
@@ -0,0 +1,78 @@
+.. SPDX-License-Identifier: GPL-2.0 OR GFDL-1.1-or-later WITH no-invariant-sections
+
+.. _media_request_ioc_queue:
+
+*****************************
+ioctl MEDIA_REQUEST_IOC_QUEUE
+*****************************
+
+Name
+====
+
+MEDIA_REQUEST_IOC_QUEUE - Queue a request
+
+
+Synopsis
+========
+
+.. c:function:: int ioctl( int request_fd, MEDIA_REQUEST_IOC_QUEUE )
+    :name: MEDIA_REQUEST_IOC_QUEUE
+
+
+Arguments
+=========
+
+``request_fd``
+    File descriptor returned by :ref:`MEDIA_IOC_REQUEST_ALLOC`.
+
+
+Description
+===========
+
+If the media device supports :ref:`requests <media-request-api>`, then
+this request ioctl can be used to queue a previously allocated request.
+
+If the request was successfully queued, then the file descriptor can be
+:ref:`polled <request-func-poll>` to wait for the request to complete.
+
+If the request was already queued before, then ``EBUSY`` is returned.
+Other errors can be returned if the contents of the request contained
+invalid or inconsistent data, see the next section for a list of
+common error codes. On error both the request and driver state are unchanged.
+
+Once a request is queued, then the driver is required to gracefully handle
+errors that occur when the request is applied to the hardware. The
+exception is the ``EIO`` error which signals a fatal error that requires
+the application to stop streaming to reset the hardware state.
+
+It is not allowed to mix queuing requests with queuing buffers directly
+(without a request). ``EBUSY`` will be returned if the first buffer was
+queued directly and you next try to queue a request, or vice versa.
+
+A request must contain at least one buffer, otherwise this ioctl will
+return an ``ENOENT`` error.
+
+Return Value
+============
+
+On success 0 is returned, on error -1 and the ``errno`` variable is set
+appropriately. The generic error codes are described at the
+:ref:`Generic Error Codes <gen-errors>` chapter.
+
+EBUSY
+    The request was already queued or the application queued the first
+    buffer directly, but later attempted to use a request. It is not permitted
+    to mix the two APIs.
+ENOENT
+    The request did not contain any buffers. All requests are required
+    to have at least one buffer. This can also be returned if some required
+    configuration is missing in the request.
+ENOMEM
+    Out of memory when allocating internal data structures for this
+    request.
+EINVAL
+    The request has invalid data.
+EIO
+    The hardware is in a bad state. To recover, the application needs to
+    stop streaming to reset the hardware state and then try to restart
+    streaming.
diff --git a/Documentation/media/uapi/mediactl/media-request-ioc-reinit.rst b/Documentation/media/uapi/mediactl/media-request-ioc-reinit.rst
new file mode 100644
index 000000000000..febe888494c8
--- /dev/null
+++ b/Documentation/media/uapi/mediactl/media-request-ioc-reinit.rst
@@ -0,0 +1,51 @@
+.. SPDX-License-Identifier: GPL-2.0 OR GFDL-1.1-or-later WITH no-invariant-sections
+
+.. _media_request_ioc_reinit:
+
+******************************
+ioctl MEDIA_REQUEST_IOC_REINIT
+******************************
+
+Name
+====
+
+MEDIA_REQUEST_IOC_REINIT - Re-initialize a request
+
+
+Synopsis
+========
+
+.. c:function:: int ioctl( int request_fd, MEDIA_REQUEST_IOC_REINIT )
+    :name: MEDIA_REQUEST_IOC_REINIT
+
+
+Arguments
+=========
+
+``request_fd``
+    File descriptor returned by :ref:`MEDIA_IOC_REQUEST_ALLOC`.
+
+Description
+===========
+
+If the media device supports :ref:`requests <media-request-api>`, then
+this request ioctl can be used to re-initialize a previously allocated
+request.
+
+Re-initializing a request will clear any existing data from the request.
+This avoids having to :ref:`close() <request-func-close>` a completed
+request and allocate a new request. Instead the completed request can just
+be re-initialized and it is ready to be used again.
+
+A request can only be re-initialized if it either has not been queued
+yet, or if it was queued and completed. Otherwise it will set ``errno``
+to ``EBUSY``. No other error codes can be returned.
+
+Return Value
+============
+
+On success 0 is returned, on error -1 and the ``errno`` variable is set
+appropriately.
+
+EBUSY
+    The request is queued but not yet completed.
diff --git a/Documentation/media/uapi/mediactl/request-api.rst b/Documentation/media/uapi/mediactl/request-api.rst
new file mode 100644
index 000000000000..5f4a23029c48
--- /dev/null
+++ b/Documentation/media/uapi/mediactl/request-api.rst
@@ -0,0 +1,252 @@
+.. SPDX-License-Identifier: GPL-2.0 OR GFDL-1.1-or-later WITH no-invariant-sections
+
+.. _media-request-api:
+
+Request API
+===========
+
+The Request API has been designed to allow V4L2 to deal with requirements of
+modern devices (stateless codecs, complex camera pipelines, ...) and APIs
+(Android Codec v2). One such requirement is the ability for devices belonging to
+the same pipeline to reconfigure and collaborate closely on a per-frame basis.
+Another is support of stateless codecs, which require controls to be applied
+to specific frames (aka 'per-frame controls') in order to be used efficiently.
+
+While the initial use-case was V4L2, it can be extended to other subsystems
+as well, as long as they use the media controller.
+
+Supporting these features without the Request API is not always possible and if
+it is, it is terribly inefficient: user-space would have to flush all activity
+on the media pipeline, reconfigure it for the next frame, queue the buffers to
+be processed with that configuration, and wait until they are all available for
+dequeuing before considering the next frame. This defeats the purpose of having
+buffer queues since in practice only one buffer would be queued at a time.
+
+The Request API allows a specific configuration of the pipeline (media
+controller topology + configuration for each media entity) to be associated with
+specific buffers. This allows user-space to schedule several tasks ("requests")
+with different configurations in advance, knowing that the configuration will be
+applied when needed to get the expected result. Configuration values at the time
+of request completion are also available for reading.
+
+Usage
+=====
+
+The Request API extends the Media Controller API and cooperates with
+subsystem-specific APIs to support request usage. At the Media Controller
+level, requests are allocated from the supporting Media Controller device
+node. Their life cycle is then managed through the request file descriptors in
+an opaque way. Configuration data, buffer handles and processing results
+stored in requests are accessed through subsystem-specific APIs extended for
+request support, such as V4L2 APIs that take an explicit ``request_fd``
+parameter.
+
+Request Allocation
+------------------
+
+User-space allocates requests using :ref:`MEDIA_IOC_REQUEST_ALLOC`
+for the media device node. This returns a file descriptor representing the
+request. Typically, several such requests will be allocated.
+
+Request Preparation
+-------------------
+
+Standard V4L2 ioctls can then receive a request file descriptor to express the
+fact that the ioctl is part of said request, and is not to be applied
+immediately. See :ref:`MEDIA_IOC_REQUEST_ALLOC` for a list of ioctls that
+support this. Configurations set with a ``request_fd`` parameter are stored
+instead of being immediately applied, and buffers queued to a request do not
+enter the regular buffer queue until the request itself is queued.
+
+Request Submission
+------------------
+
+Once the configuration and buffers of the request are specified, it can be
+queued by calling :ref:`MEDIA_REQUEST_IOC_QUEUE` on the request file descriptor.
+A request must contain at least one buffer, otherwise ``ENOENT`` is returned.
+A queued request cannot be modified anymore.
+
+.. caution::
+   For :ref:`memory-to-memory devices <codec>` you can use requests only for
+   output buffers, not for capture buffers. Attempting to add a capture buffer
+   to a request will result in an ``EACCES`` error.
+
+If the request contains configurations for multiple entities, individual drivers
+may synchronize so the requested pipeline's topology is applied before the
+buffers are processed. Media controller drivers do a best effort implementation
+since perfect atomicity may not be possible due to hardware limitations.
+
+.. caution::
+
+   It is not allowed to mix queuing requests with directly queuing buffers:
+   whichever method is used first locks this in place until
+   :ref:`VIDIOC_STREAMOFF <VIDIOC_STREAMON>` is called or the device is
+   :ref:`closed <func-close>`. Attempts to directly queue a buffer when earlier
+   a buffer was queued via a request or vice versa will result in an ``EBUSY``
+   error.
+
+Controls can still be set without a request and are applied immediately,
+regardless of whether a request is in use or not.
+
+.. caution::
+
+   Setting the same control through a request and also directly can lead to
+   undefined behavior!
+
+User-space can :ref:`poll() <request-func-poll>` a request file descriptor in
+order to wait until the request completes. A request is considered complete
+once all its associated buffers are available for dequeuing and all the
+associated controls have been updated with the values at the time of completion.
+Note that user-space does not need to wait for the request to complete to
+dequeue its buffers: buffers that are available halfway through a request can
+be dequeued independently of the request's state.
+
+A completed request contains the state of the device after the request was
+executed. User-space can query that state by calling
+:ref:`ioctl VIDIOC_G_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` with the request file
+descriptor. Calling :ref:`ioctl VIDIOC_G_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` for a
+request that has been queued but not yet completed will return ``EBUSY``
+since the control values might be changed at any time by the driver while the
+request is in flight.
+
+.. _media-request-life-time:
+
+Recycling and Destruction
+-------------------------
+
+Finally, a completed request can either be discarded or be reused. Calling
+:ref:`close() <request-func-close>` on a request file descriptor will make
+that file descriptor unusable and the request will be freed once it is no
+longer in use by the kernel. That is, if the request is queued and then the
+file descriptor is closed, then it won't be freed until the driver completed
+the request.
+
+The :ref:`MEDIA_REQUEST_IOC_REINIT` will clear a request's state and make it
+available again. No state is retained by this operation: the request is as
+if it had just been allocated.
+
+Example for a Codec Device
+--------------------------
+
+For use-cases such as :ref:`codecs <codec>`, the request API can be used
+to associate specific controls to
+be applied by the driver for the OUTPUT buffer, allowing user-space
+to queue many such buffers in advance. It can also take advantage of requests'
+ability to capture the state of controls when the request completes to read back
+information that may be subject to change.
+
+Put into code, after obtaining a request, user-space can assign controls and one
+OUTPUT buffer to it:
+
+.. code-block:: c
+
+	struct v4l2_buffer buf;
+	struct v4l2_ext_controls ctrls;
+	int req_fd;
+	...
+	if (ioctl(media_fd, MEDIA_IOC_REQUEST_ALLOC, &req_fd))
+		return errno;
+	...
+	ctrls.which = V4L2_CTRL_WHICH_REQUEST_VAL;
+	ctrls.request_fd = req_fd;
+	if (ioctl(codec_fd, VIDIOC_S_EXT_CTRLS, &ctrls))
+		return errno;
+	...
+	buf.type = V4L2_BUF_TYPE_VIDEO_OUTPUT;
+	buf.flags |= V4L2_BUF_FLAG_REQUEST_FD;
+	buf.request_fd = req_fd;
+	if (ioctl(codec_fd, VIDIOC_QBUF, &buf))
+		return errno;
+
+Note that it is not allowed to use the Request API for CAPTURE buffers
+since there are no per-frame settings to report there.
+
+Once the request is fully prepared, it can be queued to the driver:
+
+.. code-block:: c
+
+	if (ioctl(req_fd, MEDIA_REQUEST_IOC_QUEUE))
+		return errno;
+
+User-space can then either wait for the request to complete by calling poll() on
+its file descriptor, or start dequeuing CAPTURE buffers. Most likely, it will
+want to get CAPTURE buffers as soon as possible and this can be done using a
+regular :ref:`VIDIOC_DQBUF <VIDIOC_QBUF>`:
+
+.. code-block:: c
+
+	struct v4l2_buffer buf;
+
+	memset(&buf, 0, sizeof(buf));
+	buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
+	if (ioctl(codec_fd, VIDIOC_DQBUF, &buf))
+		return errno;
+
+Note that this example assumes for simplicity that for every OUTPUT buffer
+there will be one CAPTURE buffer, but this does not have to be the case.
+
+We can then, after ensuring that the request is completed via polling the
+request file descriptor, query control values at the time of its completion via
+a call to :ref:`VIDIOC_G_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>`.
+This is particularly useful for volatile controls for which we want to
+query values as soon as the capture buffer is produced.
+
+.. code-block:: c
+
+	struct pollfd pfd = { .events = POLLPRI, .fd = req_fd };
+	poll(&pfd, 1, -1);
+	...
+	ctrls.which = V4L2_CTRL_WHICH_REQUEST_VAL;
+	ctrls.request_fd = req_fd;
+	if (ioctl(codec_fd, VIDIOC_G_EXT_CTRLS, &ctrls))
+		return errno;
+
+Once we don't need the request anymore, we can either recycle it for reuse with
+:ref:`MEDIA_REQUEST_IOC_REINIT`...
+
+.. code-block:: c
+
+	if (ioctl(req_fd, MEDIA_REQUEST_IOC_REINIT))
+		return errno;
+
+... or close its file descriptor to completely dispose of it.
+
+.. code-block:: c
+
+	close(req_fd);
+
+Example for a Simple Capture Device
+-----------------------------------
+
+With a simple capture device, requests can be used to specify controls to apply
+for a given CAPTURE buffer.
+
+.. code-block:: c
+
+	struct v4l2_buffer buf;
+	struct v4l2_ext_controls ctrls;
+	int req_fd;
+	...
+	if (ioctl(media_fd, MEDIA_IOC_REQUEST_ALLOC, &req_fd))
+		return errno;
+	...
+	ctrls.which = V4L2_CTRL_WHICH_REQUEST_VAL;
+	ctrls.request_fd = req_fd;
+	if (ioctl(camera_fd, VIDIOC_S_EXT_CTRLS, &ctrls))
+		return errno;
+	...
+	buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
+	buf.flags |= V4L2_BUF_FLAG_REQUEST_FD;
+	buf.request_fd = req_fd;
+	if (ioctl(camera_fd, VIDIOC_QBUF, &buf))
+		return errno;
+
+Once the request is fully prepared, it can be queued to the driver:
+
+.. code-block:: c
+
+	if (ioctl(req_fd, MEDIA_REQUEST_IOC_QUEUE))
+		return errno;
+
+User-space can then dequeue buffers, wait for the request completion, query
+controls and recycle the request as in the M2M example above.
diff --git a/Documentation/media/uapi/mediactl/request-func-close.rst b/Documentation/media/uapi/mediactl/request-func-close.rst
new file mode 100644
index 000000000000..098d7f2b9548
--- /dev/null
+++ b/Documentation/media/uapi/mediactl/request-func-close.rst
@@ -0,0 +1,49 @@
+.. SPDX-License-Identifier: GPL-2.0 OR GFDL-1.1-or-later WITH no-invariant-sections
+
+.. _request-func-close:
+
+***************
+request close()
+***************
+
+Name
+====
+
+request-close - Close a request file descriptor
+
+
+Synopsis
+========
+
+.. code-block:: c
+
+    #include <unistd.h>
+
+
+.. c:function:: int close( int fd )
+    :name: req-close
+
+Arguments
+=========
+
+``fd``
+    File descriptor returned by :ref:`MEDIA_IOC_REQUEST_ALLOC`.
+
+
+Description
+===========
+
+Closes the request file descriptor. Resources associated with the request
+are freed once all file descriptors associated with the request are closed
+and the driver has completed the request.
+See :ref:`here <media-request-life-time>` for more information.
+
+
+Return Value
+============
+
+:ref:`close() <request-func-close>` returns 0 on success. On error, -1 is
+returned, and ``errno`` is set appropriately. Possible error codes are:
+
+EBADF
+    ``fd`` is not a valid open file descriptor.
diff --git a/Documentation/media/uapi/mediactl/request-func-ioctl.rst b/Documentation/media/uapi/mediactl/request-func-ioctl.rst
new file mode 100644
index 000000000000..ff7b072a6999
--- /dev/null
+++ b/Documentation/media/uapi/mediactl/request-func-ioctl.rst
@@ -0,0 +1,67 @@
+.. SPDX-License-Identifier: GPL-2.0 OR GFDL-1.1-or-later WITH no-invariant-sections
+
+.. _request-func-ioctl:
+
+***************
+request ioctl()
+***************
+
+Name
+====
+
+request-ioctl - Control a request file descriptor
+
+
+Synopsis
+========
+
+.. code-block:: c
+
+    #include <sys/ioctl.h>
+
+
+.. c:function:: int ioctl( int fd, int cmd, void *argp )
+    :name: req-ioctl
+
+Arguments
+=========
+
+``fd``
+    File descriptor returned by :ref:`MEDIA_IOC_REQUEST_ALLOC`.
+
+``cmd``
+    The request ioctl command code as defined in the media.h header file, for
+    example :ref:`MEDIA_REQUEST_IOC_QUEUE`.
+
+``argp``
+    Pointer to a request-specific structure.
+
+
+Description
+===========
+
+The :ref:`ioctl() <request-func-ioctl>` function manipulates request
+parameters. The argument ``fd`` must be an open file descriptor.
+
+The ioctl ``cmd`` code specifies the request function to be called. It
+has encoded in it whether the argument is an input, output or read/write
+parameter, and the size of the argument ``argp`` in bytes.
+
+Macros and structures definitions specifying request ioctl commands and
+their parameters are located in the media.h header file. All request ioctl
+commands, their respective function and parameters are specified in
+:ref:`media-user-func`.
+
+
+Return Value
+============
+
+On success 0 is returned, on error -1 and the ``errno`` variable is set
+appropriately. The generic error codes are described at the
+:ref:`Generic Error Codes <gen-errors>` chapter.
+
+Command-specific error codes are listed in the individual command
+descriptions.
+
+When an ioctl that takes an output or read/write parameter fails, the
+parameter remains unmodified.
diff --git a/Documentation/media/uapi/mediactl/request-func-poll.rst b/Documentation/media/uapi/mediactl/request-func-poll.rst
new file mode 100644
index 000000000000..85191254f381
--- /dev/null
+++ b/Documentation/media/uapi/mediactl/request-func-poll.rst
@@ -0,0 +1,77 @@
+.. SPDX-License-Identifier: GPL-2.0 OR GFDL-1.1-or-later WITH no-invariant-sections
+
+.. _request-func-poll:
+
+**************
+request poll()
+**************
+
+Name
+====
+
+request-poll - Wait for some event on a file descriptor
+
+
+Synopsis
+========
+
+.. code-block:: c
+
+    #include <sys/poll.h>
+
+
+.. c:function:: int poll( struct pollfd *ufds, unsigned int nfds, int timeout )
+   :name: request-poll
+
+Arguments
+=========
+
+``ufds``
+   List of file descriptor events to be watched
+
+``nfds``
+   Number of file descriptor events at the \*ufds array
+
+``timeout``
+   Timeout to wait for events
+
+
+Description
+===========
+
+With the :c:func:`poll() <request-func-poll>` function applications can wait
+for a request to complete.
+
+On success :c:func:`poll() <request-func-poll>` returns the number of file
+descriptors that have been selected (that is, file descriptors for which the
+``revents`` field of the respective struct :c:type:`pollfd`
+is non-zero). Request file descriptor set the ``POLLPRI`` flag in ``revents``
+when the request was completed.  When the function times out it returns
+a value of zero, on failure it returns -1 and the ``errno`` variable is
+set appropriately.
+
+Attempting to poll for a request that is not yet queued will
+set the ``POLLERR`` flag in ``revents``.
+
+
+Return Value
+============
+
+On success, :c:func:`poll() <request-func-poll>` returns the number of
+structures which have non-zero ``revents`` fields, or zero if the call
+timed out. On error -1 is returned, and the ``errno`` variable is set
+appropriately:
+
+``EBADF``
+    One or more of the ``ufds`` members specify an invalid file
+    descriptor.
+
+``EFAULT``
+    ``ufds`` references an inaccessible memory area.
+
+``EINTR``
+    The call was interrupted by a signal.
+
+``EINVAL``
+    The ``nfds`` value exceeds the ``RLIMIT_NOFILE`` value. Use
+    ``getrlimit()`` to obtain this value.