This ioctl call returns a frontend event if available. If an event is
not available, the behavior depends on whether the device is in blocking
or non-blocking mode. In the latter case, the call fails immediately
-with errno set to EWOULDBLOCK. In the former case, the call blocks until
+with errno set to ``EWOULDBLOCK``. In the former case, the call blocks until
an event becomes available.
SYNOPSIS
- .. row 1
- - EWOULDBLOCK
+ - ``EWOULDBLOCK``
- There is no event pending, and the device is in non-blocking mode.
- .. row 2
- - EOVERFLOW
+ - ``EOVERFLOW``
- Overflow in event queue - one or more events were lost.
- .. row 1
- - EINVAL
+ - ``EINVAL``
- Maximum supported symbol rate reached.
- .. row 1
- - EINVAL
+ - ``EINVAL``
- Maximum supported symbol rate reached.
- .. row 1
- - ENODEV
+ - ``ENODEV``
- Device driver not loaded/available.
- .. row 2
- - EBUSY
+ - ``EBUSY``
- Device or resource busy.
- .. row 3
- - EINVAL
+ - ``EINVAL``
- Invalid argument.
- .. row 1
- - EBADF
+ - ``EBADF``
- fd is not a valid open file descriptor.
- .. row 1
- - EPERM
+ - ``EPERM``
- Mode AUDIO_SOURCE_MEMORY not selected.
- .. row 2
- - ENOMEM
+ - ``ENOMEM``
- Attempted to write more data than the internal buffer can hold.
- .. row 3
- - EBADF
+ - ``EBADF``
- fd is not a valid open file descriptor.
- .. row 1
- - EINVAL
+ - ``EINVAL``
- type is not a valid or supported stream type.
- .. row 1
- - EINVAL
+ - ``EINVAL``
- id is not a valid id.
- .. row 1
- - EINVAL
+ - ``EINVAL``
- attr is not a valid or supported attribute setting.
- .. row 1
- - EINVAL
+ - ``EINVAL``
- karaoke is not a valid or supported karaoke setting.
- .. row 1
- - ENODEV
+ - ``ENODEV``
- Device driver not loaded/available.
- .. row 2
- - EINTERNAL
+ - ``EINTERNAL``
- Internal error.
- .. row 3
- - EBUSY
+ - ``EBUSY``
- Device or resource busy.
- .. row 4
- - EINVAL
+ - ``EINVAL``
- Invalid argument.
- .. row 1
- - EBADF
+ - ``EBADF``
- fd is not a valid open file descriptor.
- .. row 1
- - ENODEV
+ - ``ENODEV``
- Device driver not loaded/available.
- .. row 2
- - EINVAL
+ - ``EINVAL``
- Invalid argument.
- .. row 3
- - EMFILE
+ - ``EMFILE``
- “Too many open files”, i.e. no more filters available.
- .. row 4
- - ENOMEM
+ - ``ENOMEM``
- The driver failed to allocate enough memory.
- .. row 1
- - EBADF
+ - ``EBADF``
- fd is not a valid open file descriptor.
- .. row 1
- - EWOULDBLOCK
+ - ``EWOULDBLOCK``
- No data to return and O_NONBLOCK was specified.
- .. row 2
- - EBADF
+ - ``EBADF``
- fd is not a valid open file descriptor.
- .. row 3
- - ECRC
+ - ``ECRC``
- Last section had a CRC error - no data returned. The buffer is
flushed.
- .. row 4
- - EOVERFLOW
+ - ``EOVERFLOW``
-
- .. row 6
- - ETIMEDOUT
+ - ``ETIMEDOUT``
- The section was not loaded within the stated timeout period. See
ioctl DMX_SET_FILTER for how to set a timeout.
- .. row 7
- - EFAULT
+ - ``EFAULT``
- The driver failed to write to the callers buffer due to an invalid
*buf pointer.
- .. row 1
- - EWOULDBLOCK
+ - ``EWOULDBLOCK``
- No data was written. This might happen if O_NONBLOCK was
specified and there is no more buffer space available (if
- .. row 2
- - EBUSY
+ - ``EBUSY``
- This error code indicates that there are conflicting requests. The
corresponding demux device is setup to receive data from the
- .. row 3
- - EBADF
+ - ``EBADF``
- fd is not a valid open file descriptor.
- .. row 1
- - EINVAL
+ - ``EINVAL``
- Invalid argument, i.e. no filtering parameters provided via the
DMX_SET_FILTER or DMX_SET_PES_FILTER functions.
- .. row 2
- - EBUSY
+ - ``EBUSY``
- This error code indicates that there are conflicting requests.
There are active filters filtering data from another input source.
- .. row 1
- - EBUSY
+ - ``EBUSY``
- This error code indicates that there are conflicting requests.
There are active filters filtering data from another input source.
This ioctl call returns an event if available. If an event is not
available, the behavior depends on whether the device is in blocking or
non-blocking mode. In the latter case, the call fails immediately with
-errno set to EWOULDBLOCK. In the former case, the call blocks until an
+errno set to ``EWOULDBLOCK``. In the former case, the call blocks until an
event becomes available.
SYNOPSIS
- .. row 1
- - EWOULDBLOCK
+ - ``EWOULDBLOCK``
- There is no event pending, and the device is in non-blocking mode.
- .. row 1
- - EINVAL
+ - ``EINVAL``
- Invalid stc number.
allowed.
When the ``O_NONBLOCK`` flag is given, the system calls may return
- EAGAIN error code when no data is available or when the device
+ ``EAGAIN`` error code when no data is available or when the device
driver is temporarily busy.
Other flags have no effect.
- .. row 1
- - ENODEV
+ - ``ENODEV``
- Device driver not loaded/available.
- .. row 2
- - EINTERNAL
+ - ``EINTERNAL``
- Internal error.
- .. row 3
- - EBUSY
+ - ``EBUSY``
- Device or resource busy.
- .. row 4
- - EINVAL
+ - ``EINVAL``
- Invalid argument.
- .. row 1
- - EBADF
+ - ``EBADF``
- fd is not a valid open file descriptor.
- .. row 1
- - EPERM
+ - ``EPERM``
- Mode VIDEO_SOURCE_MEMORY not selected.
- .. row 2
- - ENOMEM
+ - ``ENOMEM``
- Attempted to write more data than the internal buffer can hold.
- .. row 3
- - EBADF
+ - ``EBADF``
- fd is not a valid open file descriptor.
This ioctl call returns an event of type video_event if available. If
an event is not available, the behavior depends on whether the device is
in blocking or non-blocking mode. In the latter case, the call fails
-immediately with errno set to EWOULDBLOCK. In the former case, the call
+immediately with errno set to ``EWOULDBLOCK``. In the former case, the call
blocks until an event becomes available. The standard Linux poll()
and/or select() system calls can be used with the device file descriptor
to watch for new events. For select(), the file descriptor should be
- .. row 1
- - EWOULDBLOCK
+ - ``EWOULDBLOCK``
- There is no event pending, and the device is in non-blocking mode.
- .. row 2
- - EOVERFLOW
+ - ``EOVERFLOW``
- Overflow in event queue - one or more events were lost.
- .. row 1
- - EPERM
+ - ``EPERM``
- Mode VIDEO_SOURCE_MEMORY not selected.
- .. row 1
- - EPERM
+ - ``EPERM``
- Mode VIDEO_SOURCE_MEMORY not selected.
- .. row 1
- - EINVAL
+ - ``EINVAL``
- Invalid sub-stream id.
- .. row 1
- - EINVAL
+ - ``EINVAL``
- format is not a valid video format.
- .. row 1
- - EINVAL
+ - ``EINVAL``
- system is not a valid or supported video system.
- .. row 1
- - EINVAL
+ - ``EINVAL``
- input is not a valid spu setting or driver cannot handle SPU.
- .. row 1
- - EINVAL
+ - ``EINVAL``
- input is not a valid palette or driver doesn’t handle SPU.
- .. row 1
- - EFAULT
+ - ``EFAULT``
- driver is not able to return navigational information
- .. row 1
- - EINVAL
+ - ``EINVAL``
- input is not a valid attribute setting.
:ref:`VIDIOC_QUERYCAP` ioctl.
Ioctls changing driver properties, such as
-:ref:`VIDIOC_S_INPUT <VIDIOC_G_INPUT>`, return an EBUSY error code
+:ref:`VIDIOC_S_INPUT <VIDIOC_G_INPUT>`, return an ``EBUSY`` error code
after another application obtained higher priority.
the driver will set the ``bytesused`` field to 0, regardless of
the format. Any Any subsequent call to the
:ref:`VIDIOC_DQBUF <VIDIOC_QBUF>` ioctl will not block anymore,
- but return an EPIPE error code.
+ but return an ``EPIPE`` error code.
- .. row 13
prohibits different image and frame buffer formats, the format requested
first takes precedence. The attempt to capture
(:ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>`) or overlay
-(:ref:`VIDIOC_S_FBUF <VIDIOC_G_FBUF>`) may fail with an EBUSY error
+(:ref:`VIDIOC_S_FBUF <VIDIOC_G_FBUF>`) may fail with an ``EBUSY`` error
code or return accordingly modified parameters..
When simultaneous capturing and overlay is supported and the hardware
prohibits different image and window sizes, the size requested first
takes precedence. The attempt to capture or overlay as well
-(:ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>`) may fail with an EBUSY error
+(:ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>`) may fail with an ``EBUSY`` error
code or return accordingly modified parameters.
fields of the struct :ref:`v4l2_vbi_format <v4l2-vbi-format>`
``vbi`` member of the ``fmt`` union, or better just modify the results
of :ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>`, and call the :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>`
-ioctl with a pointer to this structure. Drivers return an EINVAL error
+ioctl with a pointer to this structure. Drivers return an ``EINVAL`` error
code only when the given parameters are ambiguous, otherwise they modify
the parameters according to the hardware capabilities and return the
actual parameters. When the driver allocates resources at this point, it
-may return an EBUSY error code to indicate the returned parameters are
+may return an ``EBUSY`` error code to indicate the returned parameters are
valid but the required resources are currently not available. That may
happen for instance when the video and VBI areas to capture would
overlap, or when the driver supports multiple opens and another process
already requested VBI capturing or output. Anyway, applications must
-expect other resource allocation points which may return EBUSY, at the
+expect other resource allocation points which may return ``EBUSY``, at the
:ref:`VIDIOC_STREAMON` ioctl and the first read(),
write() and select() call.
Remember the :ref:`VIDIOC_STREAMON` ioctl and the
first read(), write() and select() call can be resource allocation
-points returning an EBUSY error code if the required hardware resources
+points returning an ``EBUSY`` error code if the required hardware resources
are temporarily unavailable, for example the device is already in use by
another process.
The :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl modifies the parameters
according to hardware capabilities. When the driver allocates resources
-at this point, it may return an EBUSY error code if the required
+at this point, it may return an ``EBUSY`` error code if the required
resources are temporarily unavailable. Other resource allocation points
-which may return EBUSY can be the
+which may return ``EBUSY`` can be the
:ref:`VIDIOC_STREAMON` ioctl and the first
:ref:`read() <func-read>`, :ref:`write() <func-write>` and
:ref:`select() <func-select>` call.
- :cspan:`2` Set of services applicable to 625 line systems.
-Drivers may return an EINVAL error code when applications attempt to
+Drivers may return an ``EINVAL`` error code when applications attempt to
read or write data without prior format negotiation, after switching the
video standard (which may invalidate the negotiated VBI parameters) and
after switching the video input (which may change the video standard as
a side effect). The :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl may
-return an EBUSY error code when applications attempt to change the
+return an ``EBUSY`` error code when applications attempt to change the
format while i/o is in progress (between a
:ref:`VIDIOC_STREAMON` and
:ref:`VIDIOC_STREAMOFF <VIDIOC_STREAMON>` call, and after the first
Packets are always passed in ascending line number order, without
duplicate line numbers. The :ref:`write() <func-write>` function and
-the :ref:`VIDIOC_QBUF` ioctl must return an EINVAL
+the :ref:`VIDIOC_QBUF` ioctl must return an ``EINVAL``
error code when applications violate this rule. They must also return an
EINVAL error code when applications pass an incorrect field or line
number, or a combination of ``field``, ``line`` and ``id`` which has not
Applications are responsible for configuring coherent parameters on the
whole pipeline and making sure that connected pads have compatible
formats. The pipeline is checked for formats mismatch at
-:ref:`VIDIOC_STREAMON` time, and an EPIPE error
+:ref:`VIDIOC_STREAMON` time, and an ``EPIPE`` error
code is then returned if the configuration is invalid.
Pad-level image format configuration support can be tested by calling
the :ref:`VIDIOC_SUBDEV_G_FMT` ioctl on pad
-0. If the driver returns an EINVAL error code pad-level format
+0. If the driver returns an ``EINVAL`` error code pad-level format
configuration is not supported by the sub-device.
V4L2 drivers *may* support multiple opens, see :ref:`open` for details
and consequences.
-V4L drivers respond to V4L2 ioctls with an EINVAL error code.
+V4L drivers respond to V4L2 ioctls with an ``EINVAL`` error code.
Querying Capabilities
- Applications can call the :ref:`VIDIOC_G_CROP <VIDIOC_G_CROP>`
ioctl to determine if the device supports capturing a subsection
of the full picture ("cropping" in V4L2). If not, the ioctl
- returns the EINVAL error code. For more information on cropping
+ returns the ``EINVAL`` error code. For more information on cropping
and scaling see :ref:`crop`.
- .. row 12
- The ``VIDIOCMCAPTURE`` ioctl prepares a buffer for capturing. It
also determines the image format for this buffer. The ioctl
- returns immediately, eventually with an EAGAIN error code if no
+ returns immediately, eventually with an ``EAGAIN`` error code if no
video signal had been detected. When the driver supports more than
one buffer applications can call the ioctl multiple times and thus
have multiple outstanding capture requests.
Apparently only the Zoran (ZR 36120) driver implements these ioctls. The
semantics differ from those specified for V4L2 in two ways. The
parameters are reset on :ref:`open() <func-open>` and
-``VIDIOCSVBIFMT`` always returns an EINVAL error code if the parameters
+``VIDIOCSVBIFMT`` always returns an ``EINVAL`` error code if the parameters
are invalid.
more buffers can be dequeued. By default ``VIDIOC_DQBUF`` blocks when no
buffer is in the outgoing queue. When the ``O_NONBLOCK`` flag was given
to the :ref:`open() <func-open>` function, ``VIDIOC_DQBUF`` returns
-immediately with an EAGAIN error code when no buffer is available. The
+immediately with an ``EAGAIN`` error code when no buffer is available. The
:ref:`select() <func-select>` and :ref:`poll() <func-poll>`
functions are always available.
devices only writing.
When the ``O_NONBLOCK`` flag is given, the read() function and the
- :ref:`VIDIOC_DQBUF <VIDIOC_QBUF>` ioctl will return the EAGAIN
+ :ref:`VIDIOC_DQBUF <VIDIOC_QBUF>` ioctl will return the ``EAGAIN``
error code when no data is available or no buffer is in the driver
outgoing queue, otherwise these functions block until data becomes
available. All V4L2 drivers exchanging data with applications must
By default :c:func:`read()` blocks until data becomes available. When
the ``O_NONBLOCK`` flag was given to the :ref:`open() <func-open>`
-function it returns immediately with an EAGAIN error code when no data
+function it returns immediately with an ``EAGAIN`` error code when no data
is available. The :ref:`select() <func-select>` or
:ref:`poll() <func-poll>` functions can always be used to suspend
execution until data becomes available. All drivers supporting the
- .. row 1
- - EAGAIN (aka EWOULDBLOCK)
+ - ``EAGAIN`` (aka ``EWOULDBLOCK``)
- The ioctl can't be handled because the device is in state where it
can't perform it. This could happen for example in case where
- .. row 2
- - EBADF
+ - ``EBADF``
- The file descriptor is not a valid.
- .. row 3
- - EBUSY
+ - ``EBUSY``
- The ioctl can't be handled because the device is busy. This is
typically return while device is streaming, and an ioctl tried to
- .. row 4
- - EFAULT
+ - ``EFAULT``
- There was a failure while copying data from/to userspace, probably
caused by an invalid pointer reference.
- .. row 5
- - EINVAL
+ - ``EINVAL``
- One or more of the ioctl parameters are invalid or out of the
allowed range. This is a widely used error code. See the
- .. row 6
- - ENODEV
+ - ``ENODEV``
- Device not found or was removed.
- .. row 7
- - ENOMEM
+ - ``ENOMEM``
- There's not enough memory to handle the desired operation.
- .. row 8
- - ENOTTY
+ - ``ENOTTY``
- The ioctl is not supported by the driver, actually meaning that
the required functionality is not available, or the file
- .. row 9
- - ENOSPC
+ - ``ENOSPC``
- On USB devices, the stream ioctl's can return this error, meaning
that this request would overcommit the usb bandwidth reserved for
- .. row 10
- - EPERM
+ - ``EPERM``
- Permission denied. Can be returned if the device needs write
permission, or some special capabilities is needed (e. g. root)
transmitted only on the first field. The comment that both ``count``
values will usually be equal is misleading and pointless and has been
removed. This change *breaks compatibility* with earlier versions:
- Drivers may return EINVAL, applications may not function correctly.
+ Drivers may return ``EINVAL``, applications may not function correctly.
3. Drivers are again permitted to return negative (unknown) start values
as proposed earlier. Why this feature was dropped is unclear. This
change may *break compatibility* with applications depending on the
start values being positive. The use of ``EBUSY`` and ``EINVAL``
error codes with the :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl was
- clarified. The EBUSY error code was finally documented, and the
+ clarified. The ``EBUSY`` error code was finally documented, and the
``reserved2`` field which was previously mentioned only in the
``videodev.h`` header file.
3. The struct :ref:`v4l2_capability <v4l2-capability>` changed
dramatically. Note that also the size of the structure changed,
which is encoded in the ioctl request code, thus older V4L2 devices
- will respond with an EINVAL error code to the new
+ will respond with an ``EINVAL`` error code to the new
:ref:`VIDIOC_QUERYCAP` ioctl.
There are new fields to identify the driver, a new RDS device
4. The documentation of the :ref:`VIDIOC_QBUF` and
:ref:`VIDIOC_DQBUF <VIDIOC_QBUF>` ioctls did not mention the
struct :ref:`v4l2_buffer <v4l2-buffer>` ``memory`` field. It was
- also missing from examples. Also on the ``VIDIOC_DQBUF`` page the EIO
+ also missing from examples. Also on the ``VIDIOC_DQBUF`` page the ``EIO``
error code was not documented.
The data must start and end with a pulse, therefore, the data must
always include an uneven number of samples. The write function must
block until the data has been transmitted by the hardware. If more data
-is provided than the hardware can send, the driver returns EINVAL.
+is provided than the hardware can send, the driver returns ``EINVAL``.
.. ------------------------------------------------------------------------------
Entities can be enumerated by or'ing the id with the
``MEDIA_ENT_ID_FLAG_NEXT`` flag. The driver will return information
about the entity with the smallest id strictly larger than the requested
-one ('next entity'), or the EINVAL error code if there is none.
+one ('next entity'), or the ``EINVAL`` error code if there is none.
Entity IDs can be non-contiguous. Applications must *not* try to
enumerate entities by calling MEDIA_IOC_ENUM_ENTITIES with increasing
Link configuration has no side effect on other links. If an enabled link
at the sink pad prevents the link from being enabled, the driver returns
-with an EBUSY error code.
+with an ``EBUSY`` error code.
Only links marked with the ``DYNAMIC`` link flag can be enabled/disabled
while streaming media data. Attempting to enable or disable a streaming
-non-dynamic link will return an EBUSY error code.
+non-dynamic link will return an ``EBUSY`` error code.
-If the specified link can't be found the driver returns with an EINVAL
+If the specified link can't be found the driver returns with an ``EINVAL``
error code.
dequeued. By default ``VIDIOC_DQBUF`` blocks when no buffer is in the
outgoing queue. When the ``O_NONBLOCK`` flag was given to the
:ref:`open() <func-open>` function, ``VIDIOC_DQBUF`` returns
-immediately with an EAGAIN error code when no buffer is available. The
+immediately with an ``EAGAIN`` error code when no buffer is available. The
:ref:`select() <func-select>` or :ref:`poll() <func-poll>` functions
are always available.
.. [1]
There are still some old and obscure drivers that have not been
updated to allow for multiple opens. This implies that for such
- drivers :ref:`open() <func-open>` can return an EBUSY error code
+ drivers :ref:`open() <func-open>` can return an ``EBUSY`` error code
when the device is already in use.
.. [2]
will return the V4L2 API version used by the driver, with generally
matches the Kernel version. There's no need of using
:ref:`VIDIOC_QUERYCAP` to check if a specific ioctl
-is supported, the V4L2 core now returns ENOTTY if a driver doesn't
+is supported, the V4L2 core now returns ``ENOTTY`` if a driver doesn't
provide support for an ioctl.
Other features can be queried by calling the respective ioctl, for
Writing "none" will disable all protocols.
-Write fails with EINVAL if an invalid protocol combination or unknown
+Write fails with ``EINVAL`` if an invalid protocol combination or unknown
protocol name is used.
Writing "none" will disable wakeup.
-Write fails with EINVAL if an invalid protocol combination or unknown
+Write fails with ``EINVAL`` if an invalid protocol combination or unknown
protocol name is used, or if wakeup is not supported by the hardware.
:ref:`v4l2_input <v4l2-input>` and struct
:ref:`v4l2_output <v4l2-output>` to zero and the :ref:`VIDIOC_G_STD <VIDIOC_G_STD>`,
:ref:`VIDIOC_S_STD <VIDIOC_G_STD>`, :ref:`VIDIOC_QUERYSTD` and :ref:`VIDIOC_ENUMSTD` ioctls
-shall return the ENOTTY error code or the EINVAL error code.
+shall return the ``ENOTTY`` error code or the ``EINVAL`` error code.
Applications can make use of the :ref:`input-capabilities` and
:ref:`output-capabilities` flags to determine whether the video
devices.
These ioctls are optional, drivers need not implement them. If so, they
-return the EINVAL error code.
+return the ``EINVAL`` error code.
.. ------------------------------------------------------------------------------
more buffers can be dequeued. By default ``VIDIOC_DQBUF`` blocks when no
buffer is in the outgoing queue. When the ``O_NONBLOCK`` flag was given
to the :ref:`open() <func-open>` function, ``VIDIOC_DQBUF`` returns
-immediately with an EAGAIN error code when no buffer is available. The
+immediately with an ``EAGAIN`` error code when no buffer is available. The
:ref:`select() <func-select>` or :ref:`poll() <func-poll>` function
are always available.
:ref:`VIDIOC_CREATE_BUFS` will set ``index`` to the current number of
created buffers, and it will check the validity of ``memory`` and
``format.type``. If those are invalid -1 is returned and errno is
- set to EINVAL error code, otherwise :ref:`VIDIOC_CREATE_BUFS` returns
- 0. It will never set errno to EBUSY error code in this particular
+ set to ``EINVAL`` error code, otherwise :ref:`VIDIOC_CREATE_BUFS` returns
+ 0. It will never set errno to ``EBUSY`` error code in this particular
case.
- .. row 3
When ``match.type`` is ``V4L2_CHIP_MATCH_BRIDGE``, ``match.addr``
selects the nth bridge 'chip' on the TV card. You can enumerate all
chips by starting at zero and incrementing ``match.addr`` by one until
-:ref:`VIDIOC_DBG_G_CHIP_INFO` fails with an EINVAL error code. The number
+:ref:`VIDIOC_DBG_G_CHIP_INFO` fails with an ``EINVAL`` error code. The number
zero always selects the bridge chip itself, e. g. the chip connected to
the PCI or USB bus. Non-zero numbers identify specific parts of the
bridge chip such as an AC97 register block.
indicated by the driver setting the ``bytesused`` field to 0. Once
the ``V4L2_BUF_FLAG_LAST`` flag was set, the
:ref:`VIDIOC_DQBUF <VIDIOC_QBUF>` ioctl will not block anymore,
- but return an EPIPE error code. If
+ but return an ``EPIPE`` error code. If
``V4L2_DEC_CMD_STOP_IMMEDIATELY`` is set, then the decoder stops
immediately (ignoring the ``pts`` value), otherwise it will keep
decoding until timestamp >= pts or until the last of the pending
- 2
- Pause the decoder. When the decoder has not been started yet, the
- driver will return an EPERM error code. When the decoder is
+ driver will return an ``EPERM`` error code. When the decoder is
already paused, this command does nothing. This command has one
flag: if ``V4L2_DEC_CMD_PAUSE_TO_BLACK`` is set, then set the
decoder output to black when paused.
- 3
- Resume decoding after a PAUSE command. When the decoder has not
- been started yet, the driver will return an EPERM error code. When
+ been started yet, the driver will return an ``EPERM`` error code. When
the decoder is already running, this command does nothing. No
flags are defined for this command.
the desired pad number in the struct
:ref:`v4l2_dv_timings_cap <v4l2-dv-timings-cap>` ``pad`` field and
zero the ``reserved`` array. Attempts to query capabilities on a pad
-that doesn't support them will return an EINVAL error code.
+that doesn't support them will return an ``EINVAL`` error code.
.. _v4l2-bt-timings-cap:
driver setting the ``bytesused`` field to 0. Once the
``V4L2_BUF_FLAG_LAST`` flag was set, the
:ref:`VIDIOC_DQBUF <VIDIOC_QBUF>` ioctl will not block anymore,
- but return an EPIPE error code.
+ but return an ``EPIPE`` error code.
- .. row 3
- 2
- Pause the encoder. When the encoder has not been started yet, the
- driver will return an EPERM error code. When the encoder is
+ driver will return an ``EPERM`` error code. When the encoder is
already paused, this command does nothing. No flags are defined
for this command.
- 3
- Resume encoding after a PAUSE command. When the encoder has not
- been started yet, the driver will return an EPERM error code. When
+ been started yet, the driver will return an ``EPERM`` error code. When
the encoder is already running, this command does nothing. No
flags are defined for this command.
field, set the ``pad`` field to 0, zero the reserved array of struct
:ref:`v4l2_enum_dv_timings <v4l2-enum-dv-timings>` and call the
``VIDIOC_ENUM_DV_TIMINGS`` ioctl on a video node with a pointer to this
-structure. Drivers fill the rest of the structure or return an EINVAL
+structure. Drivers fill the rest of the structure or return an ``EINVAL``
error code when the index is out of bounds. To enumerate all supported
DV timings, applications shall begin at index zero, incrementing by one
-until the driver returns EINVAL. Note that drivers may enumerate a
+until the driver returns ``EINVAL``. Note that drivers may enumerate a
different set of DV timings after switching the video input or output.
When implemented by the driver DV timings of subdevices can be queried
pad number in the struct
:ref:`v4l2_enum_dv_timings <v4l2-enum-dv-timings>` ``pad`` field.
Attempts to enumerate timings on a pad that doesn't support them will
-return an EINVAL error code.
+return an ``EINVAL`` error code.
.. _v4l2-enum-dv-timings:
To enumerate image formats applications initialize the ``type`` and
``index`` field of struct :ref:`v4l2_fmtdesc <v4l2-fmtdesc>` and call
the :ref:`VIDIOC_ENUM_FMT` ioctl with a pointer to this structure. Drivers
-fill the rest of the structure or return an EINVAL error code. All
+fill the rest of the structure or return an ``EINVAL`` error code. All
formats are enumerable by beginning at index zero and incrementing by
-one until EINVAL is returned.
+one until ``EINVAL`` is returned.
Note that after switching input or output the list of enumerated image
formats may be different.
``index`` field and zero out the ``reserved`` array of a struct
:ref:`v4l2_audio <v4l2-audio>` and call the :ref:`VIDIOC_ENUMAUDIO`
ioctl with a pointer to this structure. Drivers fill the rest of the
-structure or return an EINVAL error code when the index is out of
+structure or return an ``EINVAL`` error code when the index is out of
bounds. To enumerate all audio inputs applications shall begin at index
-zero, incrementing by one until the driver returns EINVAL.
+zero, incrementing by one until the driver returns ``EINVAL``.
See :ref:`VIDIOC_G_AUDIO <VIDIOC_G_AUDIO>` for a description of struct
:ref:`v4l2_audio <v4l2-audio>`.
``index`` field and zero out the ``reserved`` array of a struct
:ref:`v4l2_audioout <v4l2-audioout>` and call the ``VIDIOC_G_AUDOUT``
ioctl with a pointer to this structure. Drivers fill the rest of the
-structure or return an EINVAL error code when the index is out of
+structure or return an ``EINVAL`` error code when the index is out of
bounds. To enumerate all audio outputs applications shall begin at index
-zero, incrementing by one until the driver returns EINVAL.
+zero, incrementing by one until the driver returns ``EINVAL``.
Note connectors on a TV card to loop back the received audio signal to a
sound card are not audio outputs in this sense.
To query the attributes of a video input applications initialize the
``index`` field of struct :ref:`v4l2_input <v4l2-input>` and call the
:ref:`VIDIOC_ENUMINPUT` ioctl with a pointer to this structure. Drivers
-fill the rest of the structure or return an EINVAL error code when the
+fill the rest of the structure or return an ``EINVAL`` error code when the
index is out of bounds. To enumerate all inputs applications shall begin
-at index zero, incrementing by one until the driver returns EINVAL.
+at index zero, incrementing by one until the driver returns ``EINVAL``.
.. _v4l2-input:
To query the attributes of a video outputs applications initialize the
``index`` field of struct :ref:`v4l2_output <v4l2-output>` and call
the :ref:`VIDIOC_ENUMOUTPUT` ioctl with a pointer to this structure.
-Drivers fill the rest of the structure or return an EINVAL error code
+Drivers fill the rest of the structure or return an ``EINVAL`` error code
when the index is out of bounds. To enumerate all outputs applications
shall begin at index zero, incrementing by one until the driver returns
EINVAL.
defined) one, applications initialize the ``index`` field of struct
:ref:`v4l2_standard <v4l2-standard>` and call the :ref:`VIDIOC_ENUMSTD`
ioctl with a pointer to this structure. Drivers fill the rest of the
-structure or return an EINVAL error code when the index is out of
+structure or return an ``EINVAL`` error code when the index is out of
bounds. To enumerate all standards applications shall begin at index
-zero, incrementing by one until the driver returns EINVAL. Drivers may
+zero, incrementing by one until the driver returns ``EINVAL``. Drivers may
enumerate a different set of standards after switching the video input
or output. [1]_
To query the current audio input applications zero out the ``reserved``
array of a struct :ref:`v4l2_audio <v4l2-audio>` and call the
:ref:`VIDIOC_G_AUDIO <VIDIOC_G_AUDIO>` ioctl with a pointer to this structure. Drivers fill
-the rest of the structure or return an EINVAL error code when the device
+the rest of the structure or return an ``EINVAL`` error code when the device
has no audio inputs, or none which combine with the current video input.
Audio inputs have one writable property, the audio mode. To select the
To query the current audio output applications zero out the ``reserved``
array of a struct :ref:`v4l2_audioout <v4l2-audioout>` and call the
``VIDIOC_G_AUDOUT`` ioctl with a pointer to this structure. Drivers fill
-the rest of the structure or return an EINVAL error code when the device
+the rest of the structure or return an ``EINVAL`` error code when the device
has no audio inputs, or none which combine with the current video
output.
``reserved`` array (which in the future may contain writable properties)
of a :c:type:`struct v4l2_audioout` structure and call the
``VIDIOC_S_AUDOUT`` ioctl. Drivers switch to the requested output or
-return the EINVAL error code when the index is out of bounds. This is a
+return the ``EINVAL`` error code when the index is out of bounds. This is a
write-only ioctl, it does not return the current audio output attributes
as ``VIDIOC_G_AUDOUT`` does.
``type`` field of a :c:type:`struct v4l2_crop` structure to the
respective buffer (stream) type and call the :ref:`VIDIOC_G_CROP <VIDIOC_G_CROP>` ioctl
with a pointer to this structure. The driver fills the rest of the
-structure or returns the EINVAL error code if cropping is not supported.
+structure or returns the ``EINVAL`` error code if cropping is not supported.
To change the cropping rectangle applications initialize the ``type``
and struct :ref:`v4l2_rect <v4l2-rect>` substructure named ``c`` of a
been negotiated.
When cropping is not supported then no parameters are changed and
-:ref:`VIDIOC_S_CROP <VIDIOC_G_CROP>` returns the EINVAL error code.
+:ref:`VIDIOC_S_CROP <VIDIOC_G_CROP>` returns the ``EINVAL`` error code.
.. _v4l2-crop:
fields of a struct :c:type:`struct v4l2_control` and call the
:ref:`VIDIOC_S_CTRL <VIDIOC_G_CTRL>` ioctl.
-When the ``id`` is invalid drivers return an EINVAL error code. When the
+When the ``id`` is invalid drivers return an ``EINVAL`` error code. When the
``value`` is out of bounds drivers can choose to take the closest valid
-value or return an ERANGE error code, whatever seems more appropriate.
+value or return an ``ERANGE`` error code, whatever seems more appropriate.
However, :ref:`VIDIOC_S_CTRL <VIDIOC_G_CTRL>` is a write-only ioctl, it does not return the
actual new value. If the ``value`` is inappropriate for the control
(e.g. if it refers to an unsupported menu index of a menu control), then
:ref:`v4l2_dv_timings <v4l2-dv-timings>`. These ioctls take a
pointer to the struct :ref:`v4l2_dv_timings <v4l2-dv-timings>`
structure as argument. If the ioctl is not supported or the timing
-values are not correct, the driver returns EINVAL error code.
+values are not correct, the driver returns ``EINVAL`` error code.
The ``linux/v4l2-dv-timings.h`` header can be used to get the timings of
the formats in the :ref:`cea861` and :ref:`vesadmt` standards. If
the current input or output does not support DV timings (e.g. if
:ref:`VIDIOC_ENUMINPUT` does not set the
-``V4L2_IN_CAP_DV_TIMINGS`` flag), then ENODATA error code is returned.
+``V4L2_IN_CAP_DV_TIMINGS`` flag), then ``ENODATA`` error code is returned.
Return Value
:ref:`VIDIOC_ENUMOUTPUT` respectively. When used
with subdevice nodes the ``pad`` field represents the input or output
pad of the subdevice. If there is no EDID support for the given ``pad``
-value, then the EINVAL error code will be returned.
+value, then the ``EINVAL`` error code will be returned.
To get the EDID data the application has to fill in the ``pad``,
``start_block``, ``blocks`` and ``edid`` fields, zero the ``reserved``
If there are fewer blocks than specified, then the driver will set
``blocks`` to the actual number of blocks. If there are no EDID blocks
-available at all, then the error code ENODATA is set.
+available at all, then the error code ``ENODATA`` is set.
If blocks have to be retrieved from the sink, then this call will block
until they have been read.
The driver assumes that the full EDID is passed in. If there are more
EDID blocks than the hardware can handle then the EDID is not written,
-but instead the error code E2BIG is set and ``blocks`` is set to the
+but instead the error code ``E2BIG`` is set and ``blocks`` is set to the
maximum that the hardware supports. If ``start_block`` is any value
-other than 0 then the error code EINVAL is set.
+other than 0 then the error code ``EINVAL`` is set.
To disable an EDID you set ``blocks`` to 0. Depending on the hardware
this will drive the hotplug pin low and/or block the source from reading
appropriately. The generic error codes are described at the
:ref:`Generic Error Codes <gen-errors>` chapter.
-ENODATA
+``ENODATA``
The EDID data is not available.
-E2BIG
+``E2BIG``
The EDID data you provided is more than the hardware can handle.
If the ``size`` is too small to receive the control result (only
relevant for pointer-type controls like strings), then the driver will
-set ``size`` to a valid value and return an ENOSPC error code. You
+set ``size`` to a valid value and return an ``ENOSPC`` error code. You
should re-allocate the memory to this new size and try again. For the
string type it is possible that the same issue occurs again if the
string has grown in the meantime. It is recommended to call
values are automatically adjusted to a valid value or if an error is
returned.
-When the ``id`` or ``which`` is invalid drivers return an EINVAL error
+When the ``id`` or ``which`` is invalid drivers return an ``EINVAL`` error
code. When the value is out of bounds drivers can choose to take the
-closest valid value or return an ERANGE error code, whatever seems more
+closest valid value or return an ``ERANGE`` error code, whatever seems more
appropriate. In the first case the new value is set in struct
:ref:`v4l2_ext_control <v4l2-ext-control>`. If the new control value
is inappropriate (e.g. the given menu index is not supported by the menu
-control), then this will also result in an EINVAL error code error.
+control), then this will also result in an ``EINVAL`` error code error.
The driver will only set/get these controls if all control values are
correct. This prevents the situation where only some of the controls
size of the memory containing the payload, or that will receive
the payload. If :ref:`VIDIOC_G_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` finds that this value is
less than is required to store the payload result, then it is set
- to a value large enough to store the payload result and ENOSPC is
+ to a value large enough to store the payload result and ``ENOSPC`` is
returned. Note that for string controls this ``size`` field should
not be confused with the length of the string. This field refers
to the size of the memory that contains the string. The actual
:ref:`v4l2_pix_format <v4l2-pix-format>` ``pix`` or the struct
:ref:`v4l2_pix_format_mplane <v4l2-pix-format-mplane>` ``pix_mp``
member. When the requested buffer type is not supported drivers return
-an EINVAL error code.
+an ``EINVAL`` error code.
To change the current format parameters applications initialize the
``type`` field and all fields of the respective ``fmt`` union member.
ioctl. When the requested buffer type is not supported drivers return an
EINVAL error code on a :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` attempt. When I/O is already in
progress or the resource is not available for other reasons drivers
-return the EBUSY error code.
+return the ``EBUSY`` error code.
The :ref:`VIDIOC_TRY_FMT <VIDIOC_G_FMT>` ioctl is equivalent to :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` with one
exception: it does not change driver state. It can also be called at any
-time, never returning EBUSY. This function is provided to negotiate
+time, never returning ``EBUSY``. This function is provided to negotiate
parameters, to learn about hardware limitations, without disabling I/O
or possibly time consuming hardware preparations. Although strongly
recommended drivers are not required to implement this ioctl.
:ref:`VIDIOC_G_INPUT <VIDIOC_G_INPUT>` ioctl with a pointer to an integer where the driver
stores the number of the input, as in the struct
:ref:`v4l2_input <v4l2-input>` ``index`` field. This ioctl will fail
-only when there are no video inputs, returning EINVAL.
+only when there are no video inputs, returning ``EINVAL``.
To select a video input applications store the number of the desired
input in an integer and call the :ref:`VIDIOC_S_INPUT <VIDIOC_G_INPUT>` ioctl with a pointer
``index`` field and zero out the ``reserved`` array of a struct
:ref:`v4l2_modulator <v4l2-modulator>` and call the
:ref:`VIDIOC_G_MODULATOR <VIDIOC_G_MODULATOR>` ioctl with a pointer to this structure. Drivers
-fill the rest of the structure or return an EINVAL error code when the
+fill the rest of the structure or return an ``EINVAL`` error code when the
index is out of bounds. To enumerate all modulators applications shall
begin at index zero, incrementing by one until the driver returns
EINVAL.
``V4L2_TUNER_SUB_SAP``. If the hardware does not support the
respective audio matrix, or the current video standard does not
permit bilingual audio the :ref:`VIDIOC_S_MODULATOR <VIDIOC_G_MODULATOR>` ioctl shall
- return an EINVAL error code and the driver shall fall back to mono
+ return an ``EINVAL`` error code and the driver shall fall back to mono
or stereo mode.
- .. row 4
``V4L2_TUNER_SUB_MONO`` or ``V4L2_TUNER_SUB_STEREO``. If the
hardware does not support the respective audio matrix, or the
current video standard does not permit SAP the
- :ref:`VIDIOC_S_MODULATOR <VIDIOC_G_MODULATOR>` ioctl shall return an EINVAL error code and
+ :ref:`VIDIOC_S_MODULATOR <VIDIOC_G_MODULATOR>` ioctl shall return an ``EINVAL`` error code and
driver shall fall back to mono or stereo mode.
- .. row 6
:ref:`VIDIOC_G_OUTPUT <VIDIOC_G_OUTPUT>` ioctl with a pointer to an integer where the driver
stores the number of the output, as in the struct
:ref:`v4l2_output <v4l2-output>` ``index`` field. This ioctl will
-fail only when there are no video outputs, returning the EINVAL error
+fail only when there are no video outputs, returning the ``EINVAL`` error
code.
To select a video output applications store the number of the desired
contains the adjusted rectangle. When the parameters are unsuitable the
application may modify the cropping (composing) or image parameters and
repeat the cycle until satisfactory parameters have been negotiated. If
-constraints flags have to be violated at then ERANGE is returned. The
+constraints flags have to be violated at then ``ERANGE`` is returned. The
error indicates that *there exist no rectangle* that satisfies the
constraints.
output device, applications initialize the ``type`` field of a struct
:ref:`v4l2_sliced_vbi_cap <v4l2-sliced-vbi-cap>`, clear the
``reserved`` array and call the :ref:`VIDIOC_G_SLICED_VBI_CAP <VIDIOC_G_SLICED_VBI_CAP>` ioctl. The
-driver fills in the remaining fields or returns an EINVAL error code if
+driver fills in the remaining fields or returns an ``EINVAL`` error code if
the sliced VBI API is unsupported or ``type`` is invalid.
Note the ``type`` field was added, and the ioctl changed from read-only
:ref:`VIDIOC_S_STD <VIDIOC_G_STD>` accepts one or more flags, being a write-only ioctl it
does not return the actual new standard as :ref:`VIDIOC_G_STD <VIDIOC_G_STD>` does. When
no flags are given or the current input does not support the requested
-standard the driver returns an EINVAL error code. When the standard set
-is ambiguous drivers may return EINVAL or choose any of the requested
+standard the driver returns an ``EINVAL`` error code. When the standard set
+is ambiguous drivers may return ``EINVAL`` or choose any of the requested
standards. If the current input or output does not support standard
video timings (e.g. if :ref:`VIDIOC_ENUMINPUT`
-does not set the ``V4L2_IN_CAP_STD`` flag), then ENODATA error code is
+does not set the ``V4L2_IN_CAP_STD`` flag), then ``ENODATA`` error code is
returned.
field and zero out the ``reserved`` array of a struct
:ref:`v4l2_tuner <v4l2-tuner>` and call the ``VIDIOC_G_TUNER`` ioctl
with a pointer to this structure. Drivers fill the rest of the structure
-or return an EINVAL error code when the index is out of bounds. To
+or return an ``EINVAL`` error code when the index is out of bounds. To
enumerate all tuners applications shall begin at index zero,
-incrementing by one until the driver returns EINVAL.
+incrementing by one until the driver returns ``EINVAL``.
Tuners have two writable properties, the audio mode and the radio
frequency. To change the audio mode, applications initialize the
By default ``VIDIOC_DQBUF`` blocks when no buffer is in the outgoing
queue. When the ``O_NONBLOCK`` flag was given to the
:ref:`open() <func-open>` function, ``VIDIOC_DQBUF`` returns
-immediately with an EAGAIN error code when no buffer is available.
+immediately with an ``EAGAIN`` error code when no buffer is available.
The :c:type:`struct v4l2_buffer` structure is specified in
:ref:`buffer`.
If the timings could not be detected because there was no signal, then
ENOLINK is returned. If a signal was detected, but it was unstable and
-the receiver could not lock to the signal, then ENOLCK is returned. If
+the receiver could not lock to the signal, then ``ENOLCK`` is returned. If
the receiver could lock to the signal, but the format is unsupported
(e.g. because the pixelclock is out of range of the hardware
capabilities), then the driver fills in whatever timings it could find
-and returns ERANGE. In that case the application can call
+and returns ``ERANGE``. In that case the application can call
:ref:`VIDIOC_DV_TIMINGS_CAP` to compare the
found timings with the hardware's capabilities in order to give more
precise feedback to the user.
information about driver and hardware capabilities. The ioctl takes a
pointer to a struct :ref:`v4l2_capability <v4l2-capability>` which is
filled by the driver. When the driver is not compatible with this
-specification the ioctl returns an EINVAL error code.
+specification the ioctl returns an ``EINVAL`` error code.
.. _v4l2-capability:
To query the attributes of a control applications set the ``id`` field
of a struct :ref:`v4l2_queryctrl <v4l2-queryctrl>` and call the
``VIDIOC_QUERYCTRL`` ioctl with a pointer to this structure. The driver
-fills the rest of the structure or returns an EINVAL error code when the
+fills the rest of the structure or returns an ``EINVAL`` error code when the
``id`` is invalid.
It is possible to enumerate controls by calling ``VIDIOC_QUERYCTRL``
with successive ``id`` values starting from ``V4L2_CID_BASE`` up to and
-exclusive ``V4L2_CID_LASTP1``. Drivers may return EINVAL if a control in
+exclusive ``V4L2_CID_LASTP1``. Drivers may return ``EINVAL`` if a control in
this range is not supported. Further applications can enumerate private
controls, which are not defined in this specification, by starting at
``V4L2_CID_PRIVATE_BASE`` and incrementing ``id`` until the driver
-returns EINVAL.
+returns ``EINVAL``.
In both cases, when the driver sets the ``V4L2_CTRL_FLAG_DISABLED`` flag
in the ``flags`` field this control is permanently disabled and should
be ignored by the application. [1]_
When the application ORs ``id`` with ``V4L2_CTRL_FLAG_NEXT_CTRL`` the
-driver returns the next supported non-compound control, or EINVAL if
+driver returns the next supported non-compound control, or ``EINVAL`` if
there is none. In addition, the ``V4L2_CTRL_FLAG_NEXT_COMPOUND`` flag
can be specified to enumerate all compound controls (i.e. controls with
type ≥ ``V4L2_CTRL_COMPOUND_TYPES`` and/or array control, in other words
controls that contain more than one value). Specify both
``V4L2_CTRL_FLAG_NEXT_CTRL`` and ``V4L2_CTRL_FLAG_NEXT_COMPOUND`` in
order to enumerate all controls, compound or not. Drivers which do not
-support these flags yet always return EINVAL.
+support these flags yet always return ``EINVAL``.
The ``VIDIOC_QUERY_EXT_CTRL`` ioctl was introduced in order to better
support controls that can use compound types, and to expose additional
menu items. To query them applications set the ``id`` and ``index``
fields of struct :ref:`v4l2_querymenu <v4l2-querymenu>` and call the
``VIDIOC_QUERYMENU`` ioctl with a pointer to this structure. The driver
-fills the rest of the structure or returns an EINVAL error code when the
+fills the rest of the structure or returns an ``EINVAL`` error code when the
``id`` or ``index`` is invalid. Menu items are enumerated by calling
``VIDIOC_QUERYMENU`` with successive ``index`` values from struct
:ref:`v4l2_queryctrl <v4l2-queryctrl>` ``minimum`` to ``maximum``,
inclusive. Note that it is possible for ``VIDIOC_QUERYMENU`` to return
-an EINVAL error code for some indices between ``minimum`` and
+an ``EINVAL`` error code for some indices between ``minimum`` and
``maximum``. In that case that particular menu item is not supported by
this driver. Also note that the ``minimum`` value is not necessarily 0.
:ref:`control-id` for predefined IDs. When the ID is ORed with
V4L2_CTRL_FLAG_NEXT_CTRL the driver clears the flag and
returns the first control with a higher ID. Drivers which do not
- support this flag yet always return an EINVAL error code.
+ support this flag yet always return an ``EINVAL`` error code.
- .. row 2
- 0
- A control which performs an action when set. Drivers must ignore
- the value passed with ``VIDIOC_S_CTRL`` and return an EINVAL error
+ the value passed with ``VIDIOC_S_CTRL`` and return an ``EINVAL`` error
code on a ``VIDIOC_G_CTRL`` attempt.
- .. row 8
control ID equal to a control class code (see :ref:`ctrl-class`)
+ 1, the ioctl returns the name of the control class and this
control type. Older drivers which do not support this feature
- return an EINVAL error code.
+ return an ``EINVAL`` error code.
- .. row 11
- This control is permanently disabled and should be ignored by the
application. Any attempt to change the control will result in an
- EINVAL error code.
+ ``EINVAL`` error code.
- .. row 2
- This control is temporarily unchangeable, for example because
another application took over control of the respective resource.
Such controls may be displayed specially in a user interface.
- Attempts to change the control may result in an EBUSY error code.
+ Attempts to change the control may result in an ``EBUSY`` error code.
- .. row 3
- 0x0004
- This control is permanently readable only. Any attempt to change
- the control will result in an EINVAL error code.
+ the control will result in an ``EINVAL`` error code.
- .. row 4
- 0x0040
- This control is permanently writable only. Any attempt to read the
- control will result in an EACCES error code error code. This flag
+ control will result in an ``EACCES`` error code error code. This flag
is typically present for relative controls or action controls
where writing a value will cause the device to carry out a given
action (e. g. motor control) but no meaningful value can be
.. [1]
``V4L2_CTRL_FLAG_DISABLED`` was intended for two purposes: Drivers
can skip predefined controls not supported by the hardware (although
- returning EINVAL would do as well), or disable predefined and private
+ returning ``EINVAL`` would do as well), or disable predefined and private
controls after hardware detection without the trouble of reordering
- control arrays and indices (EINVAL cannot be used to skip private
+ control arrays and indices (``EINVAL`` cannot be used to skip private
controls because it would prematurely end the enumeration).
function correctly. For example video output requires at least two
buffers, one displayed and one filled by the application.
-When the I/O method is not supported the ioctl returns an EINVAL error
+When the I/O method is not supported the ioctl returns an ``EINVAL`` error
code.
Applications can call :ref:`VIDIOC_REQBUFS` again to change the number of
This ioctl is supported if the ``V4L2_CAP_HW_FREQ_SEEK`` capability is
set.
-If this ioctl is called from a non-blocking filehandle, then EAGAIN
+If this ioctl is called from a non-blocking filehandle, then ``EAGAIN``
error code is returned and no seek takes place.
to this structure. Drivers fill the rest of the structure or return an
EINVAL error code if one of the input fields is invalid. All frame
intervals are enumerable by beginning at index zero and incrementing by
-one until EINVAL is returned.
+one until ``EINVAL`` is returned.
Available frame intervals may depend on the current 'try' formats at
other pads of the sub-device, as well as on the current active links.
struct
:ref:`v4l2_subdev_mbus_code_enum <v4l2-subdev-mbus-code-enum>` and
call the :ref:`VIDIOC_SUBDEV_ENUM_MBUS_CODE` ioctl with a pointer to this
-structure. Drivers fill the rest of the structure or return an EINVAL
+structure. Drivers fill the rest of the structure or return an ``EINVAL``
error code if either the ``pad`` or ``index`` are invalid. All media bus
formats are enumerable by beginning at index zero and incrementing by
-one until EINVAL is returned.
+one until ``EINVAL`` is returned.
Available media bus formats may depend on the current 'try' formats at
other pads of the sub-device, as well as on the current active links.
desired pad number as reported by the media API and the ``which`` field
to ``V4L2_SUBDEV_FORMAT_ACTIVE``. They then call the
``VIDIOC_SUBDEV_G_CROP`` ioctl with a pointer to this structure. The
-driver fills the members of the ``rect`` field or returns EINVAL error
+driver fills the members of the ``rect`` field or returns ``EINVAL`` error
code if the input arguments are invalid, or if cropping is not supported
on the given pad.
projects / linux-beck.git / commitdiff
