On 8/4/20 4:29 PM, Helen Koike wrote: > Add documentation and update references in current documentation for the > Extended API. > > Signed-off-by: Helen Koike <helen.koike@xxxxxxxxxxxxx> > --- > Changes in v5: > - new patch > > .../userspace-api/media/v4l/buffer.rst | 5 + > .../userspace-api/media/v4l/common.rst | 1 + > .../userspace-api/media/v4l/dev-capture.rst | 5 + > .../userspace-api/media/v4l/dev-output.rst | 5 + > .../userspace-api/media/v4l/ext-api.rst | 107 +++++++++ > .../userspace-api/media/v4l/format.rst | 16 +- > .../userspace-api/media/v4l/user-func.rst | 5 + > .../media/v4l/vidioc-ext-create-bufs.rst | 95 ++++++++ > .../media/v4l/vidioc-ext-prepare-buf.rst | 62 ++++++ > .../media/v4l/vidioc-ext-qbuf.rst | 204 ++++++++++++++++++ > .../media/v4l/vidioc-ext-querybuf.rst | 79 +++++++ > .../media/v4l/vidioc-g-ext-pix-fmt.rst | 117 ++++++++++ > 12 files changed, 697 insertions(+), 4 deletions(-) > create mode 100644 Documentation/userspace-api/media/v4l/ext-api.rst > create mode 100644 Documentation/userspace-api/media/v4l/vidioc-ext-create-bufs.rst > create mode 100644 Documentation/userspace-api/media/v4l/vidioc-ext-prepare-buf.rst > create mode 100644 Documentation/userspace-api/media/v4l/vidioc-ext-qbuf.rst > create mode 100644 Documentation/userspace-api/media/v4l/vidioc-ext-querybuf.rst > create mode 100644 Documentation/userspace-api/media/v4l/vidioc-g-ext-pix-fmt.rst > > diff --git a/Documentation/userspace-api/media/v4l/buffer.rst b/Documentation/userspace-api/media/v4l/buffer.rst > index 57e752aaf414a..c832bedd64e4c 100644 > --- a/Documentation/userspace-api/media/v4l/buffer.rst > +++ b/Documentation/userspace-api/media/v4l/buffer.rst > @@ -27,6 +27,11 @@ such as pointers and sizes for each plane, are stored in > struct :c:type:`v4l2_plane` instead. In that case, > struct :c:type:`v4l2_buffer` contains an array of plane structures. > > +.. note:: > + > + The :ref:`ext_api` version can also be used, and it is > + preferable when applicable. > + > Dequeued video buffers come with timestamps. The driver decides at which > part of the frame and with which clock the timestamp is taken. Please > see flags in the masks ``V4L2_BUF_FLAG_TIMESTAMP_MASK`` and > diff --git a/Documentation/userspace-api/media/v4l/common.rst b/Documentation/userspace-api/media/v4l/common.rst > index 7d81c58a13cd7..3430e0bdad667 100644 > --- a/Documentation/userspace-api/media/v4l/common.rst > +++ b/Documentation/userspace-api/media/v4l/common.rst > @@ -59,6 +59,7 @@ applicable to all devices. > ext-ctrls-detect > fourcc > format > + ext-api > planar-apis > selection-api > crop > diff --git a/Documentation/userspace-api/media/v4l/dev-capture.rst b/Documentation/userspace-api/media/v4l/dev-capture.rst > index 44d3094093ab6..5077639787d92 100644 > --- a/Documentation/userspace-api/media/v4l/dev-capture.rst > +++ b/Documentation/userspace-api/media/v4l/dev-capture.rst > @@ -102,6 +102,11 @@ and :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl, even if :ref:`VIDIOC_S_FMT <VIDIOC > requests and always returns default parameters as :ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>` does. > :ref:`VIDIOC_TRY_FMT <VIDIOC_G_FMT>` is optional. > > +.. note:: > + > + The :ref:`ext_api` version can also be used, and it is > + preferable when applicable. > + > > Reading Images > ============== > diff --git a/Documentation/userspace-api/media/v4l/dev-output.rst b/Documentation/userspace-api/media/v4l/dev-output.rst > index e4f2a1d8b0fc7..f8f40c708e49f 100644 > --- a/Documentation/userspace-api/media/v4l/dev-output.rst > +++ b/Documentation/userspace-api/media/v4l/dev-output.rst > @@ -99,6 +99,11 @@ and :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl, even if :ref:`VIDIOC_S_FMT <VIDIOC > requests and always returns default parameters as :ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>` does. > :ref:`VIDIOC_TRY_FMT <VIDIOC_G_FMT>` is optional. > > +.. note:: > + > + The :ref:`ext_api` version can also be used, and it is > + preferable when applicable. > + > > Writing Images > ============== > diff --git a/Documentation/userspace-api/media/v4l/ext-api.rst b/Documentation/userspace-api/media/v4l/ext-api.rst > new file mode 100644 > index 0000000000000..da2a82960d22f > --- /dev/null > +++ b/Documentation/userspace-api/media/v4l/ext-api.rst > @@ -0,0 +1,107 @@ > +.. Permission is granted to copy, distribute and/or modify this > +.. document under the terms of the GNU Free Documentation License, > +.. Version 1.1 or any later version published by the Free Software > +.. Foundation, with no Invariant Sections, no Front-Cover Texts > +.. and no Back-Cover Texts. A copy of the license is included at > +.. Documentation/userspace-api/media/fdl-appendix.rst. > +.. > +.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections > + > +.. _ext_api: > + > +************* > +Extendend API > +************* > + > +Introduction > +============ > + > +The Extended Format API was conceived to extend V4L2 capabilities and > +to simplify certain mechanisms. > +It unifies single- vs multi- planar handling, > +brings the concept of pixelformat + modifiers, allows planes to be placed > +in any offset inside a buffer and let userspace to change colorspace > +attributes if supported by the driver. > + > +Data format negotiation and buffer handling works very similar to the classical > +version, thus in this document we'll just mention the main differences. > + > +Data Format Negotiation > +======================= > + > +The API replaces the classical ioctls: > + > +:ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>`, :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>`, > +:ref:`VIDIOC_TRY_FMT <VIDIOC_G_FMT>` > +(with :c:type:`v4l2_format` as the main parameter). > + > +By the extended versions: > + > +:ref:`VIDIOC_G_EXT_PIX_FMT <VIDIOC_G_EXT_PIX_FMT>`, > +:ref:`VIDIOC_S_EXT_PIX_FMT <VIDIOC_G_EXT_PIX_FMT>`, > +:ref:`VIDIOC_TRY_EXT_PIX_FMT <VIDIOC_G_EXT_PIX_FMT>` > +(with :c:type:`v4l2_ext_pix_format` as the main parameter). > + > +For CAPTURE and OUTPUT queues only. > + > +The ``type`` field of struct :c:type:`v4l2_ext_pix_format` only accepts > +``V4L2_BUF_TYPE_VIDEO_CAPTURE`` or ``V4L2_BUF_TYPE_VIDEO_OUTPUT``, and it > +supports multiplanar format through a combination of ``pixelfomat`` and > +``modifier`` fields. > + > +Only the single-planar variants of the pixel formats are valid in the > +``pixelformat`` field. Just a correction, here I meant s/single-planar/non-M-variant. But this is under discussion, see patch 1/7. > +To support multi-planar, a modifier should be set in the ``modifier`` field to > +provide more information regarding the memory layout of pixels and number of > +planes. This is wrong too. Or we don't use the M-variant, or we say both variants are valid and equivalent. This is under discussion, see patch 1/7. I'll update in the next version. Regards, Helen > + > +The ``plane_fmt`` field is an array which holds information by plane using > +the :c:type:`v4l2_plane_ext_pix_format`. When this struct is filled, its > +``sizeimage`` field should be non-zero for all valid planes for a given > +``pixelformat`` + ``modifier`` combination, and zeroed for the invalid ones. > + > +Colospace attributes are not read-only as in the classical version, i.e, they > +can be set by application and drivers will adjust accordingly depending on what > +is supported by the underlying hardware. > + > +Buffers > +======= > + > +The API replaces the classical ioctls: > + > +:ref:`VIDIOC_CREATE_BUFS <VIDIOC_CREATE_BUFS>` > +(with :c:type:`v4l2_create_buffers` as the main parameter), > +:ref:`VIDIOC_QUERYBUF <VIDIOC_QUERYBUF>`, :ref:`VIDIOC_QBUF <VIDIOC_QBUF>`, > +:ref:`VIDIOC_DQBUF <VIDIOC_QBUF>`, :ref:`VIDIOC_PREPARE_BUF <VIDIOC_PREPARE_BUF>` > +(with :c:type:`v4l2_buffer` as the main parameter) > + > +By the extended versions: > + > +:ref:`VIDIOC_EXT_CREATE_BUFS <VIDIOC_EXT_CREATE_BUFS>` > +(with :c:type:`v4l2_ext_create_buffers` as the main parameter), > +:ref:`VIDIOC_EXT_QUERYBUF <VIDIOC_EXT_QUERYBUF>`, > +:ref:`VIDIOC_EXT_QBUF <VIDIOC_EXT_QBUF>`, > +:ref:`VIDIOC_EXT_DQBUF <VIDIOC_EXT_QBUF>`, > +:ref:`VIDIOC_EXT_PREPARE_BUF <VIDIOC_EXT_PREPARE_BUF>` > +(with :c:type:`v4l2_ext_buffer` as the main parameter) > + > +The basic difference between :c:type:`v4l2_create_buffers` and > +:c:type:`v4l2_ext_create_buffers` is that the later have a > +:c:type:`v4l2_ext_pix_format` as the type of the ``format`` field. > + > +Comparing :c:type:`v4l2_ext_buffer` with :c:type:`v4l2_buffer`, in the > +extended version there is a unification of the single-/multi- planar handling > +through the ``planes`` field of type :c:type:`v4l2_ext_plane`. > + > +The :c:type:`v4l2_ext_plane also allows planes to be placed in a given offset > +inside a buffer. > +Planes can be placed in different locations inside the same buffer, or in > +different buffers. > + > + > +.. kernel-doc:: include/uapi/linux/videodev2.h > + :functions: v4l2_ext_plane > + > + > +.. kernel-doc:: include/uapi/linux/videodev2.h > + :functions: v4l2_ext_buffer > diff --git a/Documentation/userspace-api/media/v4l/format.rst b/Documentation/userspace-api/media/v4l/format.rst > index e47fc0505727c..b96d26f26793c 100644 > --- a/Documentation/userspace-api/media/v4l/format.rst > +++ b/Documentation/userspace-api/media/v4l/format.rst > @@ -28,13 +28,19 @@ format and the driver selects and reports the best the hardware can do > to satisfy the request. Of course applications can also just query the > current selection. > > -A single mechanism exists to negotiate all data formats using the > -aggregate struct :c:type:`v4l2_format` and the > +There are two mechanism to negociate data formats: > + > +The first one is using the aggregate struct :c:type:`v4l2_format` and the > :ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>` and > :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctls. Additionally the > :ref:`VIDIOC_TRY_FMT <VIDIOC_G_FMT>` ioctl can be used to examine > what the hardware *could* do, without actually selecting a new data > -format. The data formats supported by the V4L2 API are covered in the > +format. > + > +The second is through the :ref:`ext_api`, please refer to its documentation > +for more information. > + > +The data formats supported by the V4L2 API are covered in the > respective device section in :ref:`devices`. For a closer look at > image formats see :ref:`pixfmt`. > > @@ -71,7 +77,9 @@ earlier versions of V4L2. Switching the logical stream or returning into > *may* support a switch using :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>`. > > All drivers exchanging data with applications must support the > -:ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>` and :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl. Implementation of the > +:ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>` and :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl > +or the Extended respective versions (TODO: link). > +Implementation of the > :ref:`VIDIOC_TRY_FMT <VIDIOC_G_FMT>` is highly recommended but optional. > > > diff --git a/Documentation/userspace-api/media/v4l/user-func.rst b/Documentation/userspace-api/media/v4l/user-func.rst > index bf77c842718e5..67b254812791c 100644 > --- a/Documentation/userspace-api/media/v4l/user-func.rst > +++ b/Documentation/userspace-api/media/v4l/user-func.rst > @@ -20,6 +20,7 @@ Function Reference > func-close > func-ioctl > vidioc-create-bufs > + vidioc-ext-create-bufs > vidioc-cropcap > vidioc-dbg-g-chip-info > vidioc-dbg-g-register > @@ -48,6 +49,7 @@ Function Reference > vidioc-g-ext-ctrls > vidioc-g-fbuf > vidioc-g-fmt > + vidioc-g-ext-pix-fmt > vidioc-g-frequency > vidioc-g-input > vidioc-g-jpegcomp > @@ -62,8 +64,11 @@ Function Reference > vidioc-log-status > vidioc-overlay > vidioc-prepare-buf > + vidioc-ext-prepare-buf > vidioc-qbuf > + vidioc-ext-qbuf > vidioc-querybuf > + vidioc-ext-querybuf > vidioc-querycap > vidioc-queryctrl > vidioc-query-dv-timings > diff --git a/Documentation/userspace-api/media/v4l/vidioc-ext-create-bufs.rst b/Documentation/userspace-api/media/v4l/vidioc-ext-create-bufs.rst > new file mode 100644 > index 0000000000000..67f2c541e4d79 > --- /dev/null > +++ b/Documentation/userspace-api/media/v4l/vidioc-ext-create-bufs.rst > @@ -0,0 +1,95 @@ > +.. Permission is granted to copy, distribute and/or modify this > +.. document under the terms of the GNU Free Documentation License, > +.. Version 1.1 or any later version published by the Free Software > +.. Foundation, with no Invariant Sections, no Front-Cover Texts > +.. and no Back-Cover Texts. A copy of the license is included at > +.. Documentation/userspace-api/media/fdl-appendix.rst. > +.. > +.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections > + > +.. _VIDIOC_EXT_CREATE_BUFS: > + > +**************************** > +ioctl VIDIOC_EXT_CREATE_BUFS > +**************************** > + > +Name > +==== > + > +VIDIOC_EXT_CREATE_BUFS - Create buffers for Memory Mapped or User Pointer or DMA Buffer I/O > + > + > +Synopsis > +======== > + > +.. c:function:: int ioctl( int fd, VIDIOC_EXT_CREATE_BUFS, struct v4l2_ext_create_buffers *argp ) > + :name: VIDIOC_EXT_CREATE_BUFS > + > + > +Arguments > +========= > + > +``fd`` > + File descriptor returned by :ref:`open() <func-open>`. > + > +``argp`` > + Pointer to struct :c:type:`v4l2_ext_create_buffers`. > + > + > +Description > +=========== > + > +This ioctl is used to create buffers for :ref:`memory mapped <mmap>` > +or :ref:`user pointer <userp>` or :ref:`DMA buffer <dmabuf>` I/O. > +This ioctl can be called multiple times to > +create buffers of different sizes. > + > +To allocate the device buffers applications must initialize the relevant > +fields of the struct :c:type:`v4l2_ext_create_buffers` structure. The > +``count`` field must be set to the number of requested buffers, the > +``memory`` field specifies the requested I/O method and the ``reserved`` > +array must be zeroed. > + > +The ``format`` field specifies the image format that the buffers must be > +able to handle. The application has to fill in this struct > +:c:type:`v4l2_format`. Usually this will be done using the > +:ref:`VIDIOC_TRY_EXT_PIX_FMT <VIDIOC_G_EXT_PIX_FMT>` or > +:ref:`VIDIOC_G_EXT_PIX_FMT <VIDIOC_G_EXT_PIX_FMT>` ioctls to ensure that the > +requested format is supported by the driver. > +The driver may return an error if the size(s) are not supported by the > +hardware (usually because they are too small). > + > +The driver can create a memory buffer per plane, or a single memory buffer > +containing all the planes, with a minimum size according to the size > +defined by the ``format.plane_fmt[i].sizeimage`` field. > +Usually if the ``format.plane_fmt[i].sizeimage`` > +field is less than the minimum required for the given format, then an > +error will be returned since drivers will typically not allow this. If > +it is larger, then the value will be used as-is. In other words, the > +driver may reject the requested size, but if it is accepted the driver > +will use it unchanged. > + > +When the ioctl is called with a pointer to this structure the driver > +will attempt to allocate up to the requested number of buffers and store > +the actual number allocated and the starting index in the ``count`` and > +the ``index`` fields respectively. On return ``count`` can be smaller > +than the number requested. > + > + > +.. kernel-doc:: include/uapi/linux/videodev2.h > + :functions: v4l2_ext_create_buffers > + > + > +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. > + > +ENOMEM > + No memory to allocate buffers for :ref:`memory mapped <mmap>` I/O. > + > +EINVAL > + The buffer type (``format.type`` field), requested I/O method > + (``memory``) or format (``format`` field) is not valid. > diff --git a/Documentation/userspace-api/media/v4l/vidioc-ext-prepare-buf.rst b/Documentation/userspace-api/media/v4l/vidioc-ext-prepare-buf.rst > new file mode 100644 > index 0000000000000..88e4b57121254 > --- /dev/null > +++ b/Documentation/userspace-api/media/v4l/vidioc-ext-prepare-buf.rst > @@ -0,0 +1,62 @@ > +.. Permission is granted to copy, distribute and/or modify this > +.. document under the terms of the GNU Free Documentation License, > +.. Version 1.1 or any later version published by the Free Software > +.. Foundation, with no Invariant Sections, no Front-Cover Texts > +.. and no Back-Cover Texts. A copy of the license is included at > +.. Documentation/userspace-api/media/fdl-appendix.rst. > +.. > +.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections > + > +.. _VIDIOC_EXT_PREPARE_BUF: > + > +**************************** > +ioctl VIDIOC_EXT_PREPARE_BUF > +**************************** > + > +Name > +==== > + > +VIDIOC_EXT_PREPARE_BUF - Prepare a buffer for I/O > + > + > +Synopsis > +======== > + > +.. c:function:: int ioctl( int fd, VIDIOC_EXT_PREPARE_BUF, struct v4l2_ext_buffer *argp ) > + :name: VIDIOC_EXT_PREPARE_BUF > + > + > +Arguments > +========= > + > +``fd`` > + File descriptor returned by :ref:`open() <func-open>`. > + > +``argp`` > + Pointer to struct :c:type:`v4l2_ext_buffer`. > + > + > +Description > +=========== > + > +Applications can optionally call the :ref:`VIDIOC_EXT_PREPARE_BUF` ioctl to > +pass ownership of the buffer to the driver before actually enqueuing it, > +using the :ref:`VIDIOC_EXT_QBUF <VIDIOC_EXT_QBUF>` ioctl, and to prepare it for future I/O. Such > +preparations may include cache invalidation or cleaning. Performing them > +in advance saves time during the actual I/O. > + > + > +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 > + File I/O is in progress. > + > +EINVAL > + The buffer ``type`` is not supported, or the ``index`` is out of > + bounds, or no buffers have been allocated yet, or the ``userptr`` or > + ``length`` are invalid. > diff --git a/Documentation/userspace-api/media/v4l/vidioc-ext-qbuf.rst b/Documentation/userspace-api/media/v4l/vidioc-ext-qbuf.rst > new file mode 100644 > index 0000000000000..083e106cf6bad > --- /dev/null > +++ b/Documentation/userspace-api/media/v4l/vidioc-ext-qbuf.rst > @@ -0,0 +1,204 @@ > +.. Permission is granted to copy, distribute and/or modify this > +.. document under the terms of the GNU Free Documentation License, > +.. Version 1.1 or any later version published by the Free Software > +.. Foundation, with no Invariant Sections, no Front-Cover Texts > +.. and no Back-Cover Texts. A copy of the license is included at > +.. Documentation/userspace-api/media/fdl-appendix.rst. > +.. > +.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections > + > +.. _VIDIOC_EXT_QBUF: > + > +*************************************** > +ioctl VIDIOC_EXT_QBUF, VIDIOC_EXT_DQBUF > +*************************************** > + > +Name > +==== > + > +VIDIOC_EXT_QBUF - VIDIOC_EXT_DQBUF - Exchange a buffer with the driver > + > + > +Synopsis > +======== > + > +.. c:function:: int ioctl( int fd, VIDIOC_EXT_QBUF, struct v4l2_ext_buffer *argp ) > + :name: VIDIOC_EXT_QBUF > + > +.. c:function:: int ioctl( int fd, VIDIOC_EXT_DQBUF, struct v4l2_ext_buffer *argp ) > + :name: VIDIOC_EXT_DQBUF > + > + > +Arguments > +========= > + > +``fd`` > + File descriptor returned by :ref:`open() <func-open>`. > + > +``argp`` > + Pointer to struct :c:type:`v4l2_ext_buffer`. > + > + > +Description > +=========== > + > +Applications call the ``VIDIOC_EXT_QBUF`` ioctl to enqueue an empty > +(capturing) or filled (output) buffer in the driver's incoming queue. > +The semantics depend on the selected I/O method. > + > +To enqueue a buffer applications set the ``type`` field of a struct > +:c:type:`v4l2_ext_buffer` to the same buffer type as was > +previously used with struct :c:type:`v4l2_ext_pix_format` ``type``. > +Applications must also set the ``index`` field. Valid index numbers > +range from zero to the number of buffers allocated with > +:ref:`VIDIOC_EXT_CREATE_BUFS` (struct > +:c:type:`v4l2_ext_create_buffers` ``count``) minus > +one. The contents of the struct :c:type:`v4l2_ext_buffer` returned > +by a :ref:`VIDIOC_EXT_QUERYBUF` ioctl will do as well. > +When the buffer is intended for output (``type`` is > +``V4L2_BUF_TYPE_VIDEO_OUTPUT``) applications must also initialize the > +``timestamp`` fields and the ``planes[i].plane_length`` for each valid plane, > +and invalid ones must be set as zero. > +see :ref:`buffer` for details. Applications must also set ``flags`` to 0. The > +``reserved`` field must be set to 0. > + > +To enqueue a :ref:`memory mapped <mmap>` buffer applications set the > +``planes[i].memory`` field to ``V4L2_MEMORY_MMAP`` in all the valid planes, > +and invalid ones must be set as zero. > +When ``VIDIOC_EXT_QBUF`` is called > +with a pointer to this structure the driver sets the > +``V4L2_BUF_FLAG_MAPPED`` and ``V4L2_BUF_FLAG_QUEUED`` flags and clears > +the ``V4L2_BUF_FLAG_DONE`` flag in the ``flags`` field, or it returns an > +``EINVAL`` error code. > + > +To enqueue a :ref:`user pointer <userp>` buffer applications set the > +``planes[i].memory`` field to ``V4L2_MEMORY_USERPTR`` in all the valid planes, > +and invalid ones must be set as zero, the ``planes[i].m.userptr`` field to the > +address of the buffer,``planes[i].buffer_length`` to the size of the memory > +buffer, ``planes[i].plane_length`` to the size that should be used by the plane, > +and ``planes[i].offset`` of the plane in the memory buffer. > + > +When ``VIDIOC_EXT_QBUF`` is called with a pointer to this structure > +the driver sets the ``V4L2_BUF_FLAG_QUEUED`` flag and clears the > +``V4L2_BUF_FLAG_MAPPED`` and ``V4L2_BUF_FLAG_DONE`` flags in the > +``flags`` field, or it returns an error code. This ioctl locks the > +memory pages of the buffer in physical memory, they cannot be swapped > +out to disk. Buffers remain locked until dequeued, until the > +:ref:`VIDIOC_STREAMOFF <VIDIOC_STREAMON>` or > +:ref:`VIDIOC_EXT_CREATE_BUFS` ioctl is called, or until the > +device is closed. > + > +To enqueue a :ref:`DMABUF <dmabuf>` buffer applications set the > +``planes[i].memory`` field to ``V4L2_MEMORY_DMABUF`` in all the valid planes, > +and invalid ones must be set as zero, the ``planes[i].m.fd`` field to a > +file descriptor associated with a DMABUF buffer.,``planes[i].buffer_length`` to > +the size of the memory buffer, ``planes[i].plane_length`` to the size that > +should be used by the plane, and ``planes[i].offset`` of the plane in the memory buffer. > +When ``VIDIOC_EXT_QBUF`` is called with a pointer to this structure the driver > +sets the ``V4L2_BUF_FLAG_QUEUED`` flag and clears the > +``V4L2_BUF_FLAG_MAPPED`` and ``V4L2_BUF_FLAG_DONE`` flags in the > +``flags`` field, or it returns an error code. This ioctl locks the > +buffer. Locking a buffer means passing it to a driver for a hardware > +access (usually DMA). If an application accesses (reads/writes) a locked > +buffer then the result is undefined. Buffers remain locked until > +dequeued, until the :ref:`VIDIOC_STREAMOFF <VIDIOC_STREAMON>` or > +:ref:`VIDIOC_EXT_CREATE_BUFS` ioctl is called, or until the > +device is closed. > + > +The ``request_fd`` field can be used with the ``VIDIOC_EXT_QBUF`` ioctl to specify > +the file descriptor of a :ref:`request <media-request-api>`, if requests are > +in use. Setting it means that the buffer will not be passed to the driver > +until the request itself is queued. Also, the driver will apply any > +settings associated with the request for this buffer. This field will > +be ignored unless the ``V4L2_BUF_FLAG_REQUEST_FD`` flag is set. > +If the device does not support requests, then ``EBADR`` will be returned. > +If requests are supported but an invalid request file descriptor is given, > +then ``EINVAL`` will be returned. > + > +.. caution:: > + It is not allowed to mix queuing requests with queuing buffers directly. > + ``EBUSY`` will be returned if the first buffer was queued directly and > + then the application tries to queue a request, or vice versa. After > + closing the file descriptor, calling > + :ref:`VIDIOC_STREAMOFF <VIDIOC_STREAMON>` or calling :ref:`VIDIOC_EXT_CREATE_BUFS` > + the check for this will be reset. > + > + For :ref:`memory-to-memory devices <mem2mem>` you can specify the > + ``request_fd`` only for output buffers, not for capture buffers. Attempting > + to specify this for a capture buffer will result in an ``EBADR`` error. > + > +Applications call the ``VIDIOC_EXT_DQBUF`` ioctl to dequeue a filled > +(capturing) or displayed (output) buffer from the driver's outgoing > +queue. They just set the ``type``, ``planes[i].memory`` and ``reserved`` fields of > +a struct :c:type:`v4l2_ext_buffer` as above, when > +``VIDIOC_EXT_DQBUF`` is called with a pointer to this structure the driver > +fills the remaining fields or returns an error code. The driver may also > +set ``V4L2_BUF_FLAG_ERROR`` in the ``flags`` field. It indicates a > +non-critical (recoverable) streaming error. In such case the application > +may continue as normal, but should be aware that data in the dequeued > +buffer might be corrupted. When using the multi-planar API, the planes > +array must be passed in as well. > + > +If the application sets the ``memory`` field to ``V4L2_MEMORY_DMABUF`` to > +dequeue a :ref:`DMABUF <dmabuf>` buffer, the driver fills the ``m.fd`` field > +with a file descriptor numerically the same as the one given to ``VIDIOC_EXT_QBUF`` > +when the buffer was enqueued. No new file descriptor is created at dequeue time > +and the value is only for the application convenience. > + > +By default ``VIDIOC_EXT_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_EXT_DQBUF`` returns > +immediately with an ``EAGAIN`` error code when no buffer is available. > + > + > +.. kernel-doc:: include/uapi/linux/videodev2.h > + :functions: v4l2_ext_buffers > + > + > +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. > + > +EAGAIN > + Non-blocking I/O has been selected using ``O_NONBLOCK`` and no > + buffer was in the outgoing queue. > + > +EINVAL > + The buffer ``type`` is not supported, or the ``index`` is out of > + bounds, or no buffers have been allocated yet, or the ``userptr`` or > + ``length`` are invalid, or the ``V4L2_BUF_FLAG_REQUEST_FD`` flag was > + set but the the given ``request_fd`` was invalid, or ``m.fd`` was > + an invalid DMABUF file descriptor. > + > +EIO > + ``VIDIOC_EXT_DQBUF`` failed due to an internal error. Can also indicate > + temporary problems like signal loss. > + > + .. note:: > + > + The driver might dequeue an (empty) buffer despite returning > + an error, or even stop capturing. Reusing such buffer may be unsafe > + though and its details (e.g. ``index``) may not be returned either. > + It is recommended that drivers indicate recoverable errors by setting > + the ``V4L2_BUF_FLAG_ERROR`` and returning 0 instead. In that case the > + application should be able to safely reuse the buffer and continue > + streaming. > + > +EPIPE > + ``VIDIOC_EXT_DQBUF`` returns this on an empty capture queue for mem2mem > + codecs if a buffer with the ``V4L2_BUF_FLAG_LAST`` was already > + dequeued and no new buffers are expected to become available. > + > +EBADR > + The ``V4L2_BUF_FLAG_REQUEST_FD`` flag was set but the device does not > + support requests for the given buffer type, or > + the ``V4L2_BUF_FLAG_REQUEST_FD`` flag was not set but the device requires > + that the buffer is part of a request. > + > +EBUSY > + The first buffer was queued via a request, but the application now tries > + to queue it directly, or vice versa (it is not permitted to mix the two > + APIs). > diff --git a/Documentation/userspace-api/media/v4l/vidioc-ext-querybuf.rst b/Documentation/userspace-api/media/v4l/vidioc-ext-querybuf.rst > new file mode 100644 > index 0000000000000..f2a12017253f6 > --- /dev/null > +++ b/Documentation/userspace-api/media/v4l/vidioc-ext-querybuf.rst > @@ -0,0 +1,79 @@ > +.. Permission is granted to copy, distribute and/or modify this > +.. document under the terms of the GNU Free Documentation License, > +.. Version 1.1 or any later version published by the Free Software > +.. Foundation, with no Invariant Sections, no Front-Cover Texts > +.. and no Back-Cover Texts. A copy of the license is included at > +.. Documentation/userspace-api/media/fdl-appendix.rst. > +.. > +.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections > + > +.. _VIDIOC_EXT_QUERYBUF: > + > +************************* > +ioctl VIDIOC_EXT_QUERYBUF > +************************* > + > +Name > +==== > + > +VIDIOC_EXT_QUERYBUF - Query the status of a buffer > + > + > +Synopsis > +======== > + > +.. c:function:: int ioctl( int fd, VIDIOC_EXT_QUERYBUF, struct v4l2_ext_buffer *argp ) > + :name: VIDIOC_EXT_QUERYBUF > + > + > +Arguments > +========= > + > +``fd`` > + File descriptor returned by :ref:`open() <func-open>`. > + > +``argp`` > + Pointer to struct :c:type:`v4l2_ext_buffer`. > + > + > +Description > +=========== > + > +This ioctl is part of the :ref:`streaming <mmap>` I/O method. It can > +be used to query the status of a buffer at any time after buffers have > +been allocated with the :ref:`VIDIOC_EXT_CREATE_BUFS` ioctl. > + > +Applications set the ``type`` field of a struct > +:c:type:`v4l2_ext_buffer` to the same buffer type as was > +previously used with struct :c:type:`v4l2_ext_pix_format` ``type``, > +and the ``index`` field. Valid index numbers range from zero to the > +number of buffers allocated with > +:ref:`VIDIOC_EXT_CREATE_BUFS` (struct > +:c:type:`v4l2_ext_create_buffers` ``count``) minus > +one. The ``reserved`` field must be set to 0. > + > +In the ``flags`` field the ``V4L2_BUF_FLAG_MAPPED``, > +``V4L2_BUF_FLAG_PREPARED``, ``V4L2_BUF_FLAG_QUEUED`` and > +``V4L2_BUF_FLAG_DONE`` flags will be valid. The ``planes.memory`` fields will be > +set to the current I/O method for each plane. > + > +For every valid plane, an entry in ``planes`` will be filled, and zeroed for > +invalid ones. ``planes[i].buffer_length`` is the size of the memory buffer > +which contains the plane, ``planes[i].plane_length`` is the length of the plane, > +and ``planes[i].offset` is where the plane is placed in the memory buffer. > + > +The size of the ``planes`` array can be calculated by the number of sequential > +planes with ``planes[i].buffer_length`` that differs from zero up to the max > +size of the array. > + > + > +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. > + > +EINVAL > + The buffer ``type`` is not supported, or the ``index`` is out of > + bounds. > diff --git a/Documentation/userspace-api/media/v4l/vidioc-g-ext-pix-fmt.rst b/Documentation/userspace-api/media/v4l/vidioc-g-ext-pix-fmt.rst > new file mode 100644 > index 0000000000000..008e6c98a88a5 > --- /dev/null > +++ b/Documentation/userspace-api/media/v4l/vidioc-g-ext-pix-fmt.rst > @@ -0,0 +1,117 @@ > +.. Permission is granted to copy, distribute and/or modify this > +.. document under the terms of the GNU Free Documentation License, > +.. Version 1.1 or any later version published by the Free Software > +.. Foundation, with no Invariant Sections, no Front-Cover Texts > +.. and no Back-Cover Texts. A copy of the license is included at > +.. Documentation/userspace-api/media/fdl-appendix.rst. > +.. > +.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections > + > +.. _VIDIOC_G_EXT_PIX_FMT: > + > +************************************************************************ > +ioctl VIDIOC_G_EXT_PIX_FMT, VIDIOC_S_EXT_PIX_FMT, VIDIOC_TRY_EXT_PIX_FMT > +************************************************************************ > + > +Name > +==== > + > +VIDIOC_G_EXT_PIX_FMT - VIDIOC_S_EXT_PIX_FMT - VIDIOC_TRY_EXT_PIX_FMT - Get or set the data format, try a format > + > + > +Synopsis > +======== > + > +.. c:function:: int ioctl( int fd, VIDIOC_G_EXT_PIX_FMT, struct v4l2_ext_pix_format *argp ) > + :name: VIDIOC_G_EXT_PIX_FMT > + > +.. c:function:: int ioctl( int fd, VIDIOC_S_EXT_PIX_FMT, struct v4l2_ext_pix_format *argp ) > + :name: VIDIOC_S_EXT_PIX_FMT > + > +.. c:function:: int ioctl( int fd, VIDIOC_TRY_EXT_PIX_FMT, struct v4l2_ext_pix_format *argp ) > + :name: VIDIOC_TRY_EXT_PIX_FMT > + > +Arguments > +========= > + > +``fd`` > + File descriptor returned by :ref:`open() <func-open>`. > + > +``argp`` > + Pointer to struct :c:type:`v4l2_ext_pix_format`. > + > + > +Description > +=========== > + > +These ioctls are used to negotiate the format of data (typically image > +format) exchanged between driver and application. > + > +To query the current parameters applications set the ``type`` field of a > +struct :c:type:`v4l2_ext_pix_format` to ``V4L2_BUF_TYPE_VIDEO_CAPTURE`` or > +``V4L2_BUF_TYPE_VIDEO_OUTPUT``, all the other types are invalid in this API, > +and multiplanar is supported through modifiers. > + > +When the application calls the > +:ref:`VIDIOC_G_EXT_PIX_FMT <VIDIOC_G_EXT_PIX_FMT>` ioctl with a pointer to this > +structure the driver fills the other members. > +When the requested buffer type is not supported drivers return > +an ``EINVAL`` error code. > + > +To change the current format parameters applications initialize all > +the fields in the struct. > +For details see the documentation of the various devices types in > +:ref:`devices`. Good practice is to query the current parameters > +first, and to modify only those parameters not suitable for the > +application. When the application calls the :ref:`VIDIOC_S_EXT_PIX_FMT <VIDIOC_G_EXT_PIX_FMT>` ioctl with > +a pointer to a struct :c:type:`v4l2_ext_pix_format` structure the driver > +checks and adjusts the parameters against hardware abilities. Drivers > +should not return an error code unless the ``type`` field is invalid, > +this is a mechanism to fathom device capabilities and to approach > +parameters acceptable for both the application and driver. On success > +the driver may program the hardware, allocate resources and generally > +prepare for data exchange. Finally the :ref:`VIDIOC_S_EXT_PIX_FMT <VIDIOC_G_EXT_PIX_FMT>` ioctl returns > +the current format parameters as :ref:`VIDIOC_G_EXT_PIX_FMT <VIDIOC_G_EXT_PIX_FMT>` does. Very simple, > +inflexible devices may even ignore all input and always return the > +default parameters. However all V4L2 devices exchanging data with the > +application must implement the :ref:`VIDIOC_G_EXT_PIX_FMT <VIDIOC_G_EXT_PIX_FMT>` and :ref:`VIDIOC_S_EXT_PIX_FMT <VIDIOC_G_EXT_PIX_FMT>` > +ioctl. When the requested buffer type is not supported drivers return an > +EINVAL error code on a :ref:`VIDIOC_S_EXT_PIX_FMT <VIDIOC_G_EXT_PIX_FMT>` attempt. When I/O is already in > +progress or the resource is not available for other reasons drivers > +return the ``EBUSY`` error code. > + > +The :ref:`VIDIOC_TRY_EXT_PIX_FMT <VIDIOC_G_EXT_PIX_FMT>` ioctl is equivalent to :ref:`VIDIOC_S_EXT_PIX_FMT <VIDIOC_G_EXT_PIX_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 > +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. > + > +The format as returned by :ref:`VIDIOC_TRY_EXT_PIX_FMT <VIDIOC_G_EXT_PIX_FMT>` must be identical to what > +:ref:`VIDIOC_S_EXT_PIX_FMT <VIDIOC_G_EXT_PIX_FMT>` returns for the same input or output. > + > + > +.. kernel-doc:: include/uapi/linux/videodev2.h > + :functions: v4l2_plane_ext_pix_format > + > + > +.. kernel-doc:: include/uapi/linux/videodev2.h > + :functions: v4l2_ext_pix_format > + > + > +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. > + > +EINVAL > + The struct :c:type:`v4l2_ext_pix_format` ``type`` field is > + invalid or the requested buffer type not supported. > + > +EBUSY > + The device is busy and cannot change the format. This could be > + because or the device is streaming or buffers are allocated or > + queued to the driver. Relevant for :ref:`VIDIOC_S_EXT_PIX_FMT > + <VIDIOC_G_EXT_PIX_FMT>` only. >
