diff options
Diffstat (limited to 'Documentation/media/uapi/v4l/vidioc-reqbufs.rst')
| -rw-r--r-- | Documentation/media/uapi/v4l/vidioc-reqbufs.rst | 68 |
1 files changed, 63 insertions, 5 deletions
diff --git a/Documentation/media/uapi/v4l/vidioc-reqbufs.rst b/Documentation/media/uapi/v4l/vidioc-reqbufs.rst index 316f52c8a310..d7faef10e39b 100644 --- a/Documentation/media/uapi/v4l/vidioc-reqbufs.rst +++ b/Documentation/media/uapi/v4l/vidioc-reqbufs.rst @@ -1,4 +1,11 @@ -.. -*- coding: utf-8; mode: rst -*- +.. 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/media/uapi/fdl-appendix.rst. +.. +.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections .. _VIDIOC_REQBUFS: @@ -59,9 +66,14 @@ 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 -buffers, however this cannot succeed when any buffers are still mapped. -A ``count`` value of zero frees all buffers, after aborting or finishing -any DMA in progress, an implicit +buffers. Note that if any buffers are still mapped or exported via DMABUF, +then :ref:`VIDIOC_REQBUFS` can only succeed if the +``V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS`` capability is set. Otherwise +:ref:`VIDIOC_REQBUFS` will return the ``EBUSY`` error code. +If ``V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS`` is set, then these buffers are +orphaned and will be freed when they are unmapped or when the exported DMABUF +fds are closed. A ``count`` value of zero frees or orphans all buffers, after +aborting or finishing any DMA in progress, an implicit :ref:`VIDIOC_STREAMOFF <VIDIOC_STREAMON>`. @@ -88,10 +100,56 @@ any DMA in progress, an implicit ``V4L2_MEMORY_DMABUF`` or ``V4L2_MEMORY_USERPTR``. See :c:type:`v4l2_memory`. * - __u32 - - ``reserved``\ [2] + - ``capabilities`` + - Set by the driver. If 0, then the driver doesn't support + capabilities. In that case all you know is that the driver is + guaranteed to support ``V4L2_MEMORY_MMAP`` and *might* support + other :c:type:`v4l2_memory` types. It will not support any others + capabilities. + + If you want to query the capabilities with a minimum of side-effects, + then this can be called with ``count`` set to 0, ``memory`` set to + ``V4L2_MEMORY_MMAP`` and ``type`` set to the buffer type. This will + free any previously allocated buffers, so this is typically something + that will be done at the start of the application. + * - __u32 + - ``reserved``\ [1] - A place holder for future extensions. Drivers and applications must set the array to zero. +.. tabularcolumns:: |p{6.1cm}|p{2.2cm}|p{8.7cm}| + +.. _v4l2-buf-capabilities: +.. _V4L2-BUF-CAP-SUPPORTS-MMAP: +.. _V4L2-BUF-CAP-SUPPORTS-USERPTR: +.. _V4L2-BUF-CAP-SUPPORTS-DMABUF: +.. _V4L2-BUF-CAP-SUPPORTS-REQUESTS: +.. _V4L2-BUF-CAP-SUPPORTS-ORPHANED-BUFS: + +.. cssclass:: longtable + +.. flat-table:: V4L2 Buffer Capabilities Flags + :header-rows: 0 + :stub-columns: 0 + :widths: 3 1 4 + + * - ``V4L2_BUF_CAP_SUPPORTS_MMAP`` + - 0x00000001 + - This buffer type supports the ``V4L2_MEMORY_MMAP`` streaming mode. + * - ``V4L2_BUF_CAP_SUPPORTS_USERPTR`` + - 0x00000002 + - This buffer type supports the ``V4L2_MEMORY_USERPTR`` streaming mode. + * - ``V4L2_BUF_CAP_SUPPORTS_DMABUF`` + - 0x00000004 + - This buffer type supports the ``V4L2_MEMORY_DMABUF`` streaming mode. + * - ``V4L2_BUF_CAP_SUPPORTS_REQUESTS`` + - 0x00000008 + - This buffer type supports :ref:`requests <media-request-api>`. + * - ``V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS`` + - 0x00000010 + - The kernel allows calling :ref:`VIDIOC_REQBUFS` while buffers are still + mapped or exported via DMABUF. These orphaned buffers will be freed + when they are unmapped or when the exported DMABUF fds are closed. Return Value ============ |