media/v4l/userp.rst

1 .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
13 :ref:`VIDIOC_QUERYCAP` ioctl is set. If the
15 must be determined by calling the :ref:`VIDIOC_REQBUFS` ioctl
21 data are exchanged, these pointers and meta-information are passed in
23 :c:type:`v4l2_plane` in the multi-planar API case). The
25 :ref:`VIDIOC_REQBUFS` with the desired buffer type.
28 :ref:`VIDIOC_QUERYBUF <VIDIOC_QUERYBUF>` ioctl.
33 .. code-block:: c
41     if (ioctl (fd, VIDIOC_REQBUFS, &reqbuf) == -1) {
51 :ref:`VIDIOC_QBUF <VIDIOC_QBUF>` ioctl. Although buffers are commonly
53 :ref:`VIDIOC_QBUF <VIDIOC_QBUF>` call. If required by the hardware the
61 :ref:`VIDIOC_DQBUF <VIDIOC_QBUF>` ioctl. The driver can unlock the
64 :ref:`VIDIOC_STREAMOFF <VIDIOC_STREAMON>` is called,
65 :ref:`VIDIOC_REQBUFS`, or when the device is closed.
74 application waits until a filled buffer can be dequeued, and re-enqueues
80 more buffers can be dequeued. By default :ref:`VIDIOC_DQBUF
83 :ref:`VIDIOC_DQBUF <VIDIOC_QBUF>` returns immediately with an ``EAGAIN``
84 error code when no buffer is available. The :ref:`select()
85 <func-select>` or :c:func:`poll()` function are always
89 :ref:`VIDIOC_STREAMON <VIDIOC_STREAMON>` and
90 :ref:`VIDIOC_STREAMOFF <VIDIOC_STREAMON>` ioctl.
94    :ref:`VIDIOC_STREAMOFF <VIDIOC_STREAMON>` removes all buffers from
102 :ref:`VIDIOC_REQBUFS <VIDIOC_REQBUFS>`, :ref:`VIDIOC_QBUF <VIDIOC_QBUF>`,
103 :ref:`VIDIOC_DQBUF <VIDIOC_QBUF>`, :ref:`VIDIOC_STREAMON <VIDIOC_STREAMON>`
104 and :ref:`VIDIOC_STREAMOFF <VIDIOC_STREAMON>` ioctls, the
105 :c:func:`select()` and :c:func:`poll()` function. [#f2]_
109    Anyway, the process of swapping, locking or generating scatter-gather
120    At the driver level :c:func:`select()` and :c:func:`poll()` are
121    the same, and :c:func:`select()` is too important to be optional.