media/v4l/userp.rst

1 .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
14 particular user pointer method (not only memory mapping) is supported
21 data are exchanged, these pointers and meta-information are passed in
23 :c:type:`v4l2_plane` in the multi-planar API case). The
26 No buffers (planes) are allocated beforehand, consequently they are not
33 .. code-block:: c
41     if (ioctl (fd, VIDIOC_REQBUFS, &reqbuf) == -1) {
43 	    printf ("Video capturing or user pointer streaming is not supported\\n");
57 swapped out to disk they are brought back and finally locked in physical
66 Applications must take care not to free buffers without dequeuing.
68 Secondly the driver will not be notified when the memory is returned to
74 application waits until a filled buffer can be dequeued, and re-enqueues
85 <func-select>` or :c:func:`poll()` function are always
108    We expect that frequently used buffers are typically not swapped out.
109    Anyway, the process of swapping, locking or generating scatter-gather
115    the pages of empty buffers in the incoming queue need not be saved to