1*4882a593Smuzhiyun.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later 2*4882a593Smuzhiyun.. c:namespace:: V4L 3*4882a593Smuzhiyun 4*4882a593Smuzhiyun.. _VIDIOC_PREPARE_BUF: 5*4882a593Smuzhiyun 6*4882a593Smuzhiyun************************ 7*4882a593Smuzhiyunioctl VIDIOC_PREPARE_BUF 8*4882a593Smuzhiyun************************ 9*4882a593Smuzhiyun 10*4882a593SmuzhiyunName 11*4882a593Smuzhiyun==== 12*4882a593Smuzhiyun 13*4882a593SmuzhiyunVIDIOC_PREPARE_BUF - Prepare a buffer for I/O 14*4882a593Smuzhiyun 15*4882a593SmuzhiyunSynopsis 16*4882a593Smuzhiyun======== 17*4882a593Smuzhiyun 18*4882a593Smuzhiyun.. c:macro:: VIDIOC_PREPARE_BUF 19*4882a593Smuzhiyun 20*4882a593Smuzhiyun``int ioctl(int fd, VIDIOC_PREPARE_BUF, struct v4l2_buffer *argp)`` 21*4882a593Smuzhiyun 22*4882a593SmuzhiyunArguments 23*4882a593Smuzhiyun========= 24*4882a593Smuzhiyun 25*4882a593Smuzhiyun``fd`` 26*4882a593Smuzhiyun File descriptor returned by :c:func:`open()`. 27*4882a593Smuzhiyun 28*4882a593Smuzhiyun``argp`` 29*4882a593Smuzhiyun Pointer to struct :c:type:`v4l2_buffer`. 30*4882a593Smuzhiyun 31*4882a593SmuzhiyunDescription 32*4882a593Smuzhiyun=========== 33*4882a593Smuzhiyun 34*4882a593SmuzhiyunApplications can optionally call the :ref:`VIDIOC_PREPARE_BUF` ioctl to 35*4882a593Smuzhiyunpass ownership of the buffer to the driver before actually enqueuing it, 36*4882a593Smuzhiyunusing the :ref:`VIDIOC_QBUF <VIDIOC_QBUF>` ioctl, and to prepare it for future I/O. Such 37*4882a593Smuzhiyunpreparations may include cache invalidation or cleaning. Performing them 38*4882a593Smuzhiyunin advance saves time during the actual I/O. 39*4882a593Smuzhiyun 40*4882a593SmuzhiyunThe struct :c:type:`v4l2_buffer` structure is specified in 41*4882a593Smuzhiyun:ref:`buffer`. 42*4882a593Smuzhiyun 43*4882a593SmuzhiyunReturn Value 44*4882a593Smuzhiyun============ 45*4882a593Smuzhiyun 46*4882a593SmuzhiyunOn success 0 is returned, on error -1 and the ``errno`` variable is set 47*4882a593Smuzhiyunappropriately. The generic error codes are described at the 48*4882a593Smuzhiyun:ref:`Generic Error Codes <gen-errors>` chapter. 49*4882a593Smuzhiyun 50*4882a593SmuzhiyunEBUSY 51*4882a593Smuzhiyun File I/O is in progress. 52*4882a593Smuzhiyun 53*4882a593SmuzhiyunEINVAL 54*4882a593Smuzhiyun The buffer ``type`` is not supported, or the ``index`` is out of 55*4882a593Smuzhiyun bounds, or no buffers have been allocated yet, or the ``userptr`` or 56*4882a593Smuzhiyun ``length`` are invalid. 57