| .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later |
| .. c:namespace:: V4L |
| |
| .. _VIDIOC_PREPARE_BUF: |
| |
| ************************ |
| ioctl VIDIOC_PREPARE_BUF |
| ************************ |
| |
| Name |
| ==== |
| |
| VIDIOC_PREPARE_BUF - Prepare a buffer for I/O |
| |
| Synopsis |
| ======== |
| |
| .. c:macro:: VIDIOC_PREPARE_BUF |
| |
| ``int ioctl(int fd, VIDIOC_PREPARE_BUF, struct v4l2_buffer *argp)`` |
| |
| Arguments |
| ========= |
| |
| ``fd`` |
| File descriptor returned by :c:func:`open()`. |
| |
| ``argp`` |
| Pointer to struct :c:type:`v4l2_buffer`. |
| |
| Description |
| =========== |
| |
| Applications can optionally call the :ref:`VIDIOC_PREPARE_BUF` ioctl to |
| pass ownership of the buffer to the driver before actually enqueuing it, |
| using the :ref:`VIDIOC_QBUF <VIDIOC_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. |
| |
| The struct :c:type:`v4l2_buffer` structure is specified in |
| :ref:`buffer`. |
| |
| 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. |
