Add note to documentation of VIDIOC_PREPARE_BUF that the preparation done by the IOCTL may include locking buffers to system memory and creating DMA mappings for them. Signed-off-by: Sakari Ailus <sakari.ailus@xxxxxx> --- .../DocBook/media/v4l/vidioc-prepare-buf.xml | 8 +++++--- 1 files changed, 5 insertions(+), 3 deletions(-) diff --git a/Documentation/DocBook/media/v4l/vidioc-prepare-buf.xml b/Documentation/DocBook/media/v4l/vidioc-prepare-buf.xml index 509e752..7177c2f 100644 --- a/Documentation/DocBook/media/v4l/vidioc-prepare-buf.xml +++ b/Documentation/DocBook/media/v4l/vidioc-prepare-buf.xml @@ -52,9 +52,11 @@ <constant>VIDIOC_PREPARE_BUF</constant> ioctl to pass ownership of the buffer to the driver before actually enqueuing it, using the <constant>VIDIOC_QBUF</constant> 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. In case such cache operations are -not required, the application can use one of +Such preparations may include locking the buffer to system memory and +creating DMA mapping for it (on the first time +<constant>VIDIOC_PREPARE_BUF</constant> is called), cache invalidation or +cleaning. Performing them in advance saves time during the actual I/O. In +case such cache operations are not required, the application can use one of <constant>V4L2_BUF_FLAG_NO_CACHE_INVALIDATE</constant> and <constant>V4L2_BUF_FLAG_NO_CACHE_CLEAN</constant> flags to skip the respective step.</para> -- 1.7.2.5 -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
