@@ -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>
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@iki.fi> --- .../DocBook/media/v4l/vidioc-prepare-buf.xml | 8 +++++--- 1 files changed, 5 insertions(+), 3 deletions(-)