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[media] videobuf2-core.h: improve documentation

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Document that drivers can access/modify the buffer contents in buf_prepare
and buf_finish. That was not clearly stated before.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Acked-by: Pawel Osciak <pawel@osciak.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
This commit is contained in:
Hans Verkuil 2014-11-18 09:50:57 -03:00 committed by Mauro Carvalho Chehab
parent ef33d901db
commit cf227429c7
1 changed files with 17 additions and 15 deletions
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32
include/media/videobuf2-core.h
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@ -270,22 +270,24 @@ struct vb2_buffer {
* queue setup from completing successfully; optional.
* @buf_prepare: called every time the buffer is queued from userspace
* and from the VIDIOC_PREPARE_BUF ioctl; drivers may
* perform any initialization required before each hardware
* operation in this callback; drivers that support
* VIDIOC_CREATE_BUFS must also validate the buffer size;
* if an error is returned, the buffer will not be queued
* in driver; optional.
* perform any initialization required before each
* hardware operation in this callback; drivers can
* access/modify the buffer here as it is still synced for
* the CPU; drivers that support VIDIOC_CREATE_BUFS must
* also validate the buffer size; if an error is returned,
* the buffer will not be queued in driver; optional.
* @buf_finish: called before every dequeue of the buffer back to
* userspace; drivers may perform any operations required
* before userspace accesses the buffer; optional. The
* buffer state can be one of the following: DONE and
* ERROR occur while streaming is in progress, and the
* PREPARED state occurs when the queue has been canceled
* and all pending buffers are being returned to their
* default DEQUEUED state. Typically you only have to do
* something if the state is VB2_BUF_STATE_DONE, since in
* all other cases the buffer contents will be ignored
* anyway.
* userspace; the buffer is synced for the CPU, so drivers
* can access/modify the buffer contents; drivers may
* perform any operations required before userspace
* accesses the buffer; optional. The buffer state can be
* one of the following: DONE and ERROR occur while
* streaming is in progress, and the PREPARED state occurs
* when the queue has been canceled and all pending
* buffers are being returned to their default DEQUEUED
* state. Typically you only have to do something if the
* state is VB2_BUF_STATE_DONE, since in all other cases
* the buffer contents will be ignored anyway.
* @buf_cleanup: called once before the buffer is freed; drivers may
* perform any additional cleanup; optional.
* @start_streaming: called once to enter 'streaming' state; the driver may