From: Hans Verkuil <hans.verkuil@xxxxxxxxx>
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@xxxxxxxxx>
---
include/media/videobuf2-core.h | 32 +++++++++++++++++---------------
1 file changed, 17 insertions(+), 15 deletions(-)
diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
index 6ef2d01..70ace7c 100644
--- a/include/media/videobuf2-core.h
+++ b/include/media/videobuf2-core.h
@@ -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
--
2.1.1
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