Commit ccf58cb4 authored by Hans Verkuil's avatar Hans Verkuil Committed by Mauro Carvalho Chehab

[media] vb2: fix videobuf2-core.h comments

A lot of work was done in vb2 to regulate how drivers and the vb2 core handle
buffer ownership, but inexplicably the videobuf2-core.h comments were never
updated. Do so now. The same was true for the replacement of the -ENOBUFS
mechanism by the min_buffers_needed field.
Signed-off-by: default avatarHans Verkuil <>
Signed-off-by: default avatarMauro Carvalho Chehab <>
parent 5d0360a4
......@@ -294,15 +294,19 @@ struct vb2_buffer {
* of already queued buffers in count parameter; driver
* can return an error if hardware fails, in that case all
* buffers that have been already given by the @buf_queue
* callback are invalidated.
* If there were not enough queued buffers to start
* streaming, then this callback returns -ENOBUFS, and the
* vb2 core will retry calling @start_streaming when a new
* buffer is queued.
* callback are to be returned by the driver by calling
* @vb2_buffer_done(VB2_BUF_STATE_DEQUEUED).
* If you need a minimum number of buffers before you can
* start streaming, then set @min_buffers_needed in the
* vb2_queue structure. If that is non-zero then
* start_streaming won't be called until at least that
* many buffers have been queued up by userspace.
* @stop_streaming: called when 'streaming' state must be disabled; driver
* should stop any DMA transactions or wait until they
* finish and give back all buffers it got from buf_queue()
* callback; may use vb2_wait_for_all_buffers() function
* callback by calling @vb2_buffer_done() with either
* vb2_wait_for_all_buffers() function
* @buf_queue: passes buffer vb to the driver; driver may start
* hardware operation on this buffer; driver should give
* the buffer back by calling vb2_buffer_done() function;
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