media: v4l2: Add ignore_streaming flag

Add a new flag to the `struct v4l2_m2m_dev` to toggle whether a queue
must be streaming in order to allow queuing jobs to the ready queue.
Currently, both queues (CAPTURE & OUTPUT) must be streaming in order to
allow adding new jobs. This behavior limits the usability of M2M for
some drivers, as these have to be able, to perform analysis of the
sequence to ensure, that userspace prepares the CAPTURE queue correctly.

Signed-off-by: Sebastian Fricke <sebastian.fricke@collabora.com>
Signed-off-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>

include/media/v4l2-mem2mem.h

@@ -84,6 +84,12 @@ struct v4l2_m2m_queue_ctx {
  * @last_src_buf: indicate the last source buffer for draining
  * @next_buf_last: next capture queud buffer will be tagged as last
  * @has_stopped: indicate the device has been stopped
+ * @ignore_cap_streaming: If true, job_ready can be called even if the CAPTURE
+ *			  queue is not streaming. This allows firmware to
+ *			  analyze the bitstream header which arrives on the
+ *			  OUTPUT queue. The driver must implement the job_ready
+ *			  callback correctly to make sure that the requirements
+ *			  for actual decoding are met.
  * @m2m_dev: opaque pointer to the internal data to handle M2M context
  * @cap_q_ctx: Capture (output to memory) queue context
  * @out_q_ctx: Output (input from memory) queue context
@@ -106,6 +112,7 @@ struct v4l2_m2m_ctx {
 	struct vb2_v4l2_buffer		*last_src_buf;
 	bool				next_buf_last;
 	bool				has_stopped;
+	bool				ignore_cap_streaming;
 
 	/* internal use only */
 	struct v4l2_m2m_dev		*m2m_dev;