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Subject[PATCH RFC 2/4] media: v4l2-mem2mem: Add an optional job_done operation
Introduce a new optional job_done operation, which allows calling back
to the driver when a job is done. Since the job might be completed
from interrupt context where some operations are not available, having
a callback from non-atomic context allows performing these operations
upon completion of a job. This is particularly useful for releasing
access to a reference buffer, which cannot be done in atomic context.

Use the already existing v4l2_m2m_device_run_work work queue for that
and clear the M2M device current context after calling job_done in the
worker thread, so that the private data can be passed to the operation.

Delaying the current context clearing should not be a problem since the
next call to v4l2_m2m_try_run happens right after that.

Signed-off-by: Paul Kocialkowski <>
drivers/media/v4l2-core/v4l2-mem2mem.c | 8 ++++++--
include/media/v4l2-mem2mem.h | 4 ++++
2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/media/v4l2-core/v4l2-mem2mem.c b/drivers/media/v4l2-core/v4l2-mem2mem.c
index 631f4e2aa942..d5bccb0192f9 100644
--- a/drivers/media/v4l2-core/v4l2-mem2mem.c
+++ b/drivers/media/v4l2-core/v4l2-mem2mem.c
@@ -376,6 +376,11 @@ static void v4l2_m2m_device_run_work(struct work_struct *work)
struct v4l2_m2m_dev *m2m_dev =
container_of(work, struct v4l2_m2m_dev, job_work);

+ if (m2m_dev->m2m_ops->job_done && m2m_dev->curr_ctx)
+ m2m_dev->m2m_ops->job_done(m2m_dev->curr_ctx->priv);
+ m2m_dev->curr_ctx = NULL;

@@ -431,8 +436,7 @@ void v4l2_m2m_job_finish(struct v4l2_m2m_dev *m2m_dev,
m2m_dev->curr_ctx->job_flags &= ~(TRANS_QUEUED | TRANS_RUNNING);
- m2m_dev->curr_ctx = NULL;
+ /* The current context pointer is cleared after the job_done step. */
spin_unlock_irqrestore(&m2m_dev->job_spinlock, flags);

/* This instance might have more buffers ready, but since we do not
diff --git a/include/media/v4l2-mem2mem.h b/include/media/v4l2-mem2mem.h
index 43e447dcf69d..261bcd661b2d 100644
--- a/include/media/v4l2-mem2mem.h
+++ b/include/media/v4l2-mem2mem.h
@@ -40,11 +40,15 @@
* v4l2_m2m_job_finish() (as if the transaction ended normally).
* This function does not have to (and will usually not) wait
* until the device enters a state when it can be stopped.
+ * @job_done: optional. Informs the driver that the current job was completed.
+ * This can be useful to release access to extra buffers that were
+ * required for the job, such as reference buffers for decoding.
struct v4l2_m2m_ops {
void (*device_run)(void *priv);
int (*job_ready)(void *priv);
void (*job_abort)(void *priv);
+ void (*job_done)(void *priv);

struct video_device;
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