linux-kernel - [PATCH RFC 2/4] media: v4l2-mem2mem: Add an optional job

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Date:   Mon, 14 Jan 2019 14:38:37 +0100
From:   Paul Kocialkowski <paul.kocialkowski@...tlin.com>
To:     linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        devel@...verdev.osuosl.org, linux-arm-kernel@...ts.infradead.org,
        linux-sunxi@...glegroups.com
Cc:     Pawel Osciak <pawel@...iak.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Maxime Ripard <maxime.ripard@...tlin.com>,
        Paul Kocialkowski <paul.kocialkowski@...tlin.com>,
        Randy Li <ayaka@...lik.info>,
        Hans Verkuil <hverkuil@...all.nl>,
        Ezequiel Garcia <ezequiel@...labora.com>,
        Tomasz Figa <tfiga@...omium.org>,
        Alexandre Courbot <acourbot@...omium.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>
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 <paul.kocialkowski@...tlin.com>
---
 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;
+
 	v4l2_m2m_try_run(m2m_dev);
 }
 
@@ -431,8 +436,7 @@ void v4l2_m2m_job_finish(struct v4l2_m2m_dev *m2m_dev,
 	list_del(&m2m_dev->curr_ctx->queue);
 	m2m_dev->curr_ctx->job_flags &= ~(TRANS_QUEUED | TRANS_RUNNING);
 	wake_up(&m2m_dev->curr_ctx->finished);
-	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;
-- 
2.20.1