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media: v4l2-mem2mem: Add a kref to the v4l2_m2m_dev structure

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Adding a reference count to the v4l2_m2m_dev structure allow safely
sharing it across multiple hardware nodes. This can be used to prevent
running jobs concurrently on m2m cores that have some internal resource
sharing.

Signed-off-by: Ming Qian <ming.qian@oss.nxp.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Signed-off-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>
[hverkuil: fix typos in v4l2_m2m_put documentation]
This commit is contained in:
Nicolas Dufresne 2025-12-05 09:54:24 +08:00 • committed by Hans Verkuil
parent 3e92d7e493
commit db6b97a4f8
2 changed files with 44 additions and 0 deletions
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23
drivers/media/v4l2-core/v4l2-mem2mem.c
View file

@ -90,6 +90,7 @@ static const char * const m2m_entity_name[] = {
* @job_work: worker to run queued jobs.
* @job_queue_flags: flags of the queue status, %QUEUE_PAUSED.
* @m2m_ops: driver callbacks
* @kref: device reference count
*/
struct v4l2_m2m_dev {
struct v4l2_m2m_ctx *curr_ctx;
@ -109,6 +110,8 @@ struct v4l2_m2m_dev {
unsigned long job_queue_flags;
const struct v4l2_m2m_ops *m2m_ops;
struct kref kref;
};
static struct v4l2_m2m_queue_ctx *get_queue_ctx(struct v4l2_m2m_ctx *m2m_ctx,
@ -1200,6 +1203,7 @@ struct v4l2_m2m_dev *v4l2_m2m_init(const struct v4l2_m2m_ops *m2m_ops)
INIT_LIST_HEAD(&m2m_dev->job_queue);
spin_lock_init(&m2m_dev->job_spinlock);
INIT_WORK(&m2m_dev->job_work, v4l2_m2m_device_run_work);
kref_init(&m2m_dev->kref);
return m2m_dev;
}
@ -1211,6 +1215,25 @@ void v4l2_m2m_release(struct v4l2_m2m_dev *m2m_dev)
}
EXPORT_SYMBOL_GPL(v4l2_m2m_release);
void v4l2_m2m_get(struct v4l2_m2m_dev *m2m_dev)
{
kref_get(&m2m_dev->kref);
}
EXPORT_SYMBOL_GPL(v4l2_m2m_get);
static void v4l2_m2m_release_from_kref(struct kref *kref)
{
struct v4l2_m2m_dev *m2m_dev = container_of(kref, struct v4l2_m2m_dev, kref);
v4l2_m2m_release(m2m_dev);
}
void v4l2_m2m_put(struct v4l2_m2m_dev *m2m_dev)
{
kref_put(&m2m_dev->kref, v4l2_m2m_release_from_kref);
}
EXPORT_SYMBOL_GPL(v4l2_m2m_put);
struct v4l2_m2m_ctx *v4l2_m2m_ctx_init(struct v4l2_m2m_dev *m2m_dev,
void *drv_priv,
int (*queue_init)(void *priv, struct vb2_queue *src_vq, struct vb2_queue *dst_vq))

21
include/media/v4l2-mem2mem.h
View file

@ -547,6 +547,27 @@ v4l2_m2m_register_media_controller(struct v4l2_m2m_dev *m2m_dev,
*/
void v4l2_m2m_release(struct v4l2_m2m_dev *m2m_dev);
/**
* v4l2_m2m_get() - take a reference to the m2m_dev structure
*
* @m2m_dev: opaque pointer to the internal data to handle M2M context
*
* This is used to share the M2M device across multiple devices. This
* can be used to avoid scheduling two hardware nodes concurrently.
*/
void v4l2_m2m_get(struct v4l2_m2m_dev *m2m_dev);
/**
* v4l2_m2m_put() - remove a reference to the m2m_dev structure
*
* @m2m_dev: opaque pointer to the internal data to handle M2M context
*
* Once the M2M device has no more references, v4l2_m2m_release() will be
* called automatically. Users of this method should never call
* v4l2_m2m_release() directly. See v4l2_m2m_get() for more details.
*/
void v4l2_m2m_put(struct v4l2_m2m_dev *m2m_dev);
/**
* v4l2_m2m_ctx_init() - allocate and initialize a m2m context
*