+ Sakari and Hans
This patch is needed by this series, but I think it could also be
reviewed and merged standalone already.
On Wed, Jun 15, 2022 at 04:10:48AM +0900, Paul Elder wrote:
> From: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
>
> Drivers typically extend the v4l2_async_subdev structure by embedding it
> in a driver-specific structure, to store per-subdev custom data. The
> v4l2_async_subdev instances are freed by the v4l2-async framework, which
> makes this mechanism cumbersome to use safely when custom data needs
> special treatment to be destroyed (such as freeing additional memory, or
> releasing references to kernel objects).
>
> To ease this, add a .destroy() operation to the
> v4l2_async_notifier_operations structure. The operation is called right
> before the v4l2_async_subdev is freed, giving drivers a chance to
> destroy data if needed.
>
> Signed-off-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
> ---
> Documentation/driver-api/media/v4l2-subdev.rst | 6 ++++++
> drivers/media/v4l2-core/v4l2-async.c | 10 ++++++++++
> include/media/v4l2-async.h | 2 ++
> 3 files changed, 18 insertions(+)
>
> diff --git a/Documentation/driver-api/media/v4l2-subdev.rst b/Documentation/driver-api/media/v4l2-subdev.rst
> index cf3b52bdbfb9..6f8d79926aa5 100644
> --- a/Documentation/driver-api/media/v4l2-subdev.rst
> +++ b/Documentation/driver-api/media/v4l2-subdev.rst
> @@ -243,6 +243,12 @@ notifier callback is called. After all subdevices have been located the
> .complete() callback is called. When a subdevice is removed from the
> system the .unbind() method is called. All three callbacks are optional.
>
> +Drivers can store any type of custom data in their driver-specific
> +:c:type:`v4l2_async_subdev` wrapper. If any of that data requires special
> +handling when the structure is freed, drivers must implement the ``.destroy()``
> +notifier callback. The framework will call it right before freeing the
> +:c:type:`v4l2_async_subdev`.
> +
> Calling subdev operations
> ~~~~~~~~~~~~~~~~~~~~~~~~~
>
> diff --git a/drivers/media/v4l2-core/v4l2-async.c b/drivers/media/v4l2-core/v4l2-async.c
> index c6995718237a..735dede624b8 100644
> --- a/drivers/media/v4l2-core/v4l2-async.c
> +++ b/drivers/media/v4l2-core/v4l2-async.c
> @@ -52,6 +52,15 @@ static int v4l2_async_nf_call_complete(struct v4l2_async_notifier *n)
> return n->ops->complete(n);
> }
>
> +static void v4l2_async_nf_call_destroy(struct v4l2_async_notifier *n,
> + struct v4l2_async_subdev *asd)
> +{
> + if (!n->ops || !n->ops->destroy)
> + return;
> +
> + n->ops->destroy(asd);
> +}
> +
> static bool match_i2c(struct v4l2_async_notifier *notifier,
> struct v4l2_subdev *sd, struct v4l2_async_subdev *asd)
> {
> @@ -626,6 +635,7 @@ static void __v4l2_async_nf_cleanup(struct v4l2_async_notifier *notifier)
> }
>
> list_del(&asd->asd_list);
> + v4l2_async_nf_call_destroy(notifier, asd);
> kfree(asd);
> }
> }
> diff --git a/include/media/v4l2-async.h b/include/media/v4l2-async.h
> index 13ff3ad948f4..25eb1d138c06 100644
> --- a/include/media/v4l2-async.h
> +++ b/include/media/v4l2-async.h
> @@ -81,6 +81,7 @@ struct v4l2_async_subdev {
> * @complete: All subdevices have been probed successfully. The complete
> * callback is only executed for the root notifier.
> * @unbind: a subdevice is leaving
> + * @destroy: the asd is about to be freed
> */
> struct v4l2_async_notifier_operations {
> int (*bound)(struct v4l2_async_notifier *notifier,
> @@ -90,6 +91,7 @@ struct v4l2_async_notifier_operations {
> void (*unbind)(struct v4l2_async_notifier *notifier,
> struct v4l2_subdev *subdev,
> struct v4l2_async_subdev *asd);
> + void (*destroy)(struct v4l2_async_subdev *asd);
> };
>
> /**
--
Regards,
Laurent Pinchart
