Re: [PATCH v2] media: mali-c55: Require an enabled link to start a video node

[Jacopo Mondi <jacopo.mondi@ideasonboard.com>]

Hi David

On Thu, Nov 05, 2026 at 11:15:59PM +0000, David Carlier wrote:
> mali_c55_pipeline_ready() skips queues whose link is disabled, but such
> a queue can still start streaming on its own, as the video node pads

Can you elaborate on how this could happen ?

How can streaming start if you VIDIOC_STREAMON() on a capture device
without an enabled link to the resizer subdev ?

> lack MEDIA_PAD_FL_MUST_CONNECT. Stopping it later sees a ready pipeline
> and disables the ISP under the connected queues still capturing.
>
> Mark the video node pads MUST_CONNECT so that starting a disconnected
> node fails with -ENOLINK.
>
> Fixes: d5f281f3dd29 ("media: mali-c55: Add Mali-C55 ISP driver")
> Signed-off-by: David Carlier <devnexen@gmail.com>
> ---
> Changes in v2:
> - Add missing Signed-off-by.
> - Cc stable, as d5f281f3dd29 is in the stable tree.
>
> Build tested only (W=1, checkpatch --strict clean). Not tested on
> hardware; the disconnected-node STREAMON/STREAMOFF sequence is from
> code reading.
>  drivers/media/platform/arm/mali-c55/mali-c55-capture.c | 2 +-
>  drivers/media/platform/arm/mali-c55/mali-c55-params.c  | 2 +-
>  drivers/media/platform/arm/mali-c55/mali-c55-stats.c   | 2 +-

Why not the resizer ?

>  3 files changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/media/platform/arm/mali-c55/mali-c55-capture.c b/drivers/media/platform/arm/mali-c55/mali-c55-capture.c
> index ff01553026fb..2dbce550d089 100644
> --- a/drivers/media/platform/arm/mali-c55/mali-c55-capture.c
> +++ b/drivers/media/platform/arm/mali-c55/mali-c55-capture.c
> @@ -855,7 +855,7 @@ static int mali_c55_register_cap_dev(struct mali_c55 *mali_c55,
>  		goto err_destroy_mutex;
>  	}
>
> -	cap_dev->pad.flags = MEDIA_PAD_FL_SINK;
> +	cap_dev->pad.flags = MEDIA_PAD_FL_SINK | MEDIA_PAD_FL_MUST_CONNECT;
>  	ret = media_entity_pads_init(&cap_dev->vdev.entity, 1, &cap_dev->pad);
>  	if (ret)
>  		goto err_destroy_mutex;
> diff --git a/drivers/media/platform/arm/mali-c55/mali-c55-params.c b/drivers/media/platform/arm/mali-c55/mali-c55-params.c
> index 16e895e3488e..0888dc4a340e 100644
> --- a/drivers/media/platform/arm/mali-c55/mali-c55-params.c
> +++ b/drivers/media/platform/arm/mali-c55/mali-c55-params.c
> @@ -1014,7 +1014,7 @@ int mali_c55_register_params(struct mali_c55 *mali_c55)
>  	INIT_LIST_HEAD(&params->buffers.queue);
>  	spin_lock_init(&params->buffers.lock);
>
> -	params->pad.flags = MEDIA_PAD_FL_SOURCE;
> +	params->pad.flags = MEDIA_PAD_FL_SOURCE | MEDIA_PAD_FL_MUST_CONNECT;
>  	ret = media_entity_pads_init(&params->vdev.entity, 1, &params->pad);
>  	if (ret)
>  		goto err_destroy_mutex;
> diff --git a/drivers/media/platform/arm/mali-c55/mali-c55-stats.c b/drivers/media/platform/arm/mali-c55/mali-c55-stats.c
> index a9c28b090b2a..a9172781925c 100644
> --- a/drivers/media/platform/arm/mali-c55/mali-c55-stats.c
> +++ b/drivers/media/platform/arm/mali-c55/mali-c55-stats.c
> @@ -275,7 +275,7 @@ int mali_c55_register_stats(struct mali_c55 *mali_c55)
>  	INIT_LIST_HEAD(&stats->buffers.queue);
>  	spin_lock_init(&stats->buffers.lock);
>
> -	stats->pad.flags = MEDIA_PAD_FL_SINK;
> +	stats->pad.flags = MEDIA_PAD_FL_SINK | MEDIA_PAD_FL_MUST_CONNECT;
>  	ret = media_entity_pads_init(&stats->vdev.entity, 1, &stats->pad);
>  	if (ret)
>  		goto err_destroy_mutex;
> --
> 2.55.0
>
>