Re: [PATCH 1/3] media: Fix ALSA and DVB representation at media controller API

[Hans Verkuil <hverkuil@xs4all.nl>]

On 01/26/2015 01:47 PM, Mauro Carvalho Chehab wrote:
> The previous provision for DVB media controller support were to
> define an ID (likely meaning the adapter number) for the DVB
> devnodes.
> 
> This is just plain wrong. Just like V4L, DVB devices (and ALSA,
> or whatever) are identified via a (major, minor) tuple.
> 
> This is enough to uniquely identify a devnode, no matter what
> API it implements.
> 
> So, before we go too far, let's mark the old v4l, dvb and alsa
> "devnode" info as deprecated, and just call it as "dev".
> 
> As we don't want to break compilation on already existing apps,
> let's just keep the old definitions as-is, adding a note that
> those are deprecated at media-entity.h.
> 
> Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
> 
> diff --git a/drivers/media/v4l2-core/v4l2-dev.c b/drivers/media/v4l2-core/v4l2-dev.c
> index 86bb93fd7db8..d89d5cb465d9 100644
> --- a/drivers/media/v4l2-core/v4l2-dev.c
> +++ b/drivers/media/v4l2-core/v4l2-dev.c
> @@ -943,8 +943,8 @@ int __video_register_device(struct video_device *vdev, int type, int nr,
>  	    vdev->vfl_type != VFL_TYPE_SUBDEV) {
>  		vdev->entity.type = MEDIA_ENT_T_DEVNODE_V4L;
>  		vdev->entity.name = vdev->name;
> -		vdev->entity.info.v4l.major = VIDEO_MAJOR;
> -		vdev->entity.info.v4l.minor = vdev->minor;
> +		vdev->entity.info.dev.major = VIDEO_MAJOR;
> +		vdev->entity.info.dev.minor = vdev->minor;
>  		ret = media_device_register_entity(vdev->v4l2_dev->mdev,
>  			&vdev->entity);
>  		if (ret < 0)
> diff --git a/drivers/media/v4l2-core/v4l2-device.c b/drivers/media/v4l2-core/v4l2-device.c
> index 015f92aab44a..204cc67c84e8 100644
> --- a/drivers/media/v4l2-core/v4l2-device.c
> +++ b/drivers/media/v4l2-core/v4l2-device.c
> @@ -248,8 +248,8 @@ int v4l2_device_register_subdev_nodes(struct v4l2_device *v4l2_dev)
>  			goto clean_up;
>  		}
>  #if defined(CONFIG_MEDIA_CONTROLLER)
> -		sd->entity.info.v4l.major = VIDEO_MAJOR;
> -		sd->entity.info.v4l.minor = vdev->minor;
> +		sd->entity.info.dev.major = VIDEO_MAJOR;
> +		sd->entity.info.dev.minor = vdev->minor;
>  #endif
>  		sd->devnode = vdev;
>  	}
> diff --git a/include/media/media-entity.h b/include/media/media-entity.h
> index e00459185d20..d6d74bcfe183 100644
> --- a/include/media/media-entity.h
> +++ b/include/media/media-entity.h
> @@ -87,17 +87,7 @@ struct media_entity {
>  		struct {
>  			u32 major;
>  			u32 minor;
> -		} v4l;
> -		struct {
> -			u32 major;
> -			u32 minor;
> -		} fb;
> -		struct {
> -			u32 card;
> -			u32 device;
> -			u32 subdevice;
> -		} alsa;

I don't think the alsa entity information can be replaced by major/minor.
In particular you will loose the subdevice information which you need as
well. In addition, alsa devices are almost never referenced via major and
minor numbers, but always by card/device/subdevice numbers.

> -		int dvb;
> +		} dev;
>  
>  		/* Sub-device specifications */
>  		/* Nothing needed yet */
> diff --git a/include/uapi/linux/media.h b/include/uapi/linux/media.h
> index d847c760e8f0..418f4fec391a 100644
> --- a/include/uapi/linux/media.h
> +++ b/include/uapi/linux/media.h
> @@ -78,6 +78,20 @@ struct media_entity_desc {
>  		struct {
>  			__u32 major;
>  			__u32 minor;
> +		} dev;
> +
> +#if 1
> +		/*
> +		 * DEPRECATED: previous node specifications. Kept just to
> +		 * avoid breaking compilation, but media_entity_desc.dev
> +		 * should be used instead. In particular, alsa and dvb
> +		 * fields below are wrong: for all devnodes, there should
> +		 * be just major/minor inside the struct, as this is enough
> +		 * to represent any devnode, no matter what type.
> +		 */
> +		struct {
> +			__u32 major;
> +			__u32 minor;
>  		} v4l;
>  		struct {
>  			__u32 major;
> @@ -89,6 +103,7 @@ struct media_entity_desc {
>  			__u32 subdevice;
>  		} alsa;
>  		int dvb;

I wouldn't merge all the v4l/fb/etc. structs into one struct. That will make it
difficult in the future if you need to add a field for e.g. v4l entities.

So I would keep the v4l, fb and alsa structs, and just add a new struct for
dvb. I wonder if the dvb field can't just be replaced since I doubt anyone is
using it. And even if someone does, then it can't be right since a single
int isn't enough and never worked anyway.

Regards,

	Hans

> +#endif
>  
>  		/* Sub-device specifications */
>  		/* Nothing needed yet */
>