Re: [PATCH v5 22/24] v4l: subdev: add v4l2_subdev_get_format_dir()

[Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>]

Hi Laurent,

On 18/04/2021 22:04, Laurent Pinchart wrote:
> Hi Tomi,
> 
> Thank you for the patch.
> 
> On Thu, Apr 15, 2021 at 04:04:48PM +0300, Tomi Valkeinen wrote:
>> Add v4l2_subdev_get_format_dir() which can be used to find subdev format
>> for a specific stream on a multiplexed pad. The function will follow the
>> routes and links until it finds a non-multiplexed pad.
>>
>> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
>> ---
>>   drivers/media/v4l2-core/v4l2-subdev.c | 96 +++++++++++++++++++++++++++
>>   include/media/v4l2-subdev.h           | 26 ++++++++
>>   2 files changed, 122 insertions(+)
>>
>> diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
>> index 7a4f71d8c6c3..430dbdaab080 100644
>> --- a/drivers/media/v4l2-core/v4l2-subdev.c
>> +++ b/drivers/media/v4l2-core/v4l2-subdev.c
>> @@ -998,6 +998,102 @@ bool v4l2_subdev_has_route(struct v4l2_subdev_krouting *routing,
>>   }
>>   EXPORT_SYMBOL_GPL(v4l2_subdev_has_route);
>>   
>> +int v4l2_subdev_get_format_dir(struct media_pad *pad, u16 stream,
>> +			       enum v4l2_direction dir,
>> +			       struct v4l2_subdev_format *fmt)
>> +{
>> +	struct device *dev = pad->entity->graph_obj.mdev->dev;
>> +	int ret;
>> +	int i;
>> +
>> +	dev_dbg(dev, "%s '%s':%u:%u %s\n", __func__,
>> +		pad->entity->name, pad->index, stream,
>> +		dir == V4L2_DIR_SOURCEWARD ? "sourceward" : "sinkward");
>> +
>> +	while (true) {
>> +		struct v4l2_subdev_krouting routing;
>> +		struct v4l2_subdev_route *route;
>> +
>> +		if (pad->entity->obj_type != MEDIA_ENTITY_TYPE_V4L2_SUBDEV)
>> +			return -EINVAL;
>> +
>> +		ret = v4l2_subdev_link_validate_get_format(pad, fmt);
>> +		if (ret == 0)
>> +			return 0;
>> +		else if (ret != -ENOIOCTLCMD)
>> +			return ret;
>> +
>> +		if (pad->flags &
>> +		    (dir == V4L2_DIR_SINKWARD ? MEDIA_PAD_FL_SOURCE :
>> +						MEDIA_PAD_FL_SINK)) {
>> +			pad = media_entity_remote_pad(pad);
>> +
>> +			if (!pad)
>> +				return -EINVAL;
>> +
>> +			if (pad->entity->obj_type != MEDIA_ENTITY_TYPE_V4L2_SUBDEV)
>> +				return -EINVAL;
>> +
>> +			ret = v4l2_subdev_link_validate_get_format(pad, fmt);
>> +			if (ret == 0)
>> +				return 0;
>> +			else if (ret != -ENOIOCTLCMD)
>> +				return ret;
>> +		}
>> +
>> +		ret = v4l2_subdev_get_krouting(media_entity_to_v4l2_subdev(pad->entity), &routing);
>> +		if (ret)
>> +			return ret;
>> +
>> +		route = NULL;
>> +		for (i = 0; i < routing.num_routes; ++i) {
>> +			u16 near_pad = dir == V4L2_DIR_SINKWARD ?
>> +					       routing.routes[i].sink_pad :
>> +					       routing.routes[i].source_pad;
>> +			u16 near_stream = dir == V4L2_DIR_SINKWARD ?
>> +						  routing.routes[i].sink_stream :
>> +						  routing.routes[i].source_stream;
>> +
>> +			if (!(routing.routes[i].flags & V4L2_SUBDEV_ROUTE_FL_ACTIVE))
>> +				continue;
>> +
>> +			if (near_pad != pad->index)
>> +				continue;
>> +
>> +			if (near_stream != stream)
>> +				continue;
>> +
>> +			if (route) {
>> +				dev_err(dev,
>> +					"%s: '%s' has multiple active routes for stream %u\n",
>> +					__func__, pad->entity->name, stream);
>> +				v4l2_subdev_free_routing(&routing);
>> +				return -EINVAL;
>> +			}
>> +
>> +			route = &routing.routes[i];
>> +		}
>> +
>> +		if (!route) {
>> +			dev_err(dev, "%s: no route found in '%s' for stream %u\n",
>> +				__func__, pad->entity->name, stream);
>> +			v4l2_subdev_free_routing(&routing);
>> +			return -EINVAL;
>> +		}
>> +
>> +		if (dir == V4L2_DIR_SINKWARD) {
>> +			pad = &pad->entity->pads[route->source_pad];
>> +			stream = route->source_stream;
>> +		} else {
>> +			pad = &pad->entity->pads[route->sink_pad];
>> +			stream = route->sink_stream;
>> +		}
>> +
>> +		v4l2_subdev_free_routing(&routing);
>> +	}
>> +}
>> +EXPORT_SYMBOL_GPL(v4l2_subdev_get_format_dir);
>> +
>>   int v4l2_subdev_link_validate(struct media_link *link)
>>   {
>>   	struct v4l2_subdev *sink;
>> diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
>> index 1843b77dd843..730631f9a091 100644
>> --- a/include/media/v4l2-subdev.h
>> +++ b/include/media/v4l2-subdev.h
>> @@ -1239,4 +1239,30 @@ void v4l2_subdev_cpy_routing(struct v4l2_subdev_krouting *dst,
>>   bool v4l2_subdev_has_route(struct v4l2_subdev_krouting *routing,
>>   			   unsigned int pad0, unsigned int pad1);
>>   
>> +/**
>> + * enum v4l2_direction - Direction either towards the source or the sink
>> + *
>> + * @V4L2_DIR_SOURCEWARD: Direction towards the source.
>> + * @V4L2_DIR_SINKWARD: Direction towards the sink.
>> + */
>> +enum v4l2_direction {
>> +	V4L2_DIR_SOURCEWARD,
>> +	V4L2_DIR_SINKWARD,
>> +};
>> +
>> +/**
>> + * v4l2_subdev_get_format_dir() - Find format by following streams
> 
> The name is a bit cryptic, and the usage pattern error-prone. Can we do
> better ?  In particular, if we could limit the usage of this function to
> be called on a non-multiplexed pad, we could drop the stream argument.
> Deducing the direction argument from the type of pad would also make the
> API simpler.

Hmm, but that's not what the function does. It follows a specific 
stream, from a multiplexed pad, so it has to get the stream as a parameter.

We can't deduct the direction from the type of the pad. We can of course 
define that given a source pad this function goes sourceward. But if 
that's not what the caller wants, then the caller needs to first follow 
the stream either direction to get a sink pad, and then call this 
function, which doesn't make sense.

>> + * @pad: The pad from which to start the search
>> + * @stream: The stream for which we want to find the format
>> + * @dir: The direction of the search
>> + * @fmt: Pointer to &struct v4l2_subdev_format where the found format is stored
>> + *
>> + * This function attempts to find v4l2_subdev_format for a specific stream on a
>> + * multiplexed pad by following the stream using routes and links to the specified
>> + * direction, until a non-multiplexed pad is found.
>> + */
>> +int v4l2_subdev_get_format_dir(struct media_pad *pad, u16 stream,
>> +			       enum v4l2_direction dir,
>> +			       struct v4l2_subdev_format *fmt);
>> +
>>   #endif
>