Re: [PATCH v7 21/27] v4l: subdev: routing kernel helper functions

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Tomi,

Thank you for the patch.

On Mon, May 24, 2021 at 01:44:02PM +0300, Tomi Valkeinen wrote:
> Add helper functions for routing. These helpers make it easier for the
> drivers to use struct v4l2_subdev_krouting.
> 
> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
> ---
>  drivers/media/v4l2-core/v4l2-subdev.c | 100 ++++++++++++++++++++++++++
>  include/media/v4l2-subdev.h           |  69 ++++++++++++++++++
>  2 files changed, 169 insertions(+)
> 
> diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
> index 28e84453fe28..ef18682dbc6f 100644
> --- a/drivers/media/v4l2-core/v4l2-subdev.c
> +++ b/drivers/media/v4l2-core/v4l2-subdev.c
> @@ -912,6 +912,106 @@ v4l2_subdev_link_validate_get_format(struct media_pad *pad,
>  	return -EINVAL;
>  }
>  
> +int v4l2_subdev_get_routing(struct v4l2_subdev *sd,
> +			    struct v4l2_subdev_state *state,
> +			    struct v4l2_subdev_krouting *routing)

This function seems to be ised in v4l2_subdev_link_validate() only,
let's make it static for now.

> +{
> +	int ret;
> +
> +	routing->which = state ? V4L2_SUBDEV_FORMAT_TRY : V4L2_SUBDEV_FORMAT_ACTIVE;

I think we could simplify this if we mandate subdev drivers to embed an
instance of v4l2_subdev_state for the active state. We could then drop
the .get_routing() operation. We could actually drop the .get_fmt()
operation too, but that would be a long term goal. As .get_routing() is
new, I'd rather not introduce it, and push drivers that need routing
support to use v4l2_subdev_state.

> +	routing->routes = NULL;
> +	routing->num_routes = 0;
> +
> +	ret = v4l2_subdev_call(sd, pad, get_routing, state, routing);
> +	if (ret == 0)
> +		return 0;
> +	if (ret != -ENOSPC)
> +		return ret;
> +
> +	routing->routes = kvmalloc_array(routing->num_routes,
> +					 sizeof(*routing->routes), GFP_KERNEL);
> +	if (!routing->routes)
> +		return -ENOMEM;
> +
> +	ret = v4l2_subdev_call(sd, pad, get_routing, state, routing);
> +	if (ret) {
> +		kvfree(routing->routes);
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(v4l2_subdev_get_routing);
> +
> +void v4l2_subdev_free_routing(struct v4l2_subdev_krouting *routing)
> +{
> +	kvfree(routing->routes);
> +	routing->routes = NULL;
> +	routing->num_routes = 0;
> +}
> +EXPORT_SYMBOL_GPL(v4l2_subdev_free_routing);
> +
> +int v4l2_subdev_cpy_routing(struct v4l2_subdev_krouting *dst,
> +			    const struct v4l2_subdev_krouting *src)
> +{
> +	if (dst->num_routes < src->num_routes) {
> +		dst->num_routes = src->num_routes;
> +		return -ENOSPC;
> +	}
> +
> +	memcpy(dst->routes, src->routes,
> +	       src->num_routes * sizeof(*src->routes));
> +	dst->num_routes = src->num_routes;
> +	dst->which = src->which;
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(v4l2_subdev_cpy_routing);

These two functions could also be made internal if we mandate usage of
v4l2_subdev_state.

> +
> +int v4l2_subdev_dup_routing(struct v4l2_subdev_krouting *dst,
> +			    const struct v4l2_subdev_krouting *src)
> +{
> +	v4l2_subdev_free_routing(dst);
> +
> +	if (src->num_routes == 0) {
> +		dst->which = src->which;
> +		return 0;
> +	}
> +
> +	dst->routes = kvmalloc_array(src->num_routes, sizeof(*src->routes),
> +				     GFP_KERNEL);
> +	if (!dst->routes)
> +		return -ENOMEM;
> +
> +	memcpy(dst->routes, src->routes,
> +	       src->num_routes * sizeof(*src->routes));
> +	dst->num_routes = src->num_routes;
> +	dst->which = src->which;
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(v4l2_subdev_dup_routing);
> +
> +bool v4l2_subdev_has_route(struct v4l2_subdev_krouting *routing,

The first argument can be const.

> +			   unsigned int pad0, unsigned int pad1)
> +{
> +	unsigned int i;
> +
> +	for (i = 0; i < routing->num_routes; ++i) {
> +		struct v4l2_subdev_route *route = &routing->routes[i];
> +
> +		if (!(route->flags & V4L2_SUBDEV_ROUTE_FL_ACTIVE))
> +			continue;
> +
> +		if ((route->sink_pad == pad0 && route->source_pad == pad1) ||
> +		    (route->source_pad == pad0 && route->sink_pad == pad1))
> +			return true;
> +	}
> +
> +	return false;
> +}
> +EXPORT_SYMBOL_GPL(v4l2_subdev_has_route);
> +
>  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 1cf91372d3cf..87f6bb78bbe9 100644
> --- a/include/media/v4l2-subdev.h
> +++ b/include/media/v4l2-subdev.h
> @@ -1248,4 +1248,73 @@ extern const struct v4l2_subdev_ops v4l2_subdev_call_wrappers;
>  void v4l2_subdev_notify_event(struct v4l2_subdev *sd,
>  			      const struct v4l2_event *ev);
>  
> +/**
> + * v4l2_subdev_get_routing() - Get routing from a subdevice
> + *
> + * @sd: The subdev from which to get the routing
> + * @state: Pointer to &struct v4l2_subdev_state
> + * @routing: Pointer to the target &struct v4l2_subdev_krouting
> + *
> + * Get a copy of the subdevice's routing table.
> + *
> + * Must be freed with v4l2_subdev_free_routing after use.
> + */
> +int v4l2_subdev_get_routing(struct v4l2_subdev *sd,
> +			    struct v4l2_subdev_state *state,
> +			    struct v4l2_subdev_krouting *routing);
> +
> +/**
> + * v4l2_subdev_free_routing() - Free the routing

Maybe "routing table" (here and where applicable) ? Up to you.

> + *
> + * @routing: The routing to be freed
> + *
> + * Frees the routing data in @routing.
> + */
> +void v4l2_subdev_free_routing(struct v4l2_subdev_krouting *routing);
> +
> +/**
> + * v4l2_subdev_cpy_routing() - Copy the routing
> + *
> + * @dst: The destination routing
> + * @src: The source routing
> + *
> + * Copies routing from @src to @dst without allocating space. If @dst does not
> + * have enough space, set dst->num_routes to the required number of routes, and
> + * return -ENOSPC.
> + *
> + * Can be used in subdevice's v4l2_subdev_pad_ops.get_routing() callback.
> + */
> +int v4l2_subdev_cpy_routing(struct v4l2_subdev_krouting *dst,
> +			    const struct v4l2_subdev_krouting *src);
> +
> +/**
> + * v4l2_subdev_dup_routing() - Duplicate the routing
> + *
> + * @dst: The destination routing
> + * @src: The source routing
> + *
> + * Makes a duplicate of the routing from @src to @dst by allocating enough
> + * memory and making a copy of the routing.
> + *
> + * Can be used in subdevice's v4l2_subdev_pad_ops.set_routing() callback
> + * to store the given routing.
> + *
> + * Must be freed with v4l2_subdev_free_routing after use.
> + */
> +int v4l2_subdev_dup_routing(struct v4l2_subdev_krouting *dst,
> +			    const struct v4l2_subdev_krouting *src);
> +
> +/**
> + * v4l2_subdev_has_route() - Check if there is a route between two pads

s/a route/an active route/

> + *
> + * @routing: The subdevice's routing
> + * @pad0: First pad
> + * @pad1: Second pad
> + *
> + * Returns whether there is a route between @pad0 and @pad1 of the same

Same here. Maybe we want to also mention "a direct route", as the
function doesn't return true when given pads B and C when there are
direct routes from A to B and A to C.

> + * subdevice according to the given routing.
> + */
> +bool v4l2_subdev_has_route(struct v4l2_subdev_krouting *routing,
> +			   unsigned int pad0, unsigned int pad1);
> +
>  #endif

-- 
Regards,

Laurent Pinchart