Re: [PATCH] media: v4l2-async: Accept endpoints and devices for fwnode matching

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

Hi Sakari,

On Wed, Mar 18, 2020 at 01:04:32AM +0200, Laurent Pinchart wrote:
> On Tue, Mar 17, 2020 at 02:44:56PM +0200, Sakari Ailus wrote:
> > On Sun, Mar 15, 2020 at 02:55:11PM +0200, Laurent Pinchart wrote:
> > > fwnode matching was designed to match on nodes corresponding to a
> > > device. Some drivers, however, needed to match on endpoints, and have
> > > passed endpoint fwnodes to v4l2-async. This works when both the subdev
> > > and the notifier use the same fwnode types (endpoint or device), but
> > > makes drivers that use different types incompatible.
> > > 
> > > Fix this by extending the fwnode match to handle fwnodes of different
> > > types. When the types (deduced from the node name) are different,
> > > retrieve the device fwnode for the side that provides an endpoint
> > > fwnode, and compare it with the device fwnode provided by the other
> > > side. This allows interoperability between all drivers, regardless of
> > > which type of fwnode they use for matching.
> > > 
> > > Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
> > > ---
> > > This has been compile-tested only. Prabhakar, could you check if it
> > > fixes your issue ?
> > > 
> > >  drivers/media/v4l2-core/v4l2-async.c | 42 +++++++++++++++++++++++++++-
> > >  1 file changed, 41 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/media/v4l2-core/v4l2-async.c b/drivers/media/v4l2-core/v4l2-async.c
> > > index 8bde33c21ce4..995e5464cba7 100644
> > > --- a/drivers/media/v4l2-core/v4l2-async.c
> > > +++ b/drivers/media/v4l2-core/v4l2-async.c
> > > @@ -71,7 +71,47 @@ static bool match_devname(struct v4l2_subdev *sd,
> > >  
> > >  static bool match_fwnode(struct v4l2_subdev *sd, struct v4l2_async_subdev *asd)
> > >  {
> > > -	return sd->fwnode == asd->match.fwnode;
> > > +	struct fwnode_handle *other_fwnode;
> > > +	struct fwnode_handle *dev_fwnode;
> > > +	bool asd_fwnode_is_ep;
> > > +	bool sd_fwnode_is_ep;
> > > +	const char *name;
> > > +
> > > +	/*
> > > +	 * Both the subdev and the async subdev can provide either an endpoint
> > > +	 * fwnode or a device fwnode. Start with the simple case of direct
> > > +	 * fwnode matching.
> > > +	 */
> > > +	if (sd->fwnode == asd->match.fwnode)
> > > +		return true;
> > > +
> > > +	/*
> > > +	 * Otherwise, check if the sd fwnode and the asd fwnode refer to an
> > > +	 * endpoint or a device. If they're of the same type, there's no match.
> > > +	 */
> > > +	name = fwnode_get_name(sd->fwnode);
> > > +	sd_fwnode_is_ep = name && strstarts(name, "endpoint");
> > > +	name = fwnode_get_name(asd->match.fwnode);
> > > +	asd_fwnode_is_ep = name && strstarts(name, "endpoint");
> > 
> > Apart from the fact that you're parsing graph node names here, this looks
> > good.

And why is that an issue btw ? the ACPI fwnode ops seem to provide a
.get_name() operation, would it return the ACPI bus ID here ?

> > How about checking instead that calling
> > fwnode_graph_get_remote_endpoint(fwnode_graph_get_remote_endpoint()) yields
> > the same node? That would ensure you're dealing with endpoint nodes without
> > explicitly parsing the graph in any way.
> 
> Would it be simpler to check for the presence of an endpoint property ?
> 
> > Just remember to drop the references.
> > 
> > > +
> > > +	if (sd_fwnode_is_ep == asd_fwnode_is_ep)
> > > +		return false;
> > > +
> > > +	/*
> > > +	 * The sd and asd fwnodes are of different types. Get the device fwnode
> > > +	 * parent of the endpoint fwnode, and compare it with the other fwnode.
> > > +	 */
> > > +	if (sd_fwnode_is_ep) {
> > > +		dev_fwnode = fwnode_graph_get_port_parent(sd->fwnode);
> > > +		other_fwnode = asd->match.fwnode;
> > > +	} else {
> > > +		dev_fwnode = fwnode_graph_get_port_parent(asd->match.fwnode);
> > > +		other_fwnode = sd->fwnode;
> > > +	}
> > > +
> > > +	fwnode_handle_put(dev_fwnode);
> > > +
> > > +	return dev_fwnode == other_fwnode;
> > >  }
> > >  
> > >  static bool match_custom(struct v4l2_subdev *sd, struct v4l2_async_subdev *asd)

-- 
Regards,

Laurent Pinchart