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

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

Hi Kieran,

On Tue, Mar 17, 2020 at 12:33:07PM +0000, Kieran Bingham wrote:
> On 16/03/2020 21:47, Laurent Pinchart wrote:
> > On Mon, Mar 16, 2020 at 10:40:12PM +0100, Niklas Söderlund wrote:
> >> On 2020-03-15 14:55:11 +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>
> >>
> >> I tested this on R-Car CSI-2 and ADV748x without any regressions. As 
> >> Jacopo already pointed out it's similar to what have been tried before 
> 
> This was the patch that I had believed was accepted, but ended up stuck
> in Sakari's tree:
> 
> https://git.linuxtv.org/sailus/media_tree.git/commit/?h=fwnode-const&id=35c32d99b2c3f5086b911ec817926de9b7bc3b41
> 
> (it's already a little bit-rotted though)

Yes, I noticed that. I don't mind dropping this patch if you rebase
yours, as long as we merge a fix :-)

> >> and have the potential problem for new transmitters registering multiple 
> >> endpoints (like ADV748x) being used together with older receivers who 
> >> register a single device node in v4l-async. But this do not introduce 
> 
> So if an 'old' receiver wants to use the 'new' features, it must upgrade
> to endpoint matching.
> 
> I think that's fine.

Yes that's the idea. It will however not have to upgrade all the subdev
drivers it uses at the same time.

> >> any regressions and is a good first step to move everything to endpoint 
> >> matching.
> >>
> >> Tested-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
> >>
> >> Maybe a info message should be logged if a match is made between 
> >> endpoint and node? It would make it easy to spot if one needs to debug a 
> >> miss match and would be a clear message one driver should be moved to 
> >> endpoint matching. Maybe adding such a log message would count as a 
> >> regression for some.
> > 
> > WARN("FIX YOUR DRIVER TO USE ENDPOINT MATCHING") ? :-)
> 
> Indeed, a notification that they need to update their matching would be
> useful in that scenario.
> 
> I believe we need to move forward with this somehow, as we have Xilinx
> trying to use MAX9286 with Xilinx drivers, (endpoint matching subdev
> with dev node matching receiver) and Renesas trying to use non-endpoint
> subdevices against an endpoint matched RCar-VIN ...?
> 
> > Jokes aside, something a bit less harsh such as "Matching endpoint with
> > device node, consider fixing driver %s to use endpoints" wouldn't be a
> > bad idea.
> 
> Yes, Is there anything else we can do? Even if we 'started' converting
> other receivers to match on endpoints, it would take time - so I think
> an intermediate stage like this is still very useful.
> 
> Of course this patch also lets us push the updates back to those who
> care about those drivers too ...

Exactly :-)

> >>> ---
> >>> 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");
> >>> +
> >>> +	if (sd_fwnode_is_ep == asd_fwnode_is_ep)
> >>> +		return false;
> 
> Ok, so this looks like a good safety check for edge cases which would
> potentially have got through in my version.
> 
> >>> +
> >>> +	/*
> >>> +	 * 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);
> 
> It seems in my implementation these got leaked too :-)
> 
> I'm sold. This one is better than the old version I had.
> 
> Hopefully we can get this moving so that we can progress towards
> endpoint matching throughout next.
> 
> (Ideally with a warning to convert non-endpoint matching drivers...)
> 
> Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>

Thank you. I'll add a warning and agree with Sakari on the best method
to check if a node is an endpoint node, and will then resubmit.

> >>> +
> >>> +	return dev_fwnode == other_fwnode;
> >>>  }
> >>>  
> >>>  static bool match_custom(struct v4l2_subdev *sd, struct v4l2_async_subdev *asd)

-- 
Regards,

Laurent Pinchart