Re: [PATCH/RFC v3 06/19] video: display: OF support

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

Hi Philipp,

On Wednesday 21 August 2013 11:10:12 Philipp Zabel wrote:
> Am Mittwoch, den 21.08.2013, 03:02 +0200 schrieb Laurent Pinchart:
> > On Tuesday 13 August 2013 16:37:07 Philipp Zabel wrote:
> > > Hi Laurent,
> > > 
> > > thanks for this update. I'm very happy about the move to the display
> > > entity model, given that the i.MX6 IPU has both drm/display and
> > > v4l2/capture ports> in a single device - this will allow to use a
> > > unified device tree binding scheme.
> > 
> > Thanks for the support :-)
> > 
> > > I'm still trying to see how this all fits together, so far I have only
> > > one comment, below.
> > > 
> > > Am Freitag, den 09.08.2013, 19:14 +0200 schrieb Laurent Pinchart:
> > > [...]
> > > 
> > > > +static int display_of_parse_dt(struct display_entity_notifier
> > > > *notifier,
> > > > +			       struct list_head *entities,
> > > > +			       struct device_node *node)
> > > > +{
> > > > +	struct display_entity_of *entity;
> > > > +	struct device_node *remote;
> > > > +	struct device_node *ep = NULL;
> > > > +	struct device_node *next;
> > > > +	unsigned int num_entities = 0;
> > > > +	int ret = 0;
> > > > +
> > > > +	/* Walk the device tree and build a list of nodes. */
> > > > +	dev_dbg(notifier->dev, "parsing node %s\n", node->full_name);
> > > > +
> > > > +	while (1) {
> > > > +		next = display_of_get_next_endpoint(node, ep);
> > > > +		if (next == NULL)
> > > > +			break;
> > > > +
> > > > +		of_node_put(ep);
> > > > +		ep = next;
> > > > +
> > > > +		dev_dbg(notifier->dev, "handling endpoint %s\n", ep->full_name);
> > > > +
> > > > +		remote = display_of_get_remote_port_parent(ep);
> > > > +		if (remote == NULL)
> > > > +			continue;
> > > > +
> > > > +		/* Skip entities that we have already processed. */
> > > > +		if (display_of_find_entity(entities, remote) || remote == node) {
> > > > +			dev_dbg(notifier->dev,
> > > > +				"entity %s already in list, skipping\n",
> > > > +				remote->full_name);
> > > > +			continue;
> > > > +		}
> > > 
> > > device tree nodes with status = "disabled" should be skipped here:
> > >                 if (!of_device_is_available(remote)) {
> > >                         dev_dbg(notifier->dev,
> > >                                 "entity %s is disabled, skipping\n",
> > >                                 remote->full_name);
> > >                         continue;
> > >                 }
> > > 
> > > Otherwise the completion notification will never be delivered if there
> > > are any disabled entities in the graph.
> > 
> > That's a good point, but if a device is disabled, why would it be in the
> > DT graph in the first place ? Do you have a use case for this ?
> 
> This is mostly about separate encoders inside the SoC, which are always
> present but not useful unless the board designer connected something to
> the external pads. Those might be contained in the SoC .dtsi but have
> status = "disabled" set for board device tree writers' convenience.
> My use case would be the LVDS encoder bridge or the Synopsys Designware
> HDMI TX on i.MX6.

My point was that, if a DT node is disabled, it should not be linked in a CDF 
graph in DT. However, I agree that it's easier to express the in-SoC links in 
the .dtsi files, so you've got a point. I'll integrate the change in v4.

-- 
Regards,

Laurent Pinchart