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SubjectRe: [PATCH 2/2] drm/rockchip: Convert the probe function to the generic drm_of_component_probe()
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Am Montag, 16. November 2015, 16:52:06 schrieb Liviu Dudau:
> On Mon, Nov 16, 2015 at 04:30:16PM +0000, Russell King - ARM Linux wrote:
> > I've tweaked your patch to make the above (buggy) change a little clearer.
> >
> > On Mon, Nov 16, 2015 at 02:44:53PM +0000, Liviu Dudau wrote:
> > > - for (i = 0;; i++) {
> > > - port = of_parse_phandle(np, "ports", i);
> > > - if (!port)
> > > - break;
> > > -
> > > - if (!of_device_is_available(port->parent)) {
> > > - of_node_put(port);
> > > - continue;
> > > - }
> > >
> > > - component_match_add(dev, &match, compare_of, port->parent);
> > > - of_node_put(port);
> > > - }
> > >
> > > -static int compare_of(struct device *dev, void *data)
> > > -{
> > > - struct device_node *np = data;
> > > -
> > > - return dev->of_node == np;
> > > -}
> >
> > The original above passes port->parent to component_match_add(). This
> > means 'np' in the above compare_of() function is 'port->parent'.
> >
> > This means the above comparison is effectively:
> > dev->of_node == port->parent
> >
> > The generic code instead does this:
> > component_match_add(dev, &match, compare_of, port);
> >
> > So what we get in the comparison function is 'port' rather than
> >
> > 'port->parent':
> > > +static int compare_port(struct device *dev, void *data)
> > >
> > > {
> > >
> > > + struct device_node *np = data;
> > > + return dev->parent->of_node == np;
> > > +}
> >
> > which means the comparison is:
> > dev->parent->of_node == port
> >
> > which is a different comparison from the above.
> >
> > You instead want this to be:
> > return dev->of_node == np->parent;
> >
> > Heiko, please test the above change to compare_port() - I think you'll
> > find that will fix your issue.
>
> Sorry, I admit I'm not very good at doing patches without being able
> to test them. :(
>
> Thanks for helping on this!

Russell's hint was correct. With the compare function changed like he pointed
out, I again get a working display with your patches :-)

So, thanks Russell for spotting this.


Heiko


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