linux-kernel - Re: [PATCH v3] leds: implement OpenFirmare GPIO LED driver

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Date:	Wed, 16 Jul 2008 22:15:31 -0600
From:	Grant Likely <grant.likely@...retlab.ca>
To:	Trent Piepho <tpiepho@...escale.com>
Cc:	Anton Vorontsov <avorontsov@...mvista.com>,
	Richard Purdie <rpurdie@...ys.net>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	Kumar Gala <galak@...nel.crashing.org>,
	linux-kernel@...r.kernel.org, linuxppc-dev@...abs.org
Subject: Re: [PATCH v3] leds: implement OpenFirmare GPIO LED driver

On Wed, Jul 16, 2008 at 04:18:52PM -0700, Trent Piepho wrote:
> On Tue, 15 Jul 2008, Anton Vorontsov wrote:
> > Despite leds-gpio and leds-openfirmware-gpio similar purposes, there
> > is not much code can be shared between the two drivers (both are mostly
> > driver bindings anyway).
> 
> Why can't this driver use the existing gpio-led driver?  Basically, do
> something like this:
> 
> of_gpio_leds_probe(...)
> {
>  	gpio = of_get_gpio(np, 0);
>  	label = of_get_property(np, "label", NULL);
> 
>  	struct gpio_led led = {
>  		.name = label,
>  		.gpio = gpio,
>  	};
> 
>  	pdev = platform_device_register_simple("leds-gpio", 0, NULL, 0);
>  	platform_device_add_data(pdev, &led, sizeof(led));
> }

Ugh; that means registering *2* 'struct device' with the kernel instead of
one.  One as a platform device and one as an of_platform device.
It's bad enough that the LED scheme we're using for OF bindings has a
separate registration for every single LED.

Now that it comes to it, I worry that this driver takes the wrong
approach.  The number of resources dedicated per LED in this driver
seems pretty loony to me (one of_platform device per LED).  The fact
that the binding specifies one node per LED makes of_platform not a very
efficient solution.

I think it would be better to have a module that scans the device tree
for LED nodes and registers a single leds-gpio platform device for the
whole lot.

Thoughts?

g.
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