linux-kernel - Re: [PATCH v1 4/4] leds: no longer use unnamed gpios

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Date:	Thu, 8 Jan 2015 14:12:49 -0800
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	Rob Herring <robherring2@...il.com>
Cc:	Olliver Schinagl <oliver@...inagl.nl>,
	Olliver Schinagl <oliver+list@...inagl.nl>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	Alexandre Courbot <gnurou@...il.com>,
	Bryan Wu <cooloney@...il.com>,
	Richard Purdie <rpurdie@...ys.net>,
	Robin Gong <b38343@...escale.com>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Aaron Lu <aaron.lu@...el.com>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	Grant Likely <grant.likely@...aro.org>,
	Wolfram Sang <wsa@...-dreams.de>,
	Alexander Shiyan <shc_work@...l.ru>,
	Jingoo Han <jg1.han@...sung.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
	"linux-input@...r.kernel.org" <linux-input@...r.kernel.org>,
	linux-leds@...r.kernel.org
Subject: Re: [PATCH v1 4/4] leds: no longer use unnamed gpios

On Thu, Jan 08, 2015 at 08:40:20AM -0600, Rob Herring wrote:
> On Thu, Jan 8, 2015 at 2:45 AM, Olliver Schinagl <oliver@...inagl.nl> wrote:
> > Hey Dmitry,
> >
> >
> > On 08-01-15 00:55, Dmitry Torokhov wrote:
> >>
> >> On Wed, Jan 07, 2015 at 10:08:42AM +0100, Olliver Schinagl wrote:
> >>>
> >>> From: Olliver Schinagl <oliver@...inagl.nl>
> >>>
> >>> The gpio document says we should not use unnamed bindings for gpios.
> >>> This patch uses the 'led-' prefix to the gpios and updates code and
> >>> documents. Because the devm_get_gpiod_from_child() falls back to using
> >>> old-style unnamed gpios, we can update the code first, and update
> >>> dts files as time allows.
> 
> [...]
> 
> >>> --- a/drivers/leds/leds-gpio.c
> >>> +++ b/drivers/leds/leds-gpio.c
> >>> @@ -184,7 +184,7 @@ static struct gpio_leds_priv *gpio_leds_create(struct
> >>> platform_device *pdev)
> >>>                 struct gpio_led led = {};
> >>>                 const char *state = NULL;
> >>>   -             led.gpiod = devm_get_gpiod_from_child(dev, NULL, child);
> >>> +               led.gpiod = devm_get_gpiod_from_child(dev, "led", child);
> >>
> >> Would not this break existing boards using old bindings? You need to
> >> handle both cases: if you can't located "led-gpios" then you will have to
> >> try just "gpios".
> >
> > Very true. I was rather even hoping we could update all bindings, I don't
> > mind going through the available dts files to fix them ... But need to know
> > that that's the proper way to go before doing the work ;)
> 
> That will not work. You cannot make changes that require a new dtb
> with a new kernel. This would also break for the other way around
> (i.e. a new dtb and old kernel).
> 
> You would have to search for both led-gpios and gpios. I'm not sure if
> we can do that generically for all GPIOs. If you had a node with both
> "blah-gpios" and "gpios", it would break. I would hope there are no
> such cases like that. We also now have to consider how ACPI identifies
> GPIOs and whether this makes sense.

I think only the driver itself can know about such "legacy" mappings and
make a decision.

Thanks.

-- 
Dmitry
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