linux-kernel - Re: How about a gpio_get(device *, char *) function?

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Message-ID: <CACRpkdaUJKs7zx=JWRUb+0Qz2dQU=R5KUK+CoM+nLCgHL99AFA@mail.gmail.com>
Date:	Wed, 7 Nov 2012 22:28:01 +0100
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Stephen Warren <swarren@...dotorg.org>
Cc:	Alex Courbot <acourbot@...dia.com>,
	Grant Likely <grant.likely@...retlab.ca>,
	devicetree-discuss@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: How about a gpio_get(device *, char *) function?

On Mon, Nov 5, 2012 at 6:35 PM, Stephen Warren <swarren@...dotorg.org> wrote:
> [Me]
>> gpio_get() should get an abstract handle just like clk_get() or
>> regulator_get(), not a fixed numeral.
>
> I don't really see why the return type of gpio_get() influences whether
> it can be implemented or not.

It doesn't influence that, but I want to follow the opaqueness design
pattern from irq descriptors and struct clk.

> With board files, some "gpio map" table would simply contain the same
> int GPIO ID value the table as is used anywhere else already. With DT,
> the same xlate function would translate from DT GPIO-chip-relative
> IDs/specifiers into the global number space in the same way that we do
> today via other APIs.

Yes, this part I buy into, just want to see how we can move forward
from there. The coplete nightmare is to introduce something into DT
that nails down a global GPIO numberspace... but I think that is not
the case atleast.

> If the GPIO subsystem were reworked as you propose, this API could be
> reworked in exactly the same way, or if implemented after the rework, it
> would return whatever handle type was in use at the time.

Yes, I just think we should return an opaque struct from day 1, so
just a little, little bit more to shield us.

Yours,
Linus Walleij
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