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

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Date:	Wed, 31 Oct 2012 09:25:41 -0600
From:	Stephen Warren <swarren@...dotorg.org>
To:	Alex Courbot <acourbot@...dia.com>
CC:	Grant Likely <grant.likely@...retlab.ca>,
	Linus Walleij <linus.walleij@...aro.org>,
	devicetree-discuss@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: How about a gpio_get(device *, char *) function?

On 10/31/2012 03:04 AM, Alex Courbot wrote:
> Hi,
> 
> Would anyone be opposed to having a gpio_get() function that works similarly 
> to e.g. regulator_get() and clk_get()?

One major stumbling block is that with device tree, each individual
binding gets to decide on the specific naming of the propert{y,ies} that
define the GPIO(s) for the device, and so there's no way to provide a
generic implementation of that function.

Related, I've always wished that DT nodes looked like:

device {
    reg = <...>;
    compatible = <...>;
    resources {
        pwms = <...>;
        regulators = <...>;
        clocks = <...>;
        gpios = <...>;
        other-devices = <...>; /* for custom API dependencies */
    };
    config {
        /* device-specific properties */
    };
    child-busses {
        0 = { ... };
        1 = { ... };
    };
};

... specifically so that all resource allocation, and perhaps even child
bus enumeration, could be completely standardized in the DT/device core.
This could also feed into deferred probe, which could then be purely
implemented inside the DT/driver core. However, that'd require something
incompatible like "device tree 2.0"
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