linux-kernel - Re: [PATCH 1/3] gpio / ACPI: add ACPI support

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Message-ID: <5097AD9D.7060808@linux.intel.com>
Date:	Mon, 05 Nov 2012 14:14:21 +0200
From:	Mathias Nyman <mathias.nyman@...ux.intel.com>
To:	Linus Walleij <linus.walleij@...aro.org>
CC:	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	linux-kernel@...r.kernel.org, lenb@...nel.org,
	rafael.j.wysocki@...el.com, broonie@...nsource.wolfsonmicro.com,
	grant.likely@...retlab.ca, khali@...ux-fr.org, ben-linux@...ff.org,
	w.sang@...gutronix.de, linux-acpi@...r.kernel.org
Subject: Re: [PATCH 1/3] gpio / ACPI: add ACPI support

On 11/05/2012 01:53 PM, Linus Walleij wrote:
> On Sat, Nov 3, 2012 at 8:46 AM, Mika Westerberg
> <mika.westerberg@...ux.intel.com>  wrote:
>
>> +/**
>> + * acpi_get_gpio() - Translate ACPI GPIO pin to GPIO number usable with GPIO API
>> + * @path:      ACPI GPIO controller full path name, (e.g. "\\_SB.GPO1")
>> + * @pin:       ACPI GPIO pin number (0-based, controller-relative)
>> + *
>> + * Returns GPIO number to use with Linux generic GPIO API, or errno error value
>> + */
>
> So by just looking at that we can see that this is yet another
> instance of papering
> over the fact that the Linux GPIO numbers are global to the kernel and not
> per-chip, as would be preferred.

Yes, it is. ACPI5 GPIO resources are numbered per-chip. This is just a 
way for device drivers to find the corresponding Linux GPIO.

per-chip based numbering sounds saner, but this deals with what we 
currently have.

>
> Can you please contribute to the parallel discussion on how to get rid of
> the global GPIO numberspace, thread named:
> "How about a gpio_get(device *, char *) function?"

I'll take a look at it, (and see if I got anything of value to add)

-Mathias
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