linux-kernel - Re: [PATCH v3 1/1] pinctrl: add Intel BayTrail GPIO/pinctrl support

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Date:	Thu, 17 Apr 2014 11:47:54 -0500
From:	Timur Tabi <timur@...eaurora.org>
To:	Mathias Nyman <mathias.nyman@...ux.intel.com>
CC:	Linus <linus.walleij@...aro.org>,
	Grant Likely <grant.likely@...retlab.ca>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 1/1] pinctrl: add Intel BayTrail GPIO/pinctrl support

On 04/15/2014 05:01 AM, Mathias Nyman wrote:
>>
>> This device will only be used on an ACPI system, right?  And isn't ACPI
>> supposed to hide all the pinctrl programming from the OS?  I thought
>> that was the whole point behind ACPI and the reason why ARM64 isn't
>> going to use device trees.
>>
>
> This was my starting point as well, and the driver was initially
> submitted as a GPIO driver. But Linus W. suggested pinctrl instead, and
> as he's the maintainer of both those subsystem I trust his judgment.

Do you think, for an ACPI pinctrl driver, that we will need to specify 
any function groups?  When I look at the ASL that configures GPIOs, I 
see only lines like this:

GpioIo (Exclusive, PullDefault, , , , "\\GIO0") {0x1D, 0x1E}

This tells me that ACPI will never use any of the names that are 
defined.  I see that .get_function_name is called on my ACPI system, but 
I don't see where it is used.

The reason I ask is because I would like to make a "generic" ACPI 
pinctrl/gpio driver that doesn't specify any pin groups.  So if we use 
the same pinctrl/gpio hardware on multiple SOCs, the only thing that the 
driver needs from ACPI is the number of pins.

-- 
Sent by an employee of the Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the
Code Aurora Forum, hosted by the Linux Foundation.
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