linux-kernel - Re: [PATCH] GPIOLIB: add generic gpio_set

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Message-ID: <CAGsJ_4xq2kpVu2BXPkeeWaZYYN=r73_2V2eOnT5FA8dv43at5w@mail.gmail.com>
Date:	Tue, 9 Aug 2011 10:51:18 +0800
From:	Barry Song <21cnbao@...il.com>
To:	Rohit Vaswani <rvaswani@...eaurora.org>
Cc:	Kyungmin Park <kmpark@...radead.org>,
	Linus Walleij <linus.walleij@...ricsson.com>,
	linux-kernel@...r.kernel.org, workgroup.linux@....com,
	Grant Likely <grant.likely@...retlab.ca>,
	Paul Mundt <lethal@...ux-sh.org>,
	Barry Song <Baohua.Song@....com>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] GPIOLIB: add generic gpio_set_pull API

2011/8/9 Rohit Vaswani <rvaswani@...eaurora.org>:
> On 8/8/2011 3:57 PM, Kyungmin Park wrote:
>>
>> On Tue, Aug 9, 2011 at 3:24 AM, Grant Likely<grant.likely@...retlab.ca>
>>  wrote:
>>>
>>> On Mon, Aug 8, 2011 at 2:15 AM, Paul Mundt<lethal@...ux-sh.org>  wrote:
>>>>
>>>> On Sun, Aug 07, 2011 at 10:19:33PM -0700, Barry Song wrote:
>>>>>
>>>>> Now there are many different implementations for GPIO pull
>>>>> configuration, for
>>>>> example:
>>>>> s3c_gpio_setpull()
>>>>> tegra_pinmux_set_pullupdown()
>>>>> chipcHw_setPinPullup()
>>>>> gpio_pullup()
>>>>> s3c2410_gpio_pullup()
>>>>>
>>>>> This patch adds a new generic gpio_set_pull API so that all SoCs can
>>>>> have unified
>>>>> codes.
>>>>>
>>>>> Signed-off-by: Barry Song<Baohua.Song@....com>
>>>>
>>>> For arch/arm/mach-shmobile we also have gpio_pull_up() for board-g4evm.c
>>>> and gpio_pull_down() for board-mackerel.c. Both of these would benefit
>>>> from this sort of an API addition.
>>>
>>> I think I'm okay with this API change.  Linus, what say you?  How does
>>> this interact with your plans for pinctrl?
>>
>> If gpiolib accept the pullup control. gpiolib is better place to
>> control gpio config.
>> then remains are the gpio driver strength, and power down mode
>> control. powerdown pull-up/down, powerdown in/out at samsung gpios.
>
> If we add this API - the remaining gpio controls like drive strength and
> function select could also be added, which eats into the pinmux domain.
> Linus W. had a patch earlier which added an API for a gpio config to be
> specified through gpiolib. " gpio: add a custom configuration mechanism to
> gpiolib" which is sort of an extensible model of this API.

gpio_config() from Linus W. is an interface with multiple functions or
a function for multiple purpose. Its actions seem to be ambiguous,
then mean diffiicult to use or diffirent subsystems still result in
many differences after using it.

pullup/down/none is something very common and much frequently used to
all SoCs, i guess it can have individual, simple and direct API.

I don't oppose gpiolib cover more GPIO configurations, for example OC,
OD and powerdown. but we might keep APIs as simple and clear as
possible.

>
> Thanks,
> Rohit
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