linux-kernel - Re: [PATCH v2] gpio: Add driver for TI TPIC2810

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Message-ID: <CAHp75VfTofe13JCcJmFq=yex7zRdmzTSMMSX8Tap5cBZ80rJ2Q@mail.gmail.com>
Date:	Wed, 10 Feb 2016 16:29:46 +0200
From:	Andy Shevchenko <andy.shevchenko@...il.com>
To:	Linus Walleij <linus.walleij@...aro.org>
Cc:	"Andrew F. Davis" <afd@...com>,
	"linux-leds@...r.kernel.org" <linux-leds@...r.kernel.org>,
	Richard Purdie <rpurdie@...ys.net>,
	Jacek Anaszewski <j.anaszewski@...sung.com>,
	Alexandre Courbot <gnurou@...il.com>,
	Javier Martinez Canillas <javier@...hile0.org>,
	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] gpio: Add driver for TI TPIC2810

On Wed, Feb 10, 2016 at 4:21 PM, Linus Walleij <linus.walleij@...aro.org> wrote:
> On Sun, Jan 31, 2016 at 11:52 PM, Andy Shevchenko
> <andy.shevchenko@...il.com> wrote:
>
>> It reminds me how 12 channel PWM chip is used on Intel Galileo Gen 2.
>> Half pins are PWM, the other half is GPIO used for discrete based pin
>> muxing and control. Nevertheless I think it's a userspace issue for
>> now, otherwise we have to provide some 'semi-virtual' way of
>> presenting pins as GPIO lines.
>
> That sounds like an MFD spawning a GPIO and a PWM cell.
> That it is called "a PWM chip" is no big deal, it should be
> modeled according to what it is, not what it claims to be.

Although I agree with model I barely imagine how in this case drivers
should access PWM chip registers in non-race way (take into account
that PWM itself is connected to i2c bus).

> (Which makes me wanna merge this present patch as a GPIO
> driver since it claims to be a LED driver but is a GPO.)
>
> See the ST Multipurpose Expander for an example
> drivers/mfd/stmpe.c
> drivers/gpio/gpio-stmpe.c
> drivers/input/keyboard/stmpe-keypad.c

I will look to the example later, thanks.

-- 
With Best Regards,
Andy Shevchenko