linux-kernel - Re: [PATCH v3] gpio: UniPhier: add driver for UniPhier GPIO controller

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Date:	Thu, 26 May 2016 11:06:48 +0200
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc:	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Alexandre Courbot <gnurou@...il.com>
Subject: Re: [PATCH v3] gpio: UniPhier: add driver for UniPhier GPIO controller

On Fri, May 20, 2016 at 6:30 AM, Masahiro Yamada
<yamada.masahiro@...ionext.com> wrote:

> So, I'd like to know the recommended driver coding style
> based on 4.7-rc1.

Sure, best is to look at other recently added drivers
I guess.

> Diving into the git-log so far, I came up the following list:
>
> [1] The "dev" member of gpiochip was renamed to "parent"

Yes.

> [2] The most recommended register function is now
>     devm_gpiochip_add_data()

Yes, saves some code.

> [3] Pass the driver private data to the
>     3rd argument of devm_gpiochip_add_data().

Yes.

> [4] Do not use container_of() to covert
>     from gpiochip to driver private data.
>     Instead, gpiochip_get_data() should be used.

Yes.

>     (I used of_mm_gpio_chip in v3,
>      but I needed to use container_of() to
>      convert from gpiochip to of_mm_gpio_chip.
>      I am wondering if you are happy with it or not.)

We will see when we look at the code ;)
I guess it is OK. The alternative is to use gpio-generic instead,
see commit 42178e2a1e42b480ada954750f248b53d3fb5940
"drivers/gpio: Switch gpio-mpc8xxx to use gpio-generic"
for an example of that approach.

> [5] gpiochip.owner is being deprecated.
>     So, platform drivers need not set
>      "gpiochip.owner =  THIS_MODULE".

Yes.

> Correct?

Yes.

> Is there anything else missing?

I advice to add a .get_direction() callback if possible and
also .set_single_ended() if the GPIO chip supports open
drain / open source in hardware.

Yours,
Linus Walleij