linux-kernel - Re: [PATCH 1/3] dt-bindings: gpio: sunxi：create a DT header for Allwinner pin controller

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Message-ID: <20200729130637.5md3tr6zg7s4wrmh@gilmour.lan>
Date:   Wed, 29 Jul 2020 15:06:37 +0200
From:   Maxime Ripard <maxime@...no.tech>
To:     Samuel Holland <samuel@...lland.org>
Cc:     Frank Lee <frank@...winnertech.com>, robh+dt@...nel.org,
        wens@...e.org, tiny.windzz@...il.com, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 1/3] dt-bindings: gpio: sunxi：create a DT header for Allwinner pin controller

Hi,

On Sat, Jul 25, 2020 at 02:18:39PM -0500, Samuel Holland wrote:
> On 7/17/20 11:07 AM, Maxime Ripard wrote:
> > Hi!
> > 
> > On Wed, Jul 15, 2020 at 07:54:12PM +0800, Frank Lee wrote:
> >> From: Yangtao Li <frank@...winnertech.com>
> >>
> >> The sunxi gpio binding defines a few custom cells for its gpio specifier.
> >> Provide bank name for those.
> >>
> >> Signed-off-by: Yangtao Li <frank@...winnertech.com>
> > 
> > Thanks for working on this, I wanted to do it at some point but it kept
> > getting pushed further into my todo list.
> > 
> >> ---
> >>  include/dt-bindings/gpio/sunxi-gpio.h | 29 +++++++++++++++++++++++++++
> >>  1 file changed, 29 insertions(+)
> >>  create mode 100644 include/dt-bindings/gpio/sunxi-gpio.h
> >>
> >> diff --git a/include/dt-bindings/gpio/sunxi-gpio.h b/include/dt-bindings/gpio/sunxi-gpio.h
> >> new file mode 100644
> >> index 000000000000..c692b4360da6
> >> --- /dev/null
> >> +++ b/include/dt-bindings/gpio/sunxi-gpio.h
> > 
> > So generally we've been using the compatible name as the file name. You
> > should follow that convention too, and since it was added with the A10,
> > using the A10 compatible.
> > 
> >> @@ -0,0 +1,29 @@
> >> +/* SPDX-License-Identifier: GPL-2.0 */
> >> +/*
> >> + * GPIO definitions for Allwinner SoCs
> >> + *
> >> + * Copyright (C) 2020 Yangtao Li <frank@...winnertech.com>
> >> + */
> >> +
> >> +#ifndef _DT_BINDINGS_SUNXI_GPIO_H
> >> +#define _DT_BINDINGS_SUNXI_GPIO_H
> >> +
> >> +#include <dt-bindings/gpio/gpio.h>
> >> +
> >> +/* pio */
> >> +#define PA	0
> >> +#define PB	1
> >> +#define PC	2
> >> +#define PD	3
> >> +#define PE	4
> >> +#define PF	5
> >> +#define PG	6
> >> +#define PH	7
> >> +#define PI	8
> >> +
> >> +/* r-pio */
> >> +#define PL	0
> >> +#define PM	1
> >> +#define PN	2
> >> +
> >> +#endif /* _DT_BINDINGS_SUNXI_GPIO_H */
> > 
> > Maybe we can go one step further and use a macro to have something like
> > PIN(A, 12) ?
> 
> Since we have separate cells for the bank and pin, I don't think it would be
> appropriate to have a single macro generating both.

Yeah, but it's "just" an encoding issue though, it's not a major concern
if it makes our life easier.

> And I'm not sure what the benefit of the macro would be, if all it
> does is forward its arguments. Are you concerned that P[A-M] could
> conflict with something else in the device tree?

There's indeed a bunch of names that are fairly generic and could be
conflicting with others (PD for power domain is the first one that comes
to my mind). Using a prefix would make the GPIO descriptors pretty long,
so it wasn't ideal either. A macro makes it readable without increasing
too much the risks of conflicts

Maxime

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