linux-kernel - Re: [PATCH 3/3] gpio: regmap: Support a custom ->to

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Message-ID: <7EciRXW2jHHdJoybh7lao4eux9khP3Sc@localhost>
Date:   Wed, 06 Jul 2022 21:53:36 +0100
From:   Aidan MacDonald <aidanmacdonald.0x0@...il.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Michael Walle <michael@...le.cc>,
        Bartosz Golaszewski <brgl@...ev.pl>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/3] gpio: regmap: Support a custom ->to_irq() hook

Andy Shevchenko <andy.shevchenko@...il.com> writes:

> On Tue, Jul 5, 2022 at 1:22 PM Aidan MacDonald
> <aidanmacdonald.0x0@...il.com> wrote:
>
> ...
>
>> Is that really better than simply using ->to_irq()?
>
> We have Intel PMIC drivers (that are in MFD) and they have respective
> GPIO drivers, none of them is using ->to_irq() and all of them provide
> IRQ functionality. Can it be taken as an example or is it something
> quite different to your hardware?

In the Intel PMICs the MFD irqchip has a single interrupt for all GPIOs.
The GPIO driver then has its own irqchip and it looks at other registers
to find out which GPIO interrupt fired. It's a typical cascaded setup.

In my case the MFD irqchip has one interrupt per GPIO. The GPIO driver
does not need its own irqchip; everything is handled by the MFD irqchip.
Existing examples include wm831x, wm8994, da9052, and tps6586x.