linux-kernel - Re: [PATCH v3 3/9] gpio: 104-dio-48e: Migrate to the regmap-irq API

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Date:   Sun, 27 Nov 2022 17:00:40 -0500
From:   William Breathitt Gray <william.gray@...aro.org>
To:     Michael Walle <michael@...le.cc>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     linus.walleij@...aro.org, brgl@...ev.pl,
        linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org,
        broonie@...nel.org
Subject: Re: [PATCH v3 3/9] gpio: 104-dio-48e: Migrate to the regmap-irq API

On Sun, Nov 27, 2022 at 07:31:48PM +0100, Michael Walle wrote:
> Hi,
> 
> [sorry this mail was just delivered now, although it seems
> to be sent last Tuesday.]

Actually I just sent it today, but you're right that it seems to have a
date of last Tuesday, so I must have configured something wrong on my
end before I sent it (sorry).

> 
> Am 2022-11-22 11:29, schrieb William Breathitt Gray:
> > On Wed, Nov 23, 2022 at 05:01:53PM +0200, Andy Shevchenko wrote:
> > > On Tue, Nov 22, 2022 at 02:11:00AM -0500, William Breathitt Gray
> > > wrote:
> > > > +	/* Initialize device interrupt state */
> > > > +	err = regmap_read(map, DIO48E_DISABLE_INTERRUPT, &val);
> > > > +	if (err)
> > > > +		return err;
> > > 
> > > Use ->init_hw() callback for this.
> > 
> > In a subsequent patch 7/9 we remove direct gpio_chip registration in
> > favor of the i8255 library registration via gpio_regmap. It doesn't look
> > like gpio_regmap_register() sets the init_hw() callback.
> > 
> > Michael, do you see any issues if I introduce init_hw() to
> > gpio_regmap_config? Or do you think this IRQ initialization belongs
> > somewhere else?
> 
> Something like the following?
>   gpiochip->init_hw = config.irq_init_hw;
> 
> gpiochip doesn't seem to be the correct place, gpiochip_add_irqchip()
> is a noop for gpio-regmap, right? So using gpiochip_irqchip_init_hw()
> seems wrong.
> 
> Maybe make gpio-regmap call it on its own? But really we just connect
> the regmap-irq to the gpiochip irqdomain.

I think you're right, it feels strange to handle IRQ initialization via
the GPIO framework. Maybe somewhere in regmap_irq might be more
appropriate?

> What is the purpose of the
> .init_hw callback? I've looked at other drivers which use regmap-irq
> and they all seem to just initialize the hardware in their _probe().
> 
> -michael

I'm not opposed to initializing the hardware in _probe(), although I can
see merit in pushing that operation instead closer to the framework
where the initialization is actually relevant.

Andy, maybe you can shed some light about .init_hw; I think you
introduced it to gpiolib in commit 9411e3aaa6342.

William Breathitt Gray

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