linux-kernel - Re: [PATCH v3 1/3] gpio: vf610: add support to DT 'ngpios' property

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Date: Thu, 18 Jan 2024 11:03:44 +0200
From: Andy Shevchenko <andy.shevchenko@...il.com>
To: Hector Palacios <hector.palacios@...i.com>
Cc: linus.walleij@...aro.org, brgl@...ev.pl, robh+dt@...nel.org, 
	krzysztof.kozlowski+dt@...aro.org, andy@...nel.org, conor+dt@...nel.org, 
	shawnguo@...nel.org, s.hauer@...gutronix.de, kernel@...gutronix.de, 
	festevam@...il.com, linux-imx@....com, stefan@...er.ch, 
	linux-gpio@...r.kernel.org, devicetree@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/3] gpio: vf610: add support to DT 'ngpios' property

On Thu, Jan 18, 2024 at 10:25 AM Hector Palacios
<hector.palacios@...i.com> wrote:
> On 1/17/24 21:51, Andy Shevchenko wrote:
> >> Some SoCs, such as i.MX93, don't have all 32 pins available
> >> per port. Allow optional generic 'ngpios' property to be
> >> specified from the device tree and default to
> >> VF610_GPIO_PER_PORT (32) if the property does not exist.

..

> >> +       ret = device_property_read_u32(dev, "ngpios", &ngpios);
> >> +       if (ret || ngpios > VF610_GPIO_PER_PORT)
> >> +               gc->ngpio = VF610_GPIO_PER_PORT;
> >> +       else
> >> +               gc->ngpio = (u16)ngpios;
> >
> > This property is being read by the GPIOLIB core. Why do you need to repeat this?
>
> My apologies; I had not seen this.
> I'll use gpiochip_get_ngpios() on the next iteration.

But still why?
https://elixir.bootlin.com/linux/latest/source/drivers/gpio/gpiolib.c#L867

It's called for every driver.

Maybe it's needed to be refactored to allow fallbacks? Then can the
GPIO MMIO case also be updated?

-- 
With Best Regards,
Andy Shevchenko