linux-kernel - Re: [PATCH v3 4/5] gpio: gpiolib: Add ngirq member to struct gpio_irq

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Date:   Wed, 18 May 2022 19:36:28 +0100
From:   "Lad, Prabhakar" <prabhakar.csengg@...il.com>
To:     Linus Walleij <linus.walleij@...aro.org>
Cc:     Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Thomas Gleixner <tglx@...utronix.de>,
        Marc Zyngier <maz@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Bartosz Golaszewski <brgl@...ev.pl>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        Phil Edworthy <phil.edworthy@...esas.com>,
        Biju Das <biju.das.jz@...renesas.com>
Subject: Re: [PATCH v3 4/5] gpio: gpiolib: Add ngirq member to struct gpio_irq_chip

Hi Linus,

Thank you for the review.

On Fri, May 13, 2022 at 9:47 PM Linus Walleij <linus.walleij@...aro.org> wrote:
>
> On Wed, May 11, 2022 at 8:32 PM Lad Prabhakar
> <prabhakar.mahadev-lad.rj@...renesas.com> wrote:
>
> > Supported GPIO IRQs by the chip is not always equal to the number of GPIO
> > pins. For example on Renesas RZ/G2L SoC where it has GPIO0-122 pins but at
> > a give point a maximum of only 32 GPIO pins can be used as IRQ lines in
> > the IRQC domain.
> >
> > This patch adds ngirq member to struct gpio_irq_chip and passes this as a
> > size to irq_domain_create_hierarchy()/irq_domain_create_simple() if it is
> > being set in the driver otherwise fallbacks to using ngpio.
> >
> > Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
>
> As Geert says, I think you can just use .valid_mask for this,
> what do you say?
>
I don't think Geert is suggesting that. The .valid_mask option is one
time setting but what I need is something dynamic i.e. out of 392 GPIO
pins any 32 can be used as an interrupt pin. Also with this patch we
also save on memory [0].

[0] https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/kernel/irq/irqdomain.c?h=next-20220518#n153

Cheers,
Prabhakar