linux-kernel - Re: [PATCH v5 3/5] gpio: gpiolib: Allow free() callback to be overridden

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Date:   Tue, 24 May 2022 10:54:39 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>,
        Marc Zyngier <maz@...nel.org>
Cc:     Geert Uytterhoeven <geert+renesas@...der.be>,
        Thomas Gleixner <tglx@...utronix.de>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Bartosz Golaszewski <brgl@...ev.pl>,
        Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Andy Gross <agross@...nel.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        linux-gpio@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Prabhakar <prabhakar.csengg@...il.com>,
        linux-renesas-soc@...r.kernel.org,
        Phil Edworthy <phil.edworthy@...esas.com>,
        Biju Das <biju.das.jz@...renesas.com>
Subject: Re: [PATCH v5 3/5] gpio: gpiolib: Allow free() callback to be overridden

On Mon, May 23, 2022 at 7:43 PM Lad Prabhakar
<prabhakar.mahadev-lad.rj@...renesas.com> wrote:

> Allow free() callback to be overridden from irq_domain_ops for
> hierarchical chips.
>
> This allows drivers to free up resources which are allocated during
> child_to_parent_hwirq()/populate_parent_alloc_arg() callbacks.
>
> On Renesas RZ/G2L platform a bitmap is maintained for TINT slots, a slot
> is allocated in child_to_parent_hwirq() callback which is freed up in free
> callback hence this override.
>
> Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> Reviewed-by: Geert Uytterhoeven <geert+renesas@...der.be>

So that function today looks like this:

static void gpiochip_hierarchy_setup_domain_ops(struct irq_domain_ops *ops)
{
        ops->activate = gpiochip_irq_domain_activate;
        ops->deactivate = gpiochip_irq_domain_deactivate;
        ops->alloc = gpiochip_hierarchy_irq_domain_alloc;
        ops->free = irq_domain_free_irqs_common;

        /*
         * We only allow overriding the translate() function for
         * hierarchical chips, and this should only be done if the user
         * really need something other than 1:1 translation.
         */
        if (!ops->translate)
                ops->translate = gpiochip_hierarchy_irq_domain_translate;
}

(...)
-       ops->free = irq_domain_free_irqs_common;
(...)
> +       if (!ops->free)
> +               ops->free = irq_domain_free_irqs_common;

Marc Z is working on cleaning up the way that gpiolib is (ab)using
irqchips. We definitely need his ACK if we do things like this.
This doesn't look like one of the big offenders to me, but I want
to make sure we don't create new problems while Marc is trying
to solve the old ones.

Yours,
Linus Walleij