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

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Message-ID: <CA+V-a8s+dWMwL6zQnWwFAa15sMgPGYrW+GZ=WhSW1tPxgpLOqA@mail.gmail.com>
Date:   Tue, 24 May 2022 10:06:46 +0100
From:   "Lad, Prabhakar" <prabhakar.csengg@...il.com>
To:     Linus Walleij <linus.walleij@...aro.org>
Cc:     Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>,
        Marc Zyngier <maz@...nel.org>,
        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>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        linux-tegra <linux-tegra@...r.kernel.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>,
        Linux-Renesas <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

Hi Linus,

Thank you for the feedback.

On Tue, May 24, 2022 at 9:54 AM Linus Walleij <linus.walleij@...aro.org> wrote:
>
> 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.
>
Agreed, I had a discussion with Marc on v3 series [0].

[0] https://patchwork.kernel.org/project/linux-renesas-soc/patch/20220511183210.5248-4-prabhakar.mahadev-lad.rj@bp.renesas.com/

Cheers,
Prabhakar