linux-kernel - Re: [PATCH 07/11] of/irq: Export of_irq

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Date:   Mon, 27 Sep 2021 15:09:10 -0500
From:   Rob Herring <robh+dt@...nel.org>
To:     Florian Fainelli <f.fainelli@...il.com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Russell King <linux@...linux.org.uk>,
        Ray Jui <rjui@...adcom.com>,
        Scott Branden <sbranden@...adcom.com>,
        "maintainer:BROADCOM BCM281XX/BCM11XXX/BCM216XX ARM ARCHITE..." 
        <bcm-kernel-feedback-list@...adcom.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        Rich Felker <dalias@...c.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Marc Zyngier <maz@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Mike Rapoport <rppt@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Arnd Bergmann <arnd@...db.de>,
        Guenter Roeck <linux@...ck-us.net>,
        Kefeng Wang <wangkefeng.wang@...wei.com>,
        Mark Rutland <mark.rutland@....com>,
        Andrey Konovalov <andreyknvl@...il.com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Valentin Schneider <valentin.schneider@....com>,
        Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        "moderated list:ARM PORT" <linux-arm-kernel@...ts.infradead.org>,
        "open list:SUPERH" <linux-sh@...r.kernel.org>,
        "open list:BROADCOM BMIPS MIPS ARCHITECTURE" 
        <linux-mips@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE" 
        <devicetree@...r.kernel.org>
Subject: Re: [PATCH 07/11] of/irq: Export of_irq_count to drivers

On Mon, Sep 27, 2021 at 2:49 PM Florian Fainelli <f.fainelli@...il.com> wrote:
>
> On 9/27/21 12:43 PM, Rob Herring wrote:
> > On Mon, Sep 27, 2021 at 2:28 PM Florian Fainelli <f.fainelli@...il.com> wrote:
> >>
> >> On 9/27/21 12:08 PM, Rob Herring wrote:
> >>> On Fri, Sep 24, 2021 at 12:07 PM Florian Fainelli <f.fainelli@...il.com> wrote:
> >>>>
> >>>> In order to build drivers/irqchip/irq-bcm7120-l2.c as a module, we will
> >>>> need to have of_irq_count() exported to modules.
> >>>>
> >>>> Signed-off-by: Florian Fainelli <f.fainelli@...il.com>
> >>>> ---
> >>>>  drivers/of/irq.c | 1 +
> >>>>  1 file changed, 1 insertion(+)
> >>>>
> >>>> diff --git a/drivers/of/irq.c b/drivers/of/irq.c
> >>>> index 352e14b007e7..949b9d1f8729 100644
> >>>> --- a/drivers/of/irq.c
> >>>> +++ b/drivers/of/irq.c
> >>>> @@ -440,6 +440,7 @@ int of_irq_count(struct device_node *dev)
> >>>>
> >>>>         return nr;
> >>>>  }
> >>>> +EXPORT_SYMBOL_GPL(of_irq_count);
> >>>
> >>> Please convert to use platform_irq_count() instead.
> >>
> >> That requires a platform_device to be passed to platform_irq_count(),
> >> will that work even when the drivers remain built into the kernel and
> >> get initialized early on?
> >
> > No, does your irqchip using this do both? Looks to me like it is
> > always a platform_device.
>
> On ARM/ARM64 not using GKI as well as MIPS, we would want the module to
> be built into the kernel image, however when using GKI that driver would
> become a module. How do you suggest reconciling both usages?

What's there to resolve? Every driver that works as a module can be
built-in. Is there something special about irqchip drivers?

The only issue I see here is platform_irqchip_probe() doesn't pass the
platform_device pointer to the irq_init_cb function. There's 3 ways to
fix that. Add a platform_device pointer to the init hook. That's a
global change though. That's the right thing to do IMO. Or you can use
of_find_device_by_node(). That's fairly expensive, but easy and
isolated. You could also set device_node.data pointer to the
platform_device, but ideally I'd like to get rid of that pointer as
it's hardly used.

Rob