linux-kernel - Re: [PATCH v4 09/14] irqchip: Provide platform_device to of_irq_init_cb

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Date:   Wed, 20 Oct 2021 16:28:41 +0100
From:   Marc Zyngier <maz@...nel.org>
To:     Florian Fainelli <f.fainelli@...il.com>
Cc:     Rob Herring <robh@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Ray Jui <rjui@...adcom.com>,
        Scott Branden <sbranden@...adcom.com>,
        "maintainer:BROADCOM BCM281XX/BCM11XXX/BCM216XX ARM ARCHITE..." 
        <bcm-kernel-feedback-list@...adcom.com>,
        Russell King <linux@...linux.org.uk>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Frank Rowand <frowand.list@...il.com>,
        "moderated list:ARM SUB-ARCHITECTURES" 
        <linux-arm-kernel@...ts.infradead.org>,
        "open list:MIPS" <linux-mips@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE" 
        <devicetree@...r.kernel.org>
Subject: Re: [PATCH v4 09/14] irqchip: Provide platform_device to of_irq_init_cb_t

On Wed, 20 Oct 2021 16:14:07 +0100,
Florian Fainelli <f.fainelli@...il.com> wrote:
> 
> 
> 
> On 10/20/2021 1:24 AM, Marc Zyngier wrote:
> > On Tue, 19 Oct 2021 23:23:52 +0100,
> > Rob Herring <robh@...nel.org> wrote:
> >> 
> >>   On Tue, Oct 19, 2021 at 4:43 PM Marc Zyngier <maz@...nel.org> wrote:
> >>> 
> >>> diff --git a/include/linux/irqchip.h b/include/linux/irqchip.h
> >>> index ccf32758ea85..146a9d80a6a2 100644
> >>> --- a/include/linux/irqchip.h
> >>> +++ b/include/linux/irqchip.h
> >>> @@ -33,7 +33,15 @@ extern int platform_irqchip_probe(struct platform_device *pdev);
> >>>   #define IRQCHIP_PLATFORM_DRIVER_BEGIN(drv_name) \
> >>>   static const struct of_device_id drv_name##_irqchip_match_table[] = {
> >>> 
> >>> -#define IRQCHIP_MATCH(compat, fn) { .compatible = compat, .data = fn },
> >>> +/* Undefined on purpose */
> >>> +int typecheck_irq_init_cb(struct device_node *, struct device_node *,
> >>> +                         struct platform_device *);
> >>> +
> >>> +#define typecheck_irq_init_cb(fn)                                      \
> >>> +       __typecheck(typecheck_irq_init_cb, fn) ? fn : fn
> >> 
> >> That's nice! Shouldn't it also be used for IRQCHIP_DECLARE?
> > 
> > Absolutely. And enabling this shows that changing of_irq_init_cb_t
> > breaks *all users* of IRQCHIP_DECLARE(). Not an acceptable outcome
> > when we're at -rc5. >
> > Why can't the relevant drivers use of_find_device_by_node() instead?
> > That would allow us to keep the status-quo on of_irq_init_cb_t.
> 
> Rob had suggested several solutions, including using
> of_find_device_by_node(), however updating of_irq_init_cb_t was
> indicated to be the better way. I had intentionally not updated
> IRQCHIP_DECLARE() because it would ignore the 3rd argument we passed
> to it (platform_device *) so I thought.

In general, conflicting prototype always lead to the compiler
legitimately screwing something up, and you are left with a pile of
steaming crap to debug.

So *no* to that sort of trick.

> If I am spinning a v6 using of_find_device_by_node() would that be
> acceptable to you?

That'd be much better.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.