linux-kernel - Re: [PATCH] platform: finally disallow IRQ0 in platform_get

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Date:   Tue, 04 Jan 2022 11:13:43 +0000
From:   Marc Zyngier <maz@...nel.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Geert Uytterhoeven <geert@...ux-m68k.org>,
        Sergey Shtylyov <s.shtylyov@....ru>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] platform: finally disallow IRQ0 in platform_get_irq() and its ilk

On Tue, 04 Jan 2022 10:53:34 +0000,
Greg Kroah-Hartman <gregkh@...uxfoundation.org> wrote:
> 
> On Tue, Jan 04, 2022 at 10:48:00AM +0000, Marc Zyngier wrote:
> > On Tue, 04 Jan 2022 09:47:21 +0000,
> > Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
> > > 
> > > On Tue, Jan 4, 2022 at 10:26 AM Marc Zyngier <maz@...nel.org> wrote:
> > > > Geert recently mentioned that a few architectures (such as sh?) still
> > > > use IRQ0 as something valid in limited cases.
> > > 
> > > https://lore.kernel.org/all/CAMuHMdUg3=q7gyaVHP0XcYUOo3PQUUv8Hc8wp5faVQ+bTBpg4A@mail.gmail.com
> > > 
> > > TL;DR: Probably only smsc911x Ethernet on the AP-SH4A-3A and
> > > AP-SH4AD-0A boards, which should trigger the warning since v5.8.
> > > 
> > > > From my PoV, this patch is fine, but please be prepared to fix things
> > > > in a couple of years when someone decides to boot a recent kernel on
> > > > their pet dinosaur. With that in mind:
> > > >
> > > > Acked-by: Marc Zyngier <maz@...nel.org>
> > > 
> > > TBH, I don't see much point in this patch, as the WARN() has been
> > > there since a while, and the end goal is to return zero instead of
> > > -ENXIO for no interrupt, right?
> > 
> > I think the end-goal is to never return 0. Either we return a valid
> > interrupt number, or we return an error. It should be the
> > responsibility of the caller to decide what they want to do in the
> > error case.
> 
> As 0 still is a valid irq for some platforms (as mentioned above), then
> how is this ever going to be possible?

Fixing the offending platforms should be a pre-requisite. At least the
ones we know about.

Thanks,

	M.

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