linux-kernel - Re: [PATCH 4/5] pci: handled return value of platform_get

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Message-ID: <871rpwhsnd.fsf@nanos.tec.linutronix.de>
Date:   Fri, 13 Mar 2020 22:05:58 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Bjorn Helgaas <helgaas@...nel.org>,
        Marc Gonzalez <marc.w.gonzalez@...e.fr>
Cc:     Aman Sharma <amanharitsh123@...il.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Andrew Murray <amurray@...goodpenguin.co.uk>,
        Linus Walleij <linus.walleij@...aro.org>,
        Ryder Lee <ryder.lee@...iatek.com>,
        Karthikeyan Mitran <m.karthikeyan@...iveil.co.in>,
        Hou Zhiqiang <Zhiqiang.Hou@....com>,
        Mans Rullgard <mans@...sr.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        linux-pci@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-mediatek@...ts.infradead.org,
        Marc Zyngier <maz@...nel.org>
Subject: Re: [PATCH 4/5] pci: handled return value of platform_get_irq correctly

Bjorn,

Bjorn Helgaas <helgaas@...nel.org> writes:
> On Thu, Mar 12, 2020 at 10:53:06AM +0100, Marc Gonzalez wrote:
>> Last time around, my understanding was that, going forward,
>> the best solution was:
>> 
>> 	virq = platform_get_irq(...)
>> 	if (virq <= 0)
>> 		return virq ? : -ENODEV;
>> 
>> i.e. map 0 to -ENODEV, pass other errors as-is, remove the dev_err
>> 
>> @Bjorn/Lorenzo did you have a change of heart?
>
> Yes.  In 10006651 (Oct 20, 2017), I thought:
>
>   irq = platform_get_irq(pdev, 0);
>   if (irq <= 0)
>     return -ENODEV;
>
> was fine.  In 11066455 (Aug 7, 2019), I said I thought I was wrong and
> that:
>
>   platform_get_irq() is a generic interface and we have to be able to
>   interpret return values consistently.  The overwhelming consensus
>   among platform_get_irq() callers is to treat "irq < 0" as an error,
>   and I think we should follow suit.
>   ...
>   I think the best pattern is:
>
>     irq = platform_get_irq(pdev, i);
>     if (irq < 0)
>       return irq;

Careful. 0 is not a valid interrupt.

Thanks,

        tglx