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

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Date:   Thu, 19 Mar 2020 09:47:47 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     Marc Gonzalez <marc.w.gonzalez@...e.fr>,
        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 Helgaas <helgaas@...nel.org> writes:
> On Wed, Mar 18, 2020 at 02:42:48PM +0100, Thomas Gleixner wrote:
>> Bjorn Helgaas <helgaas@...nel.org> writes:
>> > On Fri, Mar 13, 2020 at 04:56:42PM -0500, Bjorn Helgaas wrote:
>> >> On Fri, Mar 13, 2020 at 10:05:58PM +0100, Thomas Gleixner wrote:
>> >> > >   I think the best pattern is:
>> >> > >
>> >> > >     irq = platform_get_irq(pdev, i);
>> >> > >     if (irq < 0)
>> >> > >       return irq;
>> >> > 
>> >> > Careful. 0 is not a valid interrupt.
>> >> 
>> >> Should callers of platform_get_irq() check for a 0 return value?
>> >> About 900 of them do not.
>> 
>> I don't know what I was looking at.
>> 
>> platform_get_irq() does the right thing already, so checking for irq < 0
>> is sufficient.
>> 
>> Sorry for the confusion!
>
> Thanks, I was indeed confused!  Maybe we could reduce future confusion
> by strengthening the comments slightly, e.g.,
>
>   - * Return: IRQ number on success, negative error number on failure.
>   + * Return: non-zero IRQ number on success, negative error number on failure.
>
> I don't want to push my luck, but it's pretty hard to prove that
> platform_get_irq() never returns 0.  What would you think of something
> like the following?

No objections from my side.