linux-kernel - Re: [PATCH 1/5] pci: handled return value of platform_get

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Date:   Thu, 12 Mar 2020 23:45:21 +0100
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     Aman Sharma <amanharitsh123@...il.com>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Andrew Murray <amurray@...goodpenguin.co.uk>,
        Ryder Lee <ryder.lee@...iatek.com>,
        Karthikeyan Mitran <m.karthikeyan@...iveil.co.in>,
        Hou Zhiqiang <Zhiqiang.Hou@....com>,
        Marc Gonzalez <marc.w.gonzalez@...e.fr>,
        Mans Rullgard <mans@...sr.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        linux-pci <linux-pci@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@...ts.infradead.org>,
        Marc Zyngier <maz@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 1/5] pci: handled return value of platform_get_irq correctly

On Thu, Mar 12, 2020 at 8:02 PM Bjorn Helgaas <helgaas@...nel.org> wrote:

> IIUC, in the link you mentioned, Linus T says that "dev->irq == 0"
> means we don't have a valid IRQ.  I think that makes sense, but I'm
> not sure it follows that 0 must be a sensical return value for
> platform_get_irq().  It seems to me that platform_get_irq() ought to
> return either a valid IRQ or an error, and the convention for errors
> is a negative errno.

OK I see your point.

I would be fine of the code is changed from:

if (irq <= 0)
  error;

To:

if (irq < 0)
   error retrieving IRQ

if (!irq)
   error driver requires a valid IRQ

To the driver (this one in specific) the IRQ is expected and
necessary and I think it holds for most PCI hosts.

Yours,
Linus Walleij