linux-kernel - Re: [PATCH v1 1/2] ata: libahci_platform: Get rid of dup message when IRQ can't be retrieved

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Message-ID: <CAHp75VcdwozpUJVB17VmCDska7euYnx1VjZLnCaZ8DHG+_3vYg@mail.gmail.com>
Date:   Fri, 10 Dec 2021 10:47:41 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Damien Le Moal <damien.lemoal@...nsource.wdc.com>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        linux-ide@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Hans de Goede <hdegoede@...hat.com>,
        Jens Axboe <axboe@...nel.dk>
Subject: Re: [PATCH v1 1/2] ata: libahci_platform: Get rid of dup message when
 IRQ can't be retrieved

On Fri, Dec 10, 2021 at 4:47 AM Damien Le Moal
<damien.lemoal@...nsource.wdc.com> wrote:
> On 2021/12/09 23:59, Andy Shevchenko wrote:
> > platform_get_irq() will print a message when it fails.
> > No need to repeat this.
> >
> > While at it, drop redundant check for 0 as platform_get_irq() spills
> > out a big WARN() in such case.
>
> The reason you should be able to remove the "if (!irq)" test is that
> platform_get_irq() never returns 0. At least, that is what the function kdoc
> says. But looking at platform_get_irq_optional(), which is called by
> platform_get_irq(), the out label is:
>
>         WARN(ret == 0, "0 is an invalid IRQ number\n");
>         return ret;
>
> So 0 will be returned as-is. That is rather weird. That should be fixed to
> return -ENXIO:
>
>         if (WARN(ret == 0, "0 is an invalid IRQ number\n"))
>                 return -ENXIO;

No, this is wrong for the same reasons I explained to Sergey.
The problem is that this is _optional API and it has been misdesigned.
Replacing things like above will increase the mess.

>         return ret;
>
> Otherwise, I do not think that removing the "if (!irq)" hunk is safe. no ?

No. This is not a business of the caller to workaround implementation
details (bugs) of the core APIs.
If something goes wrong, then it's platform_get_irq() to blame, and
not the libahci_platform.

-- 
With Best Regards,
Andy Shevchenko