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: <YbM7xkTazM76CVvD@smile.fi.intel.com>
Date:   Fri, 10 Dec 2021 13:36:38 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Sergey Shtylyov <s.shtylyov@....ru>
Cc:     Damien Le Moal <damien.lemoal@...nsource.wdc.com>,
        linux-ide@...r.kernel.org, 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 02:19:52PM +0300, Sergey Shtylyov wrote:
> On 12/10/21 1:46 PM, 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;
> >>> 	return ret;
> >>
> >>    My unmerged patch (https://marc.info/?l=linux-kernel&m=163623041902285) does this
> >> but returns -EINVAL instead.
> >>
> >>> Otherwise, I do not think that removing the "if (!irq)" hunk is safe. no ?
> >>
> >>    Of course it isn't...
> > 
> > It's unsubstantiated statement. The vIRQ 0 shouldn't be returned by any of
> > those API calls.
> 
>    We do _not_ know what needs to be fixed, that's the problem, and that's why the WARN()
> is there...

So, have you seen this warning (being reported) related to libahci_platform?
If no, what we are discussing about then? The workaround is redundant and
no need to have a dead code in the driver, really.

> > If it is the case, go and fix them, no need to workaround
> > in each of the callers.
> 
>    There's a need to work around as long as IRQ0 ican be returned, otherwise
>    we get partly functioning or non-functioning drivers...

You get them unfunctioning anyways and you get the big WARN() even before this
patch.


-- 
With Best Regards,
Andy Shevchenko