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: <YbOVmGw7ys6U51z3@smile.fi.intel.com>
Date:   Fri, 10 Dec 2021 19:59:52 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Sergei Shtylyov <sergei.shtylyov@...il.com>
Cc:     Sergey Shtylyov <s.shtylyov@....ru>,
        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 08:15:43PM +0300, Sergei Shtylyov wrote:
> On 12/10/21 2:36 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?
> 
>    No (as if you need to really see this while it's obvious from the code review).
> 
> > If no, what we are discussing about then? The workaround is redundant and
> 
>    I don't know. :-) Your arguments so far seem bogus (sorry! :-))...

It seems you haven't got them at all. The problems of platform_get_irq() et al
shouldn't be worked around in the callers.

> > no need to have a dead code in the driver, really.
> 
>   "Jazz isn't dead, it just smells funny". :-)
> 
> >>> 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
> 
>    The drivers would be broken in not quite obvious ways. With IRQ0 check, they just
> don't probe anymore. See the explanation of the IRQ0 check (in the drivers) in my
> previous mail...
> 
> > and you get the big WARN() even before this patch.
> 
>    As if that was enough...
>    The IRQ0 problem exists for at least 15 (if not 20) years...

-- 
With Best Regards,
Andy Shevchenko