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: <9e6b2e9a-e958-0c14-6570-135607041978@omp.ru>
Date:   Fri, 10 Dec 2021 14:19:52 +0300
From:   Sergey Shtylyov <s.shtylyov@....ru>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
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 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...

> 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...

MBR, Sergey