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: <5322dafd-86ad-a293-6005-29384cb96cc8@omp.ru>
Date:   Sat, 11 Dec 2021 13:25:20 +0300
From:   Sergey Shtylyov <s.shtylyov@....ru>
To:     Damien Le Moal <damien.lemoal@...nsource.wdc.com>,
        Sergey Shtylyov <s.shtylyov@....ru>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        <linux-ide@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC:     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

Hello!

On 11.12.2021 2:45, Damien Le Moal 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.
> 
> Thinking more about this, shouldn't this change go into platform_get_irq()
> instead of platform_get_irq_optional() ?

    Why? platform_get_irq() currently just calls platform_get_irq_optional()...

> The way I see it, I think that the intended behavior for
> platform_get_irq_optional() is:
> 1) If have IRQ, return it, always > 0
> 2) If no IRQ, return 0

    That does include the IRQ0 case, right?

> 3) If error, return < 0
> no ?

   I completely agree, I (after thinking a bit) have no issues with that...

> And for platform_get_irq(), case (2) becomes an error.
> Is this the intended semantic ?

    I don't see how it's different from the current behavior. But we can do 
that as well, I just don't see whether it's really better...

> I am really not sure here as the functions kdoc description and the code do not
> match. Which one is correct ?

    It seems both are wrong. :-)

[...]

MBR, Sergey