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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Date:   Sat, 11 Dec 2021 08:45:51 +0900
From:   Damien Le Moal <damien.lemoal@...nsource.wdc.com>
To:     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

On 2021/12/10 17:59, Sergey Shtylyov wrote:
> On 12/10/21 1:49 AM, 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() ?

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
3) If error, return < 0
no ?

And for platform_get_irq(), case (2) becomes an error.
Is this the intended semantic ?
I am really not sure here as the functions kdoc description and the code do not
match. Which one is correct ?

> 
>> Otherwise, I do not think that removing the "if (!irq)" hunk is safe. no ?
> 
>    Of course it isn't...
> 
>>> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> [...]
> 
> MBR, Sergey


-- 
Damien Le Moal
Western Digital Research