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:   Fri, 10 Dec 2021 22:35:41 +0300
From:   Sergei Shtylyov <sergei.shtylyov@...il.com>
To:     Sergey Shtylyov <s.shtylyov@....ru>,
        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 10:30 PM, Sergey Shtylyov 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.
>>>
>>>    I have clearly explained to you what I'm working around there. If that wasn't clear
>>> enough, I don't want to continue this talk anymore. Good luck with your patch (not this
>>> one).
>>
>> Good luck with yours, not the one that touches platform_get_irq_optional() though!
> 
>    Mmh, I'm not touching it any way that would break what your patch was trying to do,
> unless you've re-thopught that. It also shoudn't matter whose patch gets merged 1st 
> other than some small adaptation).

   BTW, looking at [1], this comment is wrong:

+ * Return: non-zero IRQ number on success, negative error number on failure.

It doesn't mention 0 which you return from this function.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ed7027fdf4ec41ed6df6814956dc11860232a9d5

MBR, Sergey