Re: [PATCH v1 1/2] ata: libahci_platform: Get rid of dup message when IRQ can't be retrieved

Sergey Shtylyov
2021-12-11T10:13:59Z

On 10.12.2021 22:35, Sergei 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.

Also, your commit log is wrong in the description of how to handle the result:

<<
Now:
ret = platform_get_irq_optional(...);
if (ret != -ENXIO)
return ret; // respect deferred probe
if (ret > 0)
...we get an IRQ...
>>

The (ret != -ENXIO) check also succeeds on the (positive) IRQ #s, so the
following code becomes unreachable. :-/

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

MBR, Sergey