Re: [PATCH v2] ARM: s3c: irq-s3c24xx: Fix return value check for s3c24xx_init_intc()

[Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>]

On 26/10/2021 17:10, Arnd Bergmann wrote:
> On Wed, Sep 1, 2021 at 2:35 PM Jackie Liu <liu.yun@linux.dev> wrote:
> 
>> +               /* For platform based machines, neither ERR nor NULL can happen here.
>> +                * The s3c24xx_handle_irq() will be set as IRQ handler iff this succeeds:
>> +                *
>> +                *    s3c_intc[0] = s3c24xx_init_intc()
>> +                *
>> +                * If this fails, the next calls to s3c24xx_init_intc() won't be executed.
>> +                *
>> +                * For DT machine, s3c_init_intc_of() could set the IRQ handler without
>> +                * setting s3c_intc[0] only if it was called with num_ctrl=0. There is no
>> +                * such code path, so again the s3c_intc[0] will have a valid pointer if
>> +                * set_handle_irq() is called.
>> +                *
>> +                * Therefore in s3c24xx_handle_irq(), the s3c_intc[0] is always something.
>> +                */
>> +               if (s3c24xx_handle_intc(s3c_intc[0], regs, 0))
>> +                       continue;
>>
>> -               if (s3c_intc[2])
>> +               if (!IS_ERR_OR_NULL(s3c_intc[2]))
>>                         if (s3c24xx_handle_intc(s3c_intc[2], regs, 64))
>>                                 continue;
> 
> I just saw this in the pull request. I'm taking the pull request since
> it's a bugfix and
> the resulting code is technically correct, but I'd point out that this
> is particularly
> ugly. Any use of IS_ERR_OR_NULL() essentially means we have a misdefined
> interface, and it's clear that this is one of them.

Yes, that's the case.

> 
> Nothing actually uses the return code of s3c24xx_init_intc(), so returning
> NULL on error there and changing all the checks to that would be a much
> more straightforward solution.
> 
> Any chance you could send a follow-up to do that?

I can work on this but you know this is a legacy platform and none of us
can test it?


Best regards,
Krzysztof