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

[Arnd Bergmann <arnd@arndb.de>]

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.

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?

      Arnd