Re: [PATCH] m68k: atari: Make Atari ROM port I/O write macros return void

[Guenter Roeck]

On 5/20/22 07:32, Geert Uytterhoeven wrote:
> The macros implementing Atari ROM port I/O writes do not cast away their
> output, unlike similar implementations for other I/O buses.
> When they are combined using conditional expressions in the definitions of
> outb() and friends, this triggers sparse warnings like:
>
>      drivers/net/appletalk/cops.c:382:17: error: incompatible types in conditional expression (different base types):
>      drivers/net/appletalk/cops.c:382:17:    unsigned char
>      drivers/net/appletalk/cops.c:382:17:    void
>
> Fix this by adding casts to "void".
>
> Reported-by: kernel test robot <lkp@xxxxxxxxx>
> Reported-by: Guenter Roeck <linux@xxxxxxxxxxxx>
> Signed-off-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>

Reviewed-by: Guenter Roeck <linux@xxxxxxxxxxxx>

> ---
> Survived m68k/allmodconfig.
> To be queued in the m68k tree for v5.19.
>
> Removing the casts instead causes issues with functions propagating void
> return values (return expression in void function), which BTW sparse
> complains about, too.

We live and learn. I didn't even know that this was valid syntax.
I thought it might be easier to just fix that code, but coccinelle
reports that there are hundreds of places in the kernel where this
is done. Outch.

Guenter