Re: [PATCH] ati-vga: increment mm_index in ati_mm_read/write

[Gerd Hoffmann <kraxel@redhat.com>]

On Wed, Jun 03, 2020 at 08:05:50PM +0530, P J P wrote:
> +-- On Wed, 3 Jun 2020, Gerd Hoffmann wrote --+
> | Hmm, why modify mm_index?  Shouldn't we just check it is non-zero
> | before calling ati_mm_read/ati_mm_write?
> 
>   if (s->regs.mm_index & BIT(31)) {
>      ...
>   } else {

} else if (s->regs.mm_index > 3) {

>      ati_mm_write(s, s->regs.mm_index + addr - MM_DATA, data, size);
>   }
> 
> Exit condition for recursion is to set (mm_index & BIT(31)), so recursion 
> would continue even with non-zero values I think.

It's wrapped into a case switch for all the registers.  The code quoted
above is only entered for "addr >= MM_DATA && addr <= MM_DATA+3", so the
check should stop recursion.  A less strict "s->regs.mm_index > 0" may
recurse a few times but will not recurse endless either.

cheers,
  Gerd