Re: [PATCH v2 6/7] ASoC: cs42l43: Refactor to use for_each_set_bit()

On Thu, Jan 25, 2024 at 09:11:44PM +0200, Andy Shevchenko wrote:

On Thu, Jan 25, 2024 at 12:31 PM Charles Keepax ckeepax@opensource.cirrus.com wrote: Adding nslots parameter is a good idea, but I still think the code can be refactored better (have you checked the code generation, btw? I believe my version would be better or not worse).

...

•   for_each_set_bit(slot, &mask, BITS_PER_TYPE(mask)) {
  

•           if (i == nslots) {
  

•                   dev_warn(priv->dev, "Too many channels in TDM mask: %lx\n",
  

•                            mask);
                    return;
  

•           }
  
  

•           slots[i++] = slot;
    }
  

   i = 0;
   for_each_set_bit(slot, &mask, CS42L43_ASP_MAX_CHANNELS)
           slots[i++] = slot;

   if (hweight_long(mask) >= CS42L43_ASP_MAX_CHANNELS)
           dev_warn(priv->dev, "Too many channels in TDM mask\n");

The code is simpler and behaviour is not changed.

I don't think this works, the limit here is on the number of channels not on the position of those channels. The last parameter of for_each_set_bits appears to measure against the bit position not the number of set bits. So for example 0xFC000000 would be a valid 6 channel mask, but would result in no slot positions being set in the above code.

Thanks, Charles