How much do we care about avoiding unnecessary 64-bit calculations in 32-bit applications?
I think I am going to have to submit another fix to pcm_rate:snd_pcm_rate_sync_hwptr0(). I'm not sure yet, but I think that the fix by /mahendran.kuppusamy@in.bosch.com/ can result in, at least, off-by-one errors in the calculated value. I have yet to determine whether the error is ever cumulative and the consequences.
My proposed fix includes (rate->slave_hw_ptr_wrap is u_int64_t):
+ if (rate->slave_hw_ptr_wrap) { + /* + * Restrict explicit 64-bit calculations to case where rate->slave_hw_ptr_wrap + * is non-zero, which will only happen in 32-bit environments. + */ + u_int64_t wrapped_slave_hw_ptr = slave_hw_ptr + rate->slave_hw_ptr_wrap; + new_hw_ptr = ((wrapped_slave_hw_ptr / slave_period_size) * period_size) % boundary; + slave_residual = wrapped_slave_hw_ptr % slave_period_size; + } else { + new_hw_ptr = (slave_hw_ptr / slave_period_size) * period_size; + slave_residual = slave_hw_ptr % slave_period_size; + }
so it only ever does 64-bit calculations if there has been a boundary wrap.
Is that optimization desirable (assuming my fix is necessary at all) or would it be better just to do 64-bit calculations all the time?