Hi Sean, On 04.12.20 at 09:44, Sean Young wrote:
>> What about an extra check then to make sure that the period has not been >> truncated, >> e.g: >> >> value = DIV_ROUND_CLOSEST_ULL(state->period, scaler); >> >> /* dont accept a period that is too small or has been truncated */ >> if ((value < PERIOD_MIN) || >> (value != DIV_ROUND_CLOSEST_ULL(state->period, scaler))) >> return -EINVAL; > > Rather than doing another 64 bit division which is expensive (esp on 32 bit > kernels), you could assign to u64 and check: > > if (value < PERIOD || value > U32_MAX) > return -EINVAL; > Sound reasonable, I will adjust this. > > There was a problem where the carrier is incorrect for some IR hardware > which uses a carrier of 455kHz. With periods that small, rounding errors > do really matter and rounding down might cause problems. > > A policy of rounding down the carrier is not the right thing to do > for pwm-ir-tx, and such a change will probably break pwm-ir-tx in some > edge cases. > Thanks for this background information. Regards, Lino
