On 03/02/2023 18:02, Jaroslav Kysela wrote:
Thank you for your suggestion, but I think that the *whole* code for !get_time_info in update_audio_tstamp() should be recoded. The calling of ns_to_timespec64() is not enough to handle the boundary wraps in a decent range (tenths years for 24x7 operation)
Yes, indeed. My ambition was unnecessarily short.
and the bellow code is dangerous for 32-bit apps / system:
if (crossed_boundary) { snd_BUG_ON(crossed_boundary != 1); runtime->hw_ptr_wrap += runtime->boundary; }
I don't understand why?
I would probably propose to have just hw_ptr_wrap +1 counter (we can reconstruct the frame position back by multiplication and do range check later),
Would that really help that much? It would extend the total possible duration but perhaps ~1523287 years(below) is sufficient.
remove snd_BUG_ON
Again, why?
and improve the timespec64 calculation.
The calculation should be split to two parts (tv_sec / tv_nsec):
- calculate seconds: (frames / rate)
- calculate the remainder (ns): ((frames % rate) * NSEC_PER_SEC) / rate
With 64-bit integer range, we should go up to (for 384000Hz rate):
2**64 / 384000 / 3600 / 24 / 365 = ~1523287 years
Yes indeed. How about this?
static inline void snd_pcm_lib_frames_to_timespec64(u64 frames, unsigned int rate, struct timespec64 *audio_tstamp) { u32 remainder; audio_tstamp->tv_sec = div_u64_rem(frames, rate, &remainder); audio_tstamp->tv_nsec = div_u64(mul_u32_u32(remainder, NSEC_PER_SEC), rate); }
Alan.