On 2018-06-20 15:21:49 [+0200], Takashi Iwai wrote: > > usb_fill_int_urb() ensures that syncinterval is within the allowed range > > on HS/SS. The interval value seems to come from > > snd_usb_parse_datainterval() which is bInterval - 1 and only in the rage > > 1 … 4. So in order to keep the magic working I pass datainterval + 1. > > This needs more explanation. By this conversion, the interval > computation becomes really tricky. > > There are two interval calculations. The first one is > fp->datainterval and it's from snd_usb_parse_datainterval() as you > mentioned. And a tricky part is that fp->datainterval is 0 on > FULL_SPEED. Casually, fp->datainterval+1 will be translated to the > correct value since (0 + 1) == (1 << 0). > > OTOH, for the sync EP, it's taken from ep->syncinterval, which is set > in snd_usb_add_endpoint(). Luckily, again, ep->syncinterval + 1 works > for FULL_SPEED as well, as (1 + 1) == (1 << 1). Do you want me to add your additional explanation to the description? > thanks, > > Takashi Sebastian _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
