> And, what I meant in the previous thread was that the check in the > given patch wasn't "enough", i.e. it needs more careful checks > considering the boundary crossing. That is, you can't simply compare > appl_ptr vs old_appl_ptr as a single condition for the backward move. Indeed, that's why I tried to avoid any checks on pointers :-) > For example, check snd_pcm_playback_avail() and co. That contains a > couple of more condition checks and corrections due to the possible > boundary crossing. (Here, runtime->boundary may differ depending on > 32 or 64bit context.) > > The actual implementation of the backward move check would be slightly > different from those, but I hope you get my idea. I think I do but not sure how to precisely deal with the boundary wrap-around. The only suggestion I have at this point would be to compare the 'avail' space before and after the appl_ptr changes in pcm_lib_apply_appl_ptr(). If the 'avail' space grows as a result of user-space changes, that indicates a rewind (both for capture and playback), doesn't it? A tentative solution is shared here: https://github.com/thesofproject/linux/pull/3207
