On Tue, 11 Apr 2023 19:23:17 +0200, Jaroslav Kysela wrote: > > On 11. 04. 23 18:50, Oswald Buddenhagen wrote: > > >> If we allow modification of the PCM buffer, I think that we should: > >> > >> - Do not modify the buffer for drivers already working with the > >> appl_ptr data (end position) only. > >> > > i suppose that should be detected by the drain callback being set up? > > Yes, but it would be probably better to add a default silencing > callback with a warning to notify authors of drivers to review and > eventually correct the behavior. > > >> - Handle the situation with the large buffer; it may make sense > >> to change the "wait" operation from the end-of-period interrupt to time > >> scheduler and stop the drain more early when the end-of-valid data condition > >> is fulfilled. > >> > > i don't understand what you're asking for. > > Use jiffies/timeout instead waiting to the interrupt. In this case, > the stop may be called earlier (in the middle of period). In this case > the silenced area may be much smaller. Does this difference matter so much? I guess you're concerned about the performance, right? This sounds a bit too complex just for the simple purpose... > >> - Increase the protocol version. > >> > >> But as I wrote, I would make those extensions configurable > >> (SNDRV_PCM_HW_PARAMS_DRAIN_ALLOW_SILENCE). It can be turned on by default. > >> > > i have no clue what would be involved in doing that. to me that sounds > > like overkill (solving a non-issue), and goes waaaay beyond what i > > expected to invest into this issue (really, i just wanted to verify that > > the emu10k1 fixes work, and accidentally discovered that there is a > > mid-layer issue that affects user space, as the pyalsaaudio lib i'm > > using doesn't handle it). > > OK. I don't think that it's a pyalsaudio job to resolve the issue with > the minimal transfer chunk / period (which you set / know before the > transfer is initiated). I'm thinking whether we need to change anything in the kernel side for this at all. Can't it be changed rather in alsa-lib side instead? Takashi
