Hi, On Mon, 2004-03-01 at 08:52, Clemens Ladisch wrote: > Manuel Jander wrote: > > AFAIK, it seems that when using a scatter gather buffer, not every > > period is located inside of a page. ... > > The problem is that a DMA transfer can not go accross 2 different pages. > > On Aureal hardware, even on contiguous buffers this causes all sort of > > odd problems. Each DMA chunk must be on the same page. > > ... > > That means that i would have to split each period that crosses a page > > boundary into 2 DMA chunks, with all the complications involved because > > of irregular sizes, offsets... ARghhh! > > Yes. Every driver using SG must do this. Look into bt87x.c or > via82xx.c for examples.
Well, i guess in that case the period size loses any relevance in terms of efficiency. Is there any gain if DMA chunks and period sizes are related in any way ? > > I could just leave the period size as a power of 2, on that way, a > > period would never cross any page boundary, but most ALSA programs are > > too picky to accept that kind of restrictions in most cases. > > Devices like usb and ymfpci have a fixed period size, but their > drivers emulate arbitrary period sizes. That means that those hwparam restrictions "should not be used" ?? After realizing that 99% of ALSA apps don't work when using them, renders them quiet useless. By the way, is it really really necesary that "snd_pcm_period_elapsed()" is called exactly when one period has been playback ? Must that callback be called for every period ? After looking at the bt87x driver it seems that it doesn't matter after all (is that right ?). I was thinking in calling snd_pcm_period_elapsed() just after each page crossing, instead of period crossing, for simplicity. Any comments ? Best Regards Manuel ------------------------------------------------------- SF.Net is sponsored by: Speed Start Your Linux Apps Now. Build and deploy apps & Web services for Linux with a free DVD software kit from IBM. Click Now! http://ads.osdn.com/?ad_id=1356&alloc_id=3438&op=click _______________________________________________ Alsa-devel mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/alsa-devel
