Clemens:
> No USB device supports DMA transfers. USB devices support USB transfers.
> The host controller supports DMA transfers. Yours does, too.
Well, I thought so. But I even modified snd-usb-audio driver (quirks + other code) to support this card and what I get out of it is the same thing I got when I tried with DMA on my own: a kind of buzz sound that sometimes continues after stopping the playback.
As you can see from the code I posted I'm not going this way, I'm copying the data from runtime->dma_area into the URB transfer_buffer I allocate.
> You should copy the data just before you submit the URB. In other words,
> yes.
I copy and send in the same function, is it right?
> How do you determine how much data to send in each USB frame?
I use fixed sizes (as the windows' driver do). In snd_toneport.h each size is specified according to the different altsettings. Each URB has 2 isoch. packets of the same size.
Stefano
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