В Сб, 25/04/2020 в 20:06 +0200, Pavel Hofman пишет:

Dne 25. 04. 20 v 14:06 Alexander Tsoy napsal(a):

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В Пт, 24/04/2020 в 11:42 +0200, Pavel Hofman пишет:

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Hi,

Please does the current USB audio driver support multiple transactions per microframe (high-bandwidth mode)? I could not find it in endpoint.c but it may be there or somewhere else :-)

This should be transparent for the driver. See usb_submit_urb() function from drivers/usb/core/urb.c. It allows packets larger than 1024 for isochronous transfers over High Speed and Super Speed buses.

Alexander, thanks a lot for the info and hint, indeed at https://github.com/torvalds/linux/blob/master/drivers/usb/core/urb.c#L444

And I just noticed that USB-audio driver can't properly parse max packet size for SuperSpeed and SuperSpeed+ devices yet. See audio_format_alloc_init().

On Sun, 26 Apr 2020 10:55:32 +0200, Pavel Hofman wrote:

Dne 25. 04. 20 v 21:50 Alexander Tsoy napsal(a):

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В Сб, 25/04/2020 в 20:06 +0200, Pavel Hofman пишет:

And I just noticed that USB-audio driver can't properly parse max packet size for SuperSpeed and SuperSpeed+ devices yet. See audio_format_alloc_init().

Very good catch. IIUC there are two basically equivalent calculations for HighSpeed -

https://elixir.bootlin.com/linux/v5.6.7/source/drivers/usb/core/urb.c#L445

https://elixir.bootlin.com/linux/v5.6.7/source/sound/usb/stream.c#L691

And audio_format_alloc_init missing the sections for SS, SS+ in usb_submit_urb . Perhpas a common method to make the calculation for all cases would make it more robust?

Yes, a common USB helper function sounds like a good idea.

thanks,

Takashi