Adding USB device quirk - packet format?

[Takashi Iwai]

On Thu, 16 Jul 2020 23:15:16 +0200,
Olivia Mackintosh wrote:
> 
> Hello,
> 
> I am trying to add a device quirk for the Pioneer DJM-750 mixer. I have
> attached a patch to illustrate what I'm trying to achieve. It is nearly
> identical to https://patchwork.kernel.org/patch/11521019/ except for the
> differences in channels. I have verified the settings against valid USB
> transfers.
> 
> While observing behaviour with a Windows 10 VM, the 8 pieces of data
> appear to be 8 isochronous packets within a single frame as opposed to 8
> microframes (each with their own transfer). Should this have any impact
> on the ability for the device to function? If so, is there a setting I
> am missing to account for this? Or, am I simply clutching at straws and
> completely on the wrong path.

It's rather a generic USB-audio issue, not specific to your device,
about how to set up URBs.  This influences on the performance, yes; it
defines stability vs latency.  On Linux driver, the condition varies
depending on the hw_params.

> This is rather device specific so I would not expect anyone to help
> troubleshoot this specific device but what I suspect is the problem is
> the way the audio data is arranged in the transfer.
> 
> Any suggestions and pointers on how to proceed are very much
> appreciated.

So did you see any actual problem with your patch?


thanks,

Takashi