Re: usb:gadget:f_uac2: EP OUT is adaptive instead of async

[Pavel Hofman <pavel.hofman@ivitera.com>]

Dne 06. 02. 20 v 16:41 Greg KH napsal(a):
> On Thu, Feb 06, 2020 at 02:22:47PM +0100, Pavel Hofman wrote:
>> Hi,
>>
>> The existing UAC2 implementation presents itself as asynchronous
>> USB_ENDPOINT_SYNC_ASYNC https://github.com/torvalds/linux/blob/master/drivers/usb/gadget/function/f_uac2.c#L276
>> + https://github.com/torvalds/linux/blob/master/drivers/usb/gadget/function/f_uac2.c#L285
>> .
>>
>> However:
>> 1) The function does not define any feedback endpoint
>>
>> 2) IMO in reality it is adaptive - the g_audio capture device accepts any
>> data passed by the USB host, the USB host is the one which defines the data
>> pace.
>>
>> While Linux and reportedly OSX accept the async EP OUT without explicit
>> feedback EP IN, Windows does not.
>>
>> Simply changing USB_ENDPOINT_SYNC_ASYNC to USB_ENDPOINT_SYNC_ADAPTIVE for
>> the FS and HS output endpoints fixes the windows problem and IMO corrects
>> the config to reflect real function.
>>
>> There are multiple projects underway adding the async feedback EP, but in
>> the meantime I think the .bmAttributes information should be changed as
>> above, making the device usable in Windows for everyone.
>>
>> Thanks a lot for considering.
> 
> Patches work best, can you create them and test and then submit?
> 

No problem, I have tested for a few months. I just did not know if you 
would accept such change. I will send the patch then :-)

Thanks,

Pavel.