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

[Ruslan Bilovol <ruslan.bilovol@gmail.com>]

On Thu, Feb 6, 2020 at 3:35 PM Pavel Hofman <pavel.hofman@ivitera.com> 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.

Are you working on async feedback EP implementation? I'm interested in that
feature and I can implement it soon but do not want to do double work
if somebody
is already working on it and will send to the community soon

Thanks,
Ruslan

>
> Thanks a lot for considering.
>
> Best regards,
>
> Pavel.