On Wed, Jun 20, 2018 at 11:19 AM Jassi Brar <jassisinghbrar@xxxxxxxxx> wrote: > > On Wed, Jun 20, 2018 at 8:32 PM, jonsmirl@xxxxxxxxx <jonsmirl@xxxxxxxxx> wrote: > > > > > > > > On Wed, Jun 20, 2018 at 9:36 AM Jassi Brar <jassisinghbrar@xxxxxxxxx> wrote: > >> > >> On Tue, Feb 13, 2018 at 3:02 PM, Robert Bielik <Robert.Bielik@xxxxxxxxx> wrote: > >> >> Enabling SOF interrupts will be a big pain :-) Well, enabling the > >> >> interrupt itself is a no-brainer, but it'll cause terrible CPU overload. > >> > > >> > Oh, I see. Hmm... would it be possible to allow upper levels to config this dynamically ? I.e. for the ALSA subsystem there is no need for the SOF timestamps, whereas for my proposal they would be needed. > >> > > >> > And what kind of CPU overhead are we talking about ? The IRQs shouldn't come more often than every 125 us, and all that is needed is to take a timestamp value But I'm probably overlooking a lot of stuff... > >> > > >> I believe we could control data rate precisely enough for the > >> feeedback ep to be needed only for compatibility with Windows (Linux > >> is already tested to work fine, MacOS is reported to have worked when > >> the code was upstreamed.). > > > > > > Right now Windows 10 (all I have checked) refuses to even connect to a Linux based UAC2 device. It appears to be complaining that no endpoint supporting USB_ENDPOINT_USAGE_FEEDBACK mode is implement. My five minutes of poking in the spec implies that implementing this is required for an endpoint doing USB_ENDPOINT_SYNC_ASYNC. Maybe this is something that can be faked to the point of allowing Windows to connect to the UAC2 gadget driver? > > > Thats what I meant. > > > The Windows error you get is: > > "The driver could not find a feedback endpoint for an asynchronous data OUT endpoint on device \Device\....." > > > For OUT, there might be some hoops to jump. Honestly it's been years > since I read the spec and got the code to work. I find it tempting to > look into Windows 10 as well, but I can't commit to a timeline. For my application there is no recording HW on the gadget. Maybe a quick way to fix this would be to make a flag to say that the gadget is output only? And then change the descriptors around? That would also help with my specific hardware case where the USB controller only supports ISOCHRONOUS in a single direction. Limitation of an Allwinner chip. > > Cheers! -- Jon Smirl jonsmirl@xxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
