Hi,
Robert Bielik <Robert.Bielik@xxxxxxxxx> writes:
>> > It seems such a feedback endpoint is now required by the standard:
>> > "The USB 2.0 specification states that if isochronous OUT data
>> > endpoint uses the asynchronous synchronization, an isochronous
>> > feedback endpoint is needed."
>>
>> We actually have both EP IN and EP OUT on the UAC2 function:
>>
>> 272:static struct usb_endpoint_descriptor fs_epout_desc = {
>> 282:static struct usb_endpoint_descriptor hs_epout_desc = {
>> 349:static struct usb_endpoint_descriptor fs_epin_desc = {
>> 359:static struct usb_endpoint_descriptor hs_epin_desc = {
>
> Yes, but that isn't the issue AFAIU ? In the USB 2.0 standard related
> to synchronization
> (http://sdphca.ucsd.edu/lab_equip_manuals/usb_20.pdf chapter 5.12.4),
> an isochronous OUT ep with asynchronous synchronization is *required*
> (at least by Microsoft) to have a feedback IN ep, to be able to report
> to the host the rate so no under- or overrun condition occurs.
Indeed, that's also mandated by USB spec. Seems like we need to patch
f_uac2.c. Can you check if setting the IN endpoint as implicit feedback
data is enough?
modified drivers/usb/gadget/function/f_uac2.c
@@ -351,7 +351,8 @@ static struct usb_endpoint_descriptor fs_epin_desc = {
.bDescriptorType = USB_DT_ENDPOINT,
.bEndpointAddress = USB_DIR_IN,
- .bmAttributes = USB_ENDPOINT_XFER_ISOC | USB_ENDPOINT_SYNC_ASYNC,
+ .bmAttributes = USB_ENDPOINT_XFER_ISOC | USB_ENDPOINT_SYNC_ASYNC |
+ USB_ENDPOINT_USAGE_IMPLICIT_FB,
.wMaxPacketSize = cpu_to_le16(1023),
.bInterval = 1,
};
@@ -360,7 +361,8 @@ static struct usb_endpoint_descriptor hs_epin_desc = {
.bLength = USB_DT_ENDPOINT_SIZE,
.bDescriptorType = USB_DT_ENDPOINT,
- .bmAttributes = USB_ENDPOINT_XFER_ISOC | USB_ENDPOINT_SYNC_ASYNC,
+ .bmAttributes = USB_ENDPOINT_XFER_ISOC | USB_ENDPOINT_SYNC_ASYNC |
+ USB_ENDPOINT_USAGE_IMPLICIT_FB,
.wMaxPacketSize = cpu_to_le16(1024),
.bInterval = 4,
};
--
balbi
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