Dne 11. 02. 20 v 17:16 Ruslan Bilovol napsal(a):
> On Fri, Feb 7, 2020 at 6:55 PM Pavel Hofman <pavel.hofman@xxxxxxxxxxx> wrote:
>>
>> The existing UAC2 implementation presents its EP OUT as
>> USB_ENDPOINT_SYNC_ASYNC.
>>
>> However:
>> 1) f_uac2 does not define any feedback endpoint
>>
>> 2) IMO in reality it is adaptive - the USB host is the one which sets
>> the pace of data.
>>
>> Changing USB_ENDPOINT_SYNC_ASYNC to USB_ENDPOINT_SYNC_ADAPTIVE for the FS
>> and HS output endpoints corrects the config to reflect real functionality.
>
> That's a good idea but ADAPTIVE endpoint still requires feedback endpoint for
> source (USB IN) case so the host can synchronize with such endpoint
> (see 3.16.2.2 of
> UAC2 spec "For adaptive audio source endpoints and asynchronous audio sink
> endpoints, an explicit synchronization mechanism is needed to maintain
> synchronization
> during transfers").
I apologize for missing this message. Please can we resume the discussion?
The tested combination is (not-changed) async IN and (changed) adaptive
OUT, which is what most USB-adaptive soundcards use. Such combination
does not require any feedback endpoint.
>
>>
>> Also, the change makes the UAC2 gadget recognized and working
>> in MS Windows.
>
> Does it recognizes well with both IN and OUT (e.g. capture+playback enabled)
> adaptive endpoints?
Only OUT is adaptive, IN stays async.
Thanks a lot,
Pavel.
>
> Thanks,
> Ruslan
>
>>
>> Signed-off-by: Pavel Hofman <pavel.hofman@xxxxxxxxxxx>
>> ---
>> drivers/usb/gadget/function/f_uac2.c | 4 ++--
>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/usb/gadget/function/f_uac2.c
>> b/drivers/usb/gadget/function/f_uac2.c
>> index db2d498..e8c9dd1 100644
>> --- a/drivers/usb/gadget/function/f_uac2.c
>> +++ b/drivers/usb/gadget/function/f_uac2.c
>> @@ -273,7 +273,7 @@ enum {
>> .bDescriptorType = USB_DT_ENDPOINT,
>>
>> .bEndpointAddress = USB_DIR_OUT,
>> - .bmAttributes = USB_ENDPOINT_XFER_ISOC | USB_ENDPOINT_SYNC_ASYNC,
>> + .bmAttributes = USB_ENDPOINT_XFER_ISOC | USB_ENDPOINT_SYNC_ADAPTIVE,
>> .wMaxPacketSize = cpu_to_le16(1023),
>> .bInterval = 1,
>> };
>> @@ -282,7 +282,7 @@ enum {
>> .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_ADAPTIVE,
>> .wMaxPacketSize = cpu_to_le16(1024),
>> .bInterval = 4,
>> };
>> --
>> 1.9.1
>
