Chris McClimans <[email protected]> writes:
> It looks like the ordering may be important.
> Configuring uac2 as your first function seems to resolve the issue.
> Must be a requirement documented somewhere, or an interesting bug. :)
It's a bug in uac2. It statically sets the IAD bFirstInterface to 0
regardless of actual interface numbers being allocated to the function:
static struct usb_interface_assoc_descriptor iad_desc = {
.bLength = sizeof iad_desc,
.bDescriptorType = USB_DT_INTERFACE_ASSOCIATION,
.bFirstInterface = 0,
.bInterfaceCount = 3,
.bFunctionClass = USB_CLASS_AUDIO,
.bFunctionSubClass = UAC2_FUNCTION_SUBCLASS_UNDEFINED,
.bFunctionProtocol = UAC_VERSION_2,
};
Compare this to other functions with an IAD. They assign the IAD
bFirstInterface based on actual interface numbers allocated to the
function. Example from f_ecm.c:
static struct usb_interface_assoc_descriptor
ecm_iad_descriptor = {
.bLength = sizeof ecm_iad_descriptor,
.bDescriptorType = USB_DT_INTERFACE_ASSOCIATION,
/* .bFirstInterface = DYNAMIC, */
.bInterfaceCount = 2, /* control + data */
.bFunctionClass = USB_CLASS_COMM,
.bFunctionSubClass = USB_CDC_SUBCLASS_ETHERNET,
.bFunctionProtocol = USB_CDC_PROTO_NONE,
/* .iFunction = DYNAMIC */
};
..
static int
ecm_bind(struct usb_configuration *c, struct usb_function *f)
{
..
/* allocate instance-specific interface IDs */
status = usb_interface_id(c, f);
if (status < 0)
goto fail;
ecm->ctrl_id = status;
ecm_iad_descriptor.bFirstInterface = status;
ecm_control_intf.bInterfaceNumber = status;
ecm_union_desc.bMasterInterface0 = status;
Bjørn
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