usb: gadget: uvc: Disable interrupt endpoint by default

The f_uvc code includes an interrupt endpoint against the VideoControl
interface. According to section 2.4.2 of the UVC specification however
this endpoint is optional in at least some cases:

"This endpoint is optional, but may be mandatory under certain
conditions"

The conditions enumerated are whether...

1. The device supports hardware triggers
2. The device implements any AutoUpdate controls
3. The device implements any Asynchronous controls

As all of those things are implementation dependent, this endpoint
might be unnecessary for some users. Further to that it is unusable
in the current implementation as there is no mechanism within the
UVC gadget driver that allows data to be sent over that endpoint.
Disable the interrupt endpoint by default, but check whether the
user has asked for it to be enabled in configfs and continue to
generate it if so.

Signed-off-by: Daniel Scally <dan.scally@ideasonboard.com>
Link: https://lore.kernel.org/r/20230130105045.120886-4-dan.scally@ideasonboard.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 1 insertions, 0 deletions

diff --git a/drivers/usb/gadget/function/uvc.h b/drivers/usb/gadget/function/uvc.h
index 48b71e04c2b1..daf226610f49 100644
--- a/drivers/usb/gadget/function/uvc.h
+++ b/drivers/usb/gadget/function/uvc.h
@@ -149,6 +149,7 @@ struct uvc_device {
 	struct usb_ep *interrupt_ep;
 	struct usb_request *control_req;
 	void *control_buf;
+	bool enable_interrupt_ep;
 
 	unsigned int streaming_intf;