samples: usb: hid-keyboard: enable and use remote wakeup on button press

USB remote wakeup capability is a common feature of keyboards,
allowing them to wake up a suspended host. Currently there is no USB sample
that demonstrates remote wakeup, which makes basic evaluation of the
functionality non-trivial.

Modify the hid-keyboard sample with a minimalistic solution
of demonstrating remote wakeup capability. While it is not required to have
been configured prior to suspend to issue a wakeup request, from usability
perspective I'd say it makes sense.

Signed-off-by: Benedek Kupper <kupper.benedek@gmail.com>

Author: benedekkupper

samples/subsys/usb/hid-keyboard/prj.conf

@@ -6,6 +6,7 @@ CONFIG_USBD_LOG_LEVEL_WRN=y
 CONFIG_USBD_HID_LOG_LEVEL_WRN=y
 CONFIG_UDC_DRIVER_LOG_LEVEL_WRN=y
 CONFIG_SAMPLE_USBD_PID=0x0007
+CONFIG_SAMPLE_USBD_REMOTE_WAKEUP=y
 
 CONFIG_GPIO=y
 CONFIG_INPUT=y

samples/subsys/usb/hid-keyboard/src/main.c

@@ -279,6 +279,17 @@ int main(void)
 			continue;
 		}
 
+		if (usbd_is_suspended(sample_usbd)) {
+			/* on a press of any button, send wakeup request */
+			if (kb_evt.value) {
+				ret = usbd_wakeup_request(sample_usbd);
+				if (ret) {
+					LOG_ERR("Remote wakeup error, %d", ret);
+				}
+			}
+			continue;
+		}
+
 		ret = hid_device_submit_report(hid_dev, KB_REPORT_COUNT, report);
 		if (ret) {
 			LOG_ERR("HID submit report error, %d", ret);