HID: google: Enable PM Full On mode when adjusting backlight

hammer LED backlight brightness is not getting set when USB
device is in suspend state.

This patch fixes the issue by requesting USB HID device to be
in FULLON mode, so that sending hardware output report and
hardware raw request won't fail to set brightness, and set
device back to NORMAL mode once this call returns.
Signed-off-by: Haridhar Kalvala <haridhar.kalvala@intel.com>
Reviewed-by: Dmitry Torokhov <dtor@chromium.org>
Signed-off-by: Nicolas Boichat <drinkcat@chromium.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/hid-google-hammer.c

@@ -41,6 +41,16 @@ static int hammer_kbd_brightness_set_blocking(struct led_classdev *cdev,
 	led->buf[0] = 0;
 	led->buf[1] = br;
 
+	/*
+	 * Request USB HID device to be in Full On mode, so that sending
+	 * hardware output report and hardware raw request won't fail.
+	 */
+	ret = hid_hw_power(led->hdev, PM_HINT_FULLON);
+	if (ret < 0) {
+		hid_err(led->hdev, "failed: device not resumed %d\n", ret);
+		return ret;
+	}
+
 	ret = hid_hw_output_report(led->hdev, led->buf, sizeof(led->buf));
 	if (ret == -ENOSYS)
 		ret = hid_hw_raw_request(led->hdev, 0, led->buf,
@@ -50,6 +60,10 @@ static int hammer_kbd_brightness_set_blocking(struct led_classdev *cdev,
 	if (ret < 0)
 		hid_err(led->hdev, "failed to set keyboard backlight: %d\n",
 			ret);
+
+	/* Request USB HID device back to Normal Mode. */
+	hid_hw_power(led->hdev, PM_HINT_NORMAL);
+
 	return ret;
 }