ib-tb: support magic keyboard backlight

MacBookPro16,1/2/3/4 have the magic keyboard, with the keyboard
backlight controlled via the Touch Bar Backlight USB device.

We check that the internal keyboard's USB product ID matches that of
models with the magic keyboard, and then we create a sysfs led class
dev.

Author: Redecorating

apple-ib-tb.c

@@ -76,6 +76,8 @@
 
 #define APPLETB_MAX_DIM_TIME	30
 
+#define APPLE_MAGIC_KBD_BL_MAX	60
+
 static int appletb_tb_def_idle_timeout = 5 * 60;
 module_param_named(idle_timeout, appletb_tb_def_idle_timeout, int, 0444);
 MODULE_PARM_DESC(idle_timeout, "Default touch bar idle timeout:\n"
@@ -199,6 +201,24 @@ static const struct appletb_key_translation appletb_fn_codes[] = {
 	{ KEY_F12, KEY_VOLUMEUP },
 };
 
+struct apple_magic_backlight {
+	struct led_classdev cdev;
+	struct usb_device dev;
+};
+
+struct apple_magic_keyboard_backlight_report {
+	u8 report_id;	/* 0x01 */
+	u8 mode;	/* If 0x00, brightness can turn off backlight */
+	u8 brightness;
+	u8 override_1;	/* If these are non-zero, backlight is overridden to max brightness */
+	u8 override_2;
+	u8 max;		/* The lower this is, the brighter each brightness value is.
+			 * Only takes affect after turning it off and on again. */
+	u8 rate;
+	u8 magic_1;	/* If these are non-zero, we are ignored. */
+	u8 magic_2;
+};
+
 static struct appletb_device *appletb_dev;
 
 static int appletb_send_usb_ctrl(struct appletb_iface_info *iface_info,
@@ -319,6 +339,77 @@ static int appletb_send_hid_report(struct appletb_iface_info *iface_info,
 	return rc;
 }
 
+static int apple_magic_keyboard_backlight_set(struct apple_magic_backlight *backlight, char brightness, char rate)
+{
+	int tries = 0;
+	int rc;
+	struct apple_magic_keyboard_backlight_report *rep;
+
+	rep = kmalloc(sizeof(*rep), GFP_KERNEL);
+	if (rep == NULL)
+		return -ENOMEM;
+
+	rep->report_id = 0x01;
+	rep->mode = brightness;
+	rep->brightness = brightness;
+	rep->max = 0x5e;
+	rep->rate = rate;
+
+	do {
+		/*
+		 * FIXME: use appletb_send_hid_report, don't hard code all of this
+		 * Need to get apple_tb_send_hid_report to use wIndex=0x01
+		 */
+		rc = usb_control_msg(&backlight->dev,
+			usb_sndctrlpipe(&backlight->dev, 0),
+			HID_REQ_SET_REPORT, USB_DIR_OUT |
+			USB_TYPE_CLASS | USB_RECIP_INTERFACE,
+			0x0301, 0x01, rep, sizeof(*rep),
+			2000);
+		if (rc != -EPIPE)
+			break;
+
+		usleep_range(1000 << tries, 3000 << tries);
+	} while (++tries < 5);
+
+	kfree(rep);
+	return (rc > 0) ? 0 : rc;
+}
+
+static int apple_magic_keyboard_backlight_led_set(struct led_classdev *led_cdev,
+		enum led_brightness brightness)
+{
+	struct apple_magic_backlight *backlight = container_of(led_cdev,
+			struct apple_magic_backlight, cdev);
+
+	return apple_magic_keyboard_backlight_set(backlight, brightness, 1);
+}
+
+static int apple_magic_keyboard_backlight_init(struct appletb_device *tb_dev)
+{
+	int ret;
+	struct apple_magic_backlight *backlight;
+
+	backlight = devm_kzalloc(tb_dev->log_dev, sizeof(*backlight), GFP_KERNEL);
+	if (!backlight)
+		return -ENOMEM;
+
+	backlight->dev = *interface_to_usbdev(tb_dev->disp_iface.usb_iface);
+	backlight->cdev.name = "apple::kbd_backlight";
+	backlight->cdev.max_brightness = APPLE_MAGIC_KBD_BL_MAX;
+	backlight->cdev.brightness_set_blocking = apple_magic_keyboard_backlight_led_set;
+
+	ret = apple_magic_keyboard_backlight_set(backlight, 0, 0);
+	if (ret) {
+		dev_err(tb_dev->log_dev, "Failed to initialise Magic Keyboard Backlight (%d)\n", ret);
+		kfree(backlight);
+		return ret;
+	}
+
+	ret = devm_led_classdev_register(tb_dev->log_dev, &backlight->cdev);
+	return ret;
+}
+
 static int appletb_set_tb_disp(struct appletb_device *tb_dev,
 			       unsigned char disp)
 {
@@ -884,6 +975,13 @@ static int appletb_inp_connect(struct input_handler *handler,
 	if (id->driver_info == APPLETB_DEVID_KEYBOARD) {
 		handle = &tb_dev->kbd_handle;
 		handle->name = "tbkbd";
+		switch(dev->id.product) {
+			case 0x0340u: /* MacBookPro16,1/4 */
+			case 0x027eu: /* MacBookPro16,2 */
+			case 0x027fu: /* MacBookPro16,3 */
+				apple_magic_keyboard_backlight_init(tb_dev);
+				break;
+		}
 	} else if (id->driver_info == APPLETB_DEVID_TOUCHPAD) {
 		handle = &tb_dev->tpd_handle;
 		handle->name = "tbtpad";