[PATCH 3/3] HID: apple: Report Magic Keyboard battery over USB

[José Expósito]

When connected over USB, the Apple Magic Keyboard 2015 registers 3
different interfaces. One of them is used to report the battery level.

However, unlike when connected over Bluetooth, the battery level is not
reported automatically and it is required to fetch it manually.

Add a new quirk to fix the battery report descriptor and a timer to
fetch the battery level.

Signed-off-by: José Expósito <jose.exposito89@xxxxxxxxx>
---
 drivers/hid/hid-apple.c | 87 ++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 85 insertions(+), 2 deletions(-)

diff --git a/drivers/hid/hid-apple.c b/drivers/hid/hid-apple.c
index b34aeed292a2..2bd8276411e0 100644
--- a/drivers/hid/hid-apple.c
+++ b/drivers/hid/hid-apple.c
@@ -16,8 +16,10 @@
 
 #include <linux/device.h>
 #include <linux/hid.h>
+#include <linux/jiffies.h>
 #include <linux/module.h>
 #include <linux/slab.h>
+#include <linux/timer.h>
 
 #include "hid-ids.h"
 
@@ -30,10 +32,12 @@
 #define APPLE_INVERT_HWHEEL	BIT(6)
 /* BIT(7) reserved, was: APPLE_IGNORE_HIDINPUT */
 #define APPLE_NUMLOCK_EMULATION	BIT(8)
+#define APPLE_RDESC_BATTERY	BIT(9)
 
 #define APPLE_FLAG_FKEY		0x01
 
 #define HID_COUNTRY_INTERNATIONAL_ISO	13
+#define APPLE_BATTERY_TIMEOUT_MS	60000
 
 static unsigned int fnmode = 1;
 module_param(fnmode, uint, 0644);
@@ -58,10 +62,12 @@ MODULE_PARM_DESC(swap_fn_leftctrl, "Swap the Fn and left Control keys. "
 		"[0] = as-is, Mac layout, 1 = swapped, PC layout)");
 
 struct apple_sc {
+	struct hid_device *hdev;
 	unsigned long quirks;
 	unsigned int fn_on;
 	unsigned int fn_found;
 	DECLARE_BITMAP(pressed_numlock, KEY_CNT);
+	struct timer_list battery_timer;
 };
 
 struct apple_key_translation {
@@ -333,6 +339,43 @@ static int apple_event(struct hid_device *hdev, struct hid_field *field,
 	return 0;
 }
 
+static int apple_fetch_battery(struct hid_device *hdev)
+{
+#ifdef CONFIG_HID_BATTERY_STRENGTH
+	struct apple_sc *asc = hid_get_drvdata(hdev);
+	struct hid_report_enum *report_enum;
+	struct hid_report *report;
+
+	if (!(asc->quirks & APPLE_RDESC_BATTERY) || !hdev->battery)
+		return -1;
+
+	report_enum = &hdev->report_enum[hdev->battery_report_type];
+	report = report_enum->report_id_hash[hdev->battery_report_id];
+
+	if (!report || report->maxfield < 1)
+		return -1;
+
+	if (hdev->battery_capacity == hdev->battery_max)
+		return -1;
+
+	hid_hw_request(hdev, report, HID_REQ_GET_REPORT);
+	return 0;
+#else
+	return -1;
+#endif
+}
+
+static void apple_battery_timer_tick(struct timer_list *t)
+{
+	struct apple_sc *asc = from_timer(asc, t, battery_timer);
+	struct hid_device *hdev = asc->hdev;
+
+	if (apple_fetch_battery(hdev) == 0) {
+		mod_timer(&asc->battery_timer,
+			  jiffies + msecs_to_jiffies(APPLE_BATTERY_TIMEOUT_MS));
+	}
+}
+
 /*
  * MacBook JIS keyboard has wrong logical maximum
  * Magic Keyboard JIS has wrong logical maximum
@@ -354,6 +397,30 @@ static __u8 *apple_report_fixup(struct hid_device *hdev, __u8 *rdesc,
 			 "fixing up MacBook JIS keyboard report descriptor\n");
 		rdesc[53] = rdesc[59] = 0xe7;
 	}
+
+	/*
+	 * Change the usage from:
+	 *   0x06, 0x00, 0xff, // Usage Page (Vendor Defined Page 1)  0
+	 *   0x09, 0x0b,       // Usage (Vendor Usage 0x0b)           3
+	 * To:
+	 *   0x05, 0x01,       // Usage Page (Generic Desktop)        0
+	 *   0x09, 0x06,       // Usage (Keyboard)                    2
+	 */
+	if ((asc->quirks & APPLE_RDESC_BATTERY) && *rsize == 83 &&
+	    rdesc[46] == 0x84 && rdesc[58] == 0x85) {
+		hid_info(hdev,
+			 "fixing up Magic Keyboard battery report descriptor\n");
+		*rsize = *rsize - 1;
+		rdesc = kmemdup(rdesc + 1, *rsize, GFP_KERNEL);
+		if (!rdesc)
+			return NULL;
+
+		rdesc[0] = 0x05;
+		rdesc[1] = 0x01;
+		rdesc[2] = 0x09;
+		rdesc[3] = 0x06;
+	}
+
 	return rdesc;
 }
 
@@ -447,6 +514,7 @@ static int apple_probe(struct hid_device *hdev,
 		return -ENOMEM;
 	}
 
+	asc->hdev = hdev;
 	asc->quirks = quirks;
 
 	hid_set_drvdata(hdev, asc);
@@ -463,9 +531,23 @@ static int apple_probe(struct hid_device *hdev,
 		return ret;
 	}
 
+	timer_setup(&asc->battery_timer, apple_battery_timer_tick, 0);
+	mod_timer(&asc->battery_timer,
+		  jiffies + msecs_to_jiffies(APPLE_BATTERY_TIMEOUT_MS));
+	apple_fetch_battery(hdev);
+
 	return 0;
 }
 
+static void apple_remove(struct hid_device *hdev)
+{
+	struct apple_sc *asc = hid_get_drvdata(hdev);
+
+	del_timer_sync(&asc->battery_timer);
+
+	hid_hw_stop(hdev);
+}
+
 static const struct hid_device_id apple_devices[] = {
 	{ HID_USB_DEVICE(USB_VENDOR_ID_APPLE, USB_DEVICE_ID_APPLE_MIGHTYMOUSE),
 		.driver_data = APPLE_MIGHTYMOUSE | APPLE_INVERT_HWHEEL },
@@ -540,11 +622,11 @@ static const struct hid_device_id apple_devices[] = {
 	{ HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_APPLE, USB_DEVICE_ID_APPLE_ALU_WIRELESS_JIS),
 		.driver_data = APPLE_NUMLOCK_EMULATION | APPLE_HAS_FN },
 	{ HID_USB_DEVICE(USB_VENDOR_ID_APPLE, USB_DEVICE_ID_APPLE_MAGIC_KEYBOARD_2015),
-		.driver_data = APPLE_HAS_FN | APPLE_ISO_TILDE_QUIRK },
+		.driver_data = APPLE_HAS_FN | APPLE_ISO_TILDE_QUIRK | APPLE_RDESC_BATTERY },
 	{ HID_BLUETOOTH_DEVICE(BT_VENDOR_ID_APPLE, USB_DEVICE_ID_APPLE_MAGIC_KEYBOARD_2015),
 		.driver_data = APPLE_HAS_FN | APPLE_ISO_TILDE_QUIRK },
 	{ HID_USB_DEVICE(USB_VENDOR_ID_APPLE, USB_DEVICE_ID_APPLE_MAGIC_KEYBOARD_NUMPAD_2015),
-		.driver_data = APPLE_HAS_FN | APPLE_ISO_TILDE_QUIRK },
+		.driver_data = APPLE_HAS_FN | APPLE_ISO_TILDE_QUIRK | APPLE_RDESC_BATTERY },
 	{ HID_BLUETOOTH_DEVICE(BT_VENDOR_ID_APPLE, USB_DEVICE_ID_APPLE_MAGIC_KEYBOARD_NUMPAD_2015),
 		.driver_data = APPLE_HAS_FN | APPLE_ISO_TILDE_QUIRK },
 	{ HID_USB_DEVICE(USB_VENDOR_ID_APPLE, USB_DEVICE_ID_APPLE_WELLSPRING_ANSI),
@@ -650,6 +732,7 @@ static struct hid_driver apple_driver = {
 	.id_table = apple_devices,
 	.report_fixup = apple_report_fixup,
 	.probe = apple_probe,
+	.remove = apple_remove,
 	.event = apple_event,
 	.input_mapping = apple_input_mapping,
 	.input_mapped = apple_input_mapped,
-- 
2.25.1