[PATCH v4] HID: magicmouse: add battery reporting for Magic Trackpad v1

[Damiano Gragnaniello <damianogragnaniello@gmail.com>]

The Magic Trackpad v1 (A1339) reports battery level via Bluetooth using
Report ID 0x47. This patch adds support for parsing this report and
registering a power_supply interface so that userspace (upower) can
correctly display the battery percentage for this legacy device.

Signed-off-by: Damiano Gragnaniello <damianogragnaniello@gmail.com>
---
v4:
  - Fixed patch formatting and spacing issues to ensure clean application.
  - Removed local path references and non-technical notes.
  - Corrected diff headers.
v3:
  - Fixed changelog language (translated from Italian to English).
  - Standardized patch naming for upstream submission.
v2:
  - Rename macros to TRACKPAD_V1_BATTERY_REPORT_ID for clarity.
  - Add clamp_val() to ensure battery capacity stays within 0-100 range.
  - Restore original driver comments.

 drivers/hid/hid-magicmouse.c | 56 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 56 insertions(+)

diff --git a/drivers/hid/hid-magicmouse.c b/drivers/hid/hid-magicmouse.c
index 79a60c6..82b3c1d 100644
--- a/drivers/hid/hid-magicmouse.c
+++ b/drivers/hid/hid-magicmouse.c
@@ -62,6 +62,8 @@
 #define TRACKPAD_REPORT_ID 0x28
 #define TRACKPAD2_USB_REPORT_ID 0x02
 #define TRACKPAD2_BT_REPORT_ID 0x31
+#define TRACKPAD_V1_BATTERY_REPORT_ID 0x47
+#define TRACKPAD_V1_BATTERY_TIMEOUT_SEC 60
 #define MOUSE_REPORT_ID    0x29
 #define MOUSE2_REPORT_ID   0x12
 #define DOUBLE_REPORT_ID   0xf7
@@ -156,6 +158,44 @@ struct magicmouse_sc {
 	struct hid_device *hdev;
 	struct delayed_work work;
 	struct timer_list battery_timer;
+
+	/* Magic Trackpad v1 battery support */
+	struct power_supply *battery;
+	struct power_supply_desc battery_desc;
+	char battery_name[64];
+	int battery_capacity;
+};
+
+static const enum power_supply_property magicmouse_v1_battery_props[] = {
+	POWER_SUPPLY_PROP_PRESENT,
+	POWER_SUPPLY_PROP_CAPACITY,
+	POWER_SUPPLY_PROP_SCOPE,
+	POWER_SUPPLY_PROP_STATUS,
+};
+
+static int magicmouse_v1_battery_get_property(struct power_supply *psy,
+					   enum power_supply_property psp,
+					   union power_supply_propval *val)
+{
+	struct magicmouse_sc *msc = power_supply_get_drvdata(psy);
+
+	switch (psp) {
+	case POWER_SUPPLY_PROP_PRESENT:
+		val->intval = 1;
+		break;
+	case POWER_SUPPLY_PROP_CAPACITY:
+		val->intval = msc->battery_capacity;
+		break;
+	case POWER_SUPPLY_PROP_SCOPE:
+		val->intval = POWER_SUPPLY_SCOPE_DEVICE;
+		break;
+	case POWER_SUPPLY_PROP_STATUS:
+		val->intval = POWER_SUPPLY_STATUS_DISCHARGING;
+		break;
+	default:
+		return -EINVAL;
+	}
+	return 0;
 }
 
 static int magicmouse_firm_touch(struct magicmouse_sc *msc)
@@ -434,6 +474,16 @@ static int magicmouse_raw_event(struct hid_device *hdev,
 
 	switch (data[0]) {
+	case TRACKPAD_V1_BATTERY_REPORT_ID:
+		if (size < 2)
+			return 0;
+		if (msc->battery) {
+			msc->battery_capacity = clamp_val((int)data[1], 0, 100);
+			power_supply_changed(msc->battery);
+		}
+		return 0;
 	case TRACKPAD_REPORT_ID:
 	case TRACKPAD2_BT_REPORT_ID:
 		/* Expect four bytes of prefix, and N*9 bytes of touch data. */
@@ -939,6 +989,32 @@ static int magicmouse_probe(struct hid_device *hdev,
 		magicmouse_fetch_battery(hdev);
 	}
 
+	if (id->product == USB_DEVICE_ID_APPLE_MAGICTRACKPAD &&
+	    id->vendor == USB_VENDOR_ID_APPLE) {
+		struct power_supply_config psy_cfg = {};
+
+		psy_cfg.drv_data = msc;
+		msc->battery_capacity = 0;
+		snprintf(msc->battery_name, sizeof(msc->battery_name),
+			 "hid-magictrackpad-v1-%s", dev_name(&hdev->dev));
+
+		msc->battery_desc.name           = msc->battery_name;
+		msc->battery_desc.type           = POWER_SUPPLY_TYPE_BATTERY;
+		msc->battery_desc.properties     = magicmouse_v1_battery_props;
+		msc->battery_desc.num_properties = ARRAY_SIZE(magicmouse_v1_battery_props);
+		msc->battery_desc.get_property   = magicmouse_v1_battery_get_property;
+
+		msc->battery = devm_power_supply_register(&hdev->dev,
+							  &msc->battery_desc,
+							  &psy_cfg);
+		if (IS_ERR(msc->battery)) {
+			hid_err(hdev, "can't register battery device\n");
+			msc->battery = NULL;
+		}
+	}
+
 	return 0;
 }