HID: playstation: use DualSense MAC address as unique identifier.

Use the DualSense MAC address as a unique identifier for the HID device.
Signed-off-by: Roderick Colenbrander <roderick.colenbrander@sony.com>
Reviewed-by: Barnabás Pőcze <pobrn@protonmail.com>
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>

drivers/hid/hid-playstation.c

@@ -20,6 +20,7 @@
 /* Base class for playstation devices. */
 struct ps_device {
 	struct hid_device *hdev;
+	uint8_t mac_address[6]; /* Note: stored in little endian order. */
 
 	int (*parse_report)(struct ps_device *dev, struct hid_report *report, u8 *data, int size);
 };
@@ -27,6 +28,9 @@ struct ps_device {
 #define DS_INPUT_REPORT_USB			0x01
 #define DS_INPUT_REPORT_USB_SIZE		64
 
+#define DS_FEATURE_REPORT_PAIRING_INFO		0x09
+#define DS_FEATURE_REPORT_PAIRING_INFO_SIZE	20
+
 /* Button masks for DualSense input report. */
 #define DS_BUTTONS0_HAT_SWITCH	GENMASK(3, 0)
 #define DS_BUTTONS0_SQUARE	BIT(4)
@@ -166,6 +170,53 @@ static struct input_dev *ps_gamepad_create(struct hid_device *hdev)
 	return gamepad;
 }
 
+static int ps_get_report(struct hid_device *hdev, uint8_t report_id, uint8_t *buf, size_t size)
+{
+	int ret;
+
+	ret = hid_hw_raw_request(hdev, report_id, buf, size, HID_FEATURE_REPORT,
+				 HID_REQ_GET_REPORT);
+	if (ret < 0) {
+		hid_err(hdev, "Failed to retrieve feature with reportID %d: %d\n", report_id, ret);
+		return ret;
+	}
+
+	if (ret != size) {
+		hid_err(hdev, "Invalid byte count transferred, expected %zu got %d\n", size, ret);
+		return -EINVAL;
+	}
+
+	if (buf[0] != report_id) {
+		hid_err(hdev, "Invalid reportID received, expected %d got %d\n", report_id, buf[0]);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int dualsense_get_mac_address(struct dualsense *ds)
+{
+	uint8_t *buf;
+	int ret = 0;
+
+	buf = kzalloc(DS_FEATURE_REPORT_PAIRING_INFO_SIZE, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	ret = ps_get_report(ds->base.hdev, DS_FEATURE_REPORT_PAIRING_INFO, buf,
+			DS_FEATURE_REPORT_PAIRING_INFO_SIZE);
+	if (ret) {
+		hid_err(ds->base.hdev, "Failed to retrieve DualSense pairing info: %d\n", ret);
+		goto err_free;
+	}
+
+	memcpy(ds->base.mac_address, &buf[1], sizeof(ds->base.mac_address));
+
+err_free:
+	kfree(buf);
+	return ret;
+}
+
 static int dualsense_parse_report(struct ps_device *ps_dev, struct hid_report *report,
 		u8 *data, int size)
 {
@@ -237,6 +288,13 @@ static struct ps_device *dualsense_create(struct hid_device *hdev)
 	ds->base.parse_report = dualsense_parse_report;
 	hid_set_drvdata(hdev, ds);
 
+	ret = dualsense_get_mac_address(ds);
+	if (ret) {
+		hid_err(hdev, "Failed to get MAC address from DualSense\n");
+		return ERR_PTR(ret);
+	}
+	snprintf(hdev->uniq, sizeof(hdev->uniq), "%pMR", ds->base.mac_address);
+
 	ds->gamepad = ps_gamepad_create(hdev);
 	if (IS_ERR(ds->gamepad)) {
 		ret = PTR_ERR(ds->gamepad);