[PATCH v12 14/17] HID: asus: expose XG Mobile identity and firmware information

[Denis Benato <denis.benato@linux.dev>]

The identity query also reports the mainboard part number, the serial
number and the part number of the station, and the 0xCE 0x03 query
answers with an 8-byte binary blob followed by "tag, length, data"
fields where GEN holds the station generation and VER the firmware
version.

Collect this information at probe time and expose it read-only on the
HID device:

  /sys/bus/hid/devices/<bus>:<addr>.<intf>/xgm_model             (PRO)
  .../xgm_serial                                              (SN)
  .../xgm_mainboard                                           (MB)
  .../xgm_part_number                                         (PNUM)
  .../xgm_firmware_version                                    (VER)
  .../xgm_generation                                          (GEN)

Signed-off-by: Denis Benato <denis.benato@linux.dev>
---
 drivers/hid/hid-asus.c | 188 ++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 186 insertions(+), 2 deletions(-)

diff --git a/drivers/hid/hid-asus.c b/drivers/hid/hid-asus.c
index 215628393765..691303b1a13f 100644
--- a/drivers/hid/hid-asus.c
+++ b/drivers/hid/hid-asus.c
@@ -74,6 +74,7 @@ MODULE_DESCRIPTION("Asus HID Keyboard and TouchPad");
 /* XG Mobile station protocol on FEATURE_KBD_LED_REPORT_ID2. */
 #define ASUS_XGM_CMD_QUERY 0xce
 #define ASUS_XGM_QUERY_IDENTITY 0x01
+#define ASUS_XGM_QUERY_VERSION 0x03
 #define ASUS_XGM_INFO_LEN 32
 
 /* Identity string fields, each "TAG:value;" inside the query answer. */
@@ -81,6 +82,12 @@ MODULE_DESCRIPTION("Asus HID Keyboard and TouchPad");
 #define ASUS_XGM_TAG_SERIAL	"SN:"
 #define ASUS_XGM_TAG_MODEL	"PRO:"
 #define ASUS_XGM_TAG_PART	"PNUM:"
+#define ASUS_XGM_TAG_GENERATION	"GEN"
+#define ASUS_XGM_TAG_FIRMWARE	"VER"
+
+/* A version field is a 3-character tag, one length byte, then the data. */
+#define ASUS_XGM_TLV_TAG_LEN	3
+#define ASUS_XGM_TLV_HDR_LEN	(ASUS_XGM_TLV_TAG_LEN + 1)
 
 /*
  * Every station answer echoes the report id, the opcode and the
@@ -236,6 +243,8 @@ struct asus_xgm_info {
 	char serial[ASUS_XGM_INFO_LEN];
 	char model[ASUS_XGM_INFO_LEN];
 	char part_number[ASUS_XGM_INFO_LEN];
+	char firmware_version[ASUS_XGM_INFO_LEN];
+	char generation[ASUS_XGM_INFO_LEN];
 };
 
 struct asus_touchpad_info {
@@ -5070,6 +5079,153 @@ static bool asus_xgm_is_supported_model(const struct asus_xgm_info *info)
 	return false;
 }
 
+/**
+ * asus_xgm_tlv_str() - Extract a "tag, length, data" field
+ * @dst: destination buffer
+ * @dst_len: size of @dst, including the trailing NUL
+ * @buf: answer of a version query
+ * @len: size of @buf
+ * @tag: three-character tag to look for
+ *
+ * Return: 0 on success, -ENOENT if @tag is missing or its data does not
+ * fit in @dst.
+ */
+static int asus_xgm_tlv_str(char *dst, size_t dst_len, const u8 *buf,
+			    size_t len, const char *tag)
+{
+	const u8 *p = buf + ASUS_XGM_RESP_PAYLOAD;
+	const u8 *end = buf + len;
+	u8 n;
+
+	/*
+	 * The payload starts with a binary prefix and then the fields.
+	 * The station pads between fields with 0xff, so the tag is sought
+	 * at every byte rather than walked as a packed list.
+	 */
+	while (p + ASUS_XGM_TLV_HDR_LEN <= end) {
+		if (!memcmp(p, tag, ASUS_XGM_TLV_TAG_LEN)) {
+			n = p[ASUS_XGM_TLV_TAG_LEN];
+
+			if (n >= dst_len ||
+			    end - (p + ASUS_XGM_TLV_HDR_LEN) < n)
+				return -ENOENT;
+
+			memcpy(dst, p + ASUS_XGM_TLV_HDR_LEN, n);
+			dst[n] = '\0';
+			return 0;
+		}
+
+		p++;
+	}
+
+	return -ENOENT;
+}
+
+/**
+ * asus_xgm_get_version() - Query the firmware version of a station
+ * @hdev: HID device
+ * @info: identity structure whose generation and firmware_version fields
+ * get filled in
+ *
+ * Return: 0 on success, negative errno on failure.
+ */
+static int asus_xgm_get_version(struct hid_device *hdev,
+				struct asus_xgm_info *info)
+{
+	size_t len = asus_report_len(hdev, FEATURE_KBD_LED_REPORT_ID2);
+	int ret;
+
+	if (!len)
+		return -EINVAL;
+
+	u8 *buf __free(kfree) = kzalloc(len, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	ret = asus_xgm_query(hdev, ASUS_XGM_QUERY_VERSION, buf, len);
+	if (ret < 0)
+		return ret;
+
+	if (len <= ASUS_XGM_RESP_HDR_LEN ||
+	    buf[ASUS_XGM_RESP_OPCODE] != ASUS_XGM_CMD_QUERY ||
+	    buf[ASUS_XGM_RESP_SUBCMD] != ASUS_XGM_QUERY_VERSION)
+		return -ENODEV;
+
+	asus_xgm_tlv_str(info->generation, sizeof(info->generation),
+			 buf, len, ASUS_XGM_TAG_GENERATION);
+	asus_xgm_tlv_str(info->firmware_version, sizeof(info->firmware_version),
+			 buf, len, ASUS_XGM_TAG_FIRMWARE);
+
+	return 0;
+}
+
+/**
+ * asus_xgm_drvdata() - Get the drvdata behind an XG Mobile attribute
+ * @dev: HID device the attribute is attached to
+ *
+ * Return: the asus_drvdata of @dev.
+ */
+static struct asus_drvdata *asus_xgm_drvdata(struct device *dev)
+{
+	return hid_get_drvdata(to_hid_device(dev));
+}
+
+static ssize_t xgm_model_show(struct device *dev,
+			      struct device_attribute *attr, char *buf)
+{
+	return sysfs_emit(buf, "%s\n", asus_xgm_drvdata(dev)->xgm_info->model);
+}
+static DEVICE_ATTR_RO(xgm_model);
+
+static ssize_t xgm_serial_show(struct device *dev,
+			       struct device_attribute *attr, char *buf)
+{
+	return sysfs_emit(buf, "%s\n", asus_xgm_drvdata(dev)->xgm_info->serial);
+}
+static DEVICE_ATTR_RO(xgm_serial);
+
+static ssize_t xgm_mainboard_show(struct device *dev,
+				  struct device_attribute *attr, char *buf)
+{
+	return sysfs_emit(buf, "%s\n", asus_xgm_drvdata(dev)->xgm_info->mainboard);
+}
+static DEVICE_ATTR_RO(xgm_mainboard);
+
+static ssize_t xgm_part_number_show(struct device *dev,
+				    struct device_attribute *attr, char *buf)
+{
+	return sysfs_emit(buf, "%s\n", asus_xgm_drvdata(dev)->xgm_info->part_number);
+}
+static DEVICE_ATTR_RO(xgm_part_number);
+
+static ssize_t xgm_firmware_version_show(struct device *dev,
+					 struct device_attribute *attr, char *buf)
+{
+	return sysfs_emit(buf, "%s\n", asus_xgm_drvdata(dev)->xgm_info->firmware_version);
+}
+static DEVICE_ATTR_RO(xgm_firmware_version);
+
+static ssize_t xgm_generation_show(struct device *dev,
+				   struct device_attribute *attr, char *buf)
+{
+	return sysfs_emit(buf, "%s\n", asus_xgm_drvdata(dev)->xgm_info->generation);
+}
+static DEVICE_ATTR_RO(xgm_generation);
+
+static struct attribute *asus_xgm_attrs[] = {
+	&dev_attr_xgm_model.attr,
+	&dev_attr_xgm_serial.attr,
+	&dev_attr_xgm_mainboard.attr,
+	&dev_attr_xgm_part_number.attr,
+	&dev_attr_xgm_firmware_version.attr,
+	&dev_attr_xgm_generation.attr,
+	NULL
+};
+
+static const struct attribute_group asus_xgm_attr_group = {
+	.attrs = asus_xgm_attrs,
+};
+
 static int asus_xgm_led_set(struct led_classdev *led_cdev, enum led_brightness value)
 {
 	const u8 buf[] = { FEATURE_KBD_LED_REPORT_ID2, 0xC5, (value) ? 0x50 : 0x00 };
@@ -5392,9 +5548,29 @@ static int asus_xgm_init(struct hid_device *hdev, struct asus_drvdata *drvdata)
 
 	drvdata->xgm_info = info;
 
+	ret = asus_xgm_get_version(hdev, info);
+	if (ret < 0)
+		hid_warn(hdev, "Failed to query XG Mobile version: %d\n", ret);
+	else
+		hid_info(hdev, "XG Mobile: firmware %s, generation %s\n",
+			 info->firmware_version, info->generation);
+
+	/*
+	 * The attribute group is not devm-managed: a creation failure is
+	 * fatal and unwound through asus_xgm_init_err, while on the unbind
+	 * path the removal is gated on xgm_info exactly like the creation.
+	 */
+	ret = sysfs_create_group(&hdev->dev.kobj, &asus_xgm_attr_group);
+	if (ret) {
+		hid_err(hdev, "Failed to create XG Mobile attributes: %d\n", ret);
+		goto asus_xgm_init_err;
+	}
+
 	drvdata->xgm_led = devm_kzalloc(&hdev->dev, sizeof(*drvdata->xgm_led), GFP_KERNEL);
-	if (drvdata->xgm_led == NULL)
-		return -ENOMEM;
+	if (!drvdata->xgm_led) {
+		ret = -ENOMEM;
+		goto asus_xgm_init_err;
+	}
 
 	name = devm_kasprintf(&hdev->dev, GFP_KERNEL, "asus:xgm-%s-%s:led",
 			      info->model,
@@ -5427,6 +5603,8 @@ static int asus_xgm_init(struct hid_device *hdev, struct asus_drvdata *drvdata)
 
 	return 0;
 asus_xgm_init_err:
+	sysfs_remove_group(&hdev->dev.kobj, &asus_xgm_attr_group);
+	drvdata->xgm_info = NULL;
 	drvdata->xgm_led = NULL;
 	return ret;
 }
@@ -5643,6 +5821,9 @@ static int asus_probe(struct hid_device *hdev, const struct hid_device_id *id)
 	if (drvdata->listener.brightness_set)
 		asus_hid_unregister_listener(&drvdata->listener);
 
+	if (drvdata->xgm_info)
+		sysfs_remove_group(&hdev->dev.kobj, &asus_xgm_attr_group);
+
 	if (drvdata->xgm_led)
 		devm_led_classdev_unregister(&hdev->dev, &drvdata->xgm_led->cdev);
 
@@ -5667,6 +5848,9 @@ static void asus_remove(struct hid_device *hdev)
 	if (drvdata->listener.brightness_set)
 		asus_hid_unregister_listener(&drvdata->listener);
 
+	if (drvdata->xgm_info)
+		sysfs_remove_group(&hdev->dev.kobj, &asus_xgm_attr_group);
+
 	if (drvdata->xgm_led)
 		devm_led_classdev_unregister(&hdev->dev, &drvdata->xgm_led->cdev);
 
-- 
2.47.3