Adds command to probe for the MCU ID of the Lenovo Legion Go S
Controller and assign it to a device attribute.

Reviewed-by: Mark Pearson <mpearson-lenovo@squebb.ca>
Signed-off-by: Derek J. Clark <derekjohn.clark@gmail.com>
---
v6:
  - Use NULL instead of 0 in mcu_propery_out when there is no data.
---
 drivers/hid/hid-lenovo-go-s.c | 56 +++++++++++++++++++++++++++++++++++
 1 file changed, 56 insertions(+)

diff --git a/drivers/hid/hid-lenovo-go-s.c b/drivers/hid/hid-lenovo-go-s.c
index c9f57dfa145a..8ee75f724b5b 100644
--- a/drivers/hid/hid-lenovo-go-s.c
+++ b/drivers/hid/hid-lenovo-go-s.c
@@ -18,6 +18,7 @@
 #include <linux/mutex.h>
 #include <linux/printk.h>
 #include <linux/string.h>
+#include <linux/sysfs.h>
 #include <linux/types.h>
 #include <linux/unaligned.h>
 #include <linux/usb.h>
@@ -34,8 +35,13 @@ static struct hid_gos_cfg {
 	struct completion send_cmd_complete;
 	struct hid_device *hdev;
 	struct mutex cfg_mutex; /*ensure single synchronous output report*/
+	u8 mcu_id[12];
 } drvdata;
 
+struct gos_cfg_attr {
+	u8 index;
+};
+
 struct command_report {
 	u8 cmd;
 	u8 sub_cmd;
@@ -70,6 +76,14 @@ static int hid_gos_version_event(u8 *data)
 	return 0;
 }
 
+static int hid_gos_mcu_id_event(struct command_report *cmd_rep)
+{
+	drvdata.mcu_id[0] = cmd_rep->sub_cmd;
+	memcpy(&drvdata.mcu_id[1], cmd_rep->data, 11);
+
+	return 0;
+}
+
 static int get_endpoint_address(struct hid_device *hdev)
 {
 	struct usb_interface *intf = to_usb_interface(hdev->dev.parent);
@@ -103,6 +117,9 @@ static int hid_gos_raw_event(struct hid_device *hdev, struct hid_report *report,
 	case GET_VERSION:
 		ret = hid_gos_version_event(data);
 		break;
+	case GET_MCU_ID:
+		ret = hid_gos_mcu_id_event(cmd_rep);
+		break;
 	default:
 		ret = -EINVAL;
 		break;
@@ -157,10 +174,41 @@ static int mcu_property_out(struct hid_device *hdev, u8 command, u8 index,
 	return 0;
 }
 
+static ssize_t mcu_id_show(struct device *dev, struct device_attribute *attr,
+			   char *buf)
+{
+	return sysfs_emit(buf, "%*phN\n", 12, &drvdata.mcu_id);
+}
+
+/* MCU */
+static DEVICE_ATTR_RO(mcu_id);
+
+static struct attribute *legos_mcu_attrs[] = {
+	&dev_attr_mcu_id.attr,
+	NULL,
+};
+
+static const struct attribute_group mcu_attr_group = {
+	.attrs = legos_mcu_attrs,
+};
+
+static const struct attribute_group *top_level_attr_groups[] = {
+	&mcu_attr_group,
+	NULL,
+};
+
 static void cfg_setup(struct work_struct *work)
 {
 	int ret;
 
+	/* MCU */
+	ret = mcu_property_out(drvdata.hdev, GET_MCU_ID, FEATURE_NONE, NULL, 0);
+	if (ret) {
+		dev_err(&drvdata.hdev->dev, "Failed to retrieve MCU ID: %i\n",
+			ret);
+		return;
+	}
+
 	ret = mcu_property_out(drvdata.hdev, GET_VERSION, FEATURE_NONE, NULL, 0);
 	if (ret) {
 		dev_err(&drvdata.hdev->dev, "Failed to retrieve MCU Version: %i\n", ret);
@@ -177,6 +225,13 @@ static int hid_gos_cfg_probe(struct hid_device *hdev,
 	drvdata.hdev = hdev;
 	mutex_init(&drvdata.cfg_mutex);
 
+	ret = sysfs_create_groups(&hdev->dev.kobj, top_level_attr_groups);
+	if (ret) {
+		dev_err_probe(&hdev->dev, ret,
+			      "Failed to create gamepad configuration attributes\n");
+		return ret;
+	}
+
 	init_completion(&drvdata.send_cmd_complete);
 
 	/* Executing calls prior to returning from probe will lock the MCU. Schedule
@@ -196,6 +251,7 @@ static void hid_gos_cfg_remove(struct hid_device *hdev)
 {
 	guard(mutex)(&drvdata.cfg_mutex);
 	cancel_delayed_work_sync(&drvdata.gos_cfg_setup);
+	sysfs_remove_groups(&hdev->dev.kobj, top_level_attr_groups);
 	hid_hw_close(hdev);
 	hid_hw_stop(hdev);
 	hid_set_drvdata(hdev, NULL);
-- 
2.53.0