HID: logitech-hidpp: prefix the name with "Logitech"

Current names are reported as "K750", "M705", and it can be misleading
for the users when they look at their input device list.

Prefixing the names with "Logitech " makes things better.

Signed-off-by: Benjamin Tissoires <[e-mail]>
Reviewed-by: Peter Wu <[e-mail]>
Signed-off-by: Jiri Kosina <[e-mail]>

drivers/hid/hid-logitech-hidpp.c

···
 		(report->rap.sub_id == 0x41);
 }
 
+/**
+ * hidpp_prefix_name() prefixes the current given name with "Logitech ".
+ */
+static void hidpp_prefix_name(char **name, int name_length)
+{
+#define PREFIX_LENGTH 9 /* "Logitech " */
+
+	int new_length;
+	char *new_name;
+
+	if (name_length > PREFIX_LENGTH &&
+	    strncmp(*name, "Logitech ", PREFIX_LENGTH) == 0)
+		/* The prefix has is already in the name */
+		return;
+
+	new_length = PREFIX_LENGTH + name_length;
+	new_name = kzalloc(new_length, GFP_KERNEL);
+	if (!new_name)
+		return;
+
+	snprintf(new_name, new_length, "Logitech %s", *name);
+
+	kfree(*name);
+
+	*name = new_name;
+}
+
 /* -------------------------------------------------------------------------- */
 /* HIDP++ 1.0 commands                                                        */
 /* -------------------------------------------------------------------------- */
···
 		return NULL;
 
 	memcpy(name, &response.rap.params[2], len);
+
+	/* include the terminating '\0' */
+	hidpp_prefix_name(&name, len + 1);
+
 	return name;
 }
 
···
 		}
 		index += ret;
 	}
+
+	/* include the terminating '\0' */
+	hidpp_prefix_name(&name, __name_length + 1);
 
 	return name;
 }