Input: exc3000 - add type sysfs attribute

Add a sysfs attribute to query the type of the touchscreen device.
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Link: https://lore.kernel.org/r/20210125182527.1225245-5-l.stach@pengutronix.deSigned-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Documentation/ABI/testing/sysfs-driver-input-exc3000

@@ -15,3 +15,12 @@ Description:    Reports the model identification provided by the touchscreen, fo
 		Access: Read
 
 		Valid values: Represented as string
+
+What:		/sys/bus/i2c/devices/xxx/type
+Date:		Jan 2021
+Contact:	linux-input@vger.kernel.org
+Description:	Reports the type identification provided by the touchscreen, for example "PCAP82H80 Series"
+
+		Access: Read
+
+		Valid values: Represented as string

drivers/input/touchscreen/exc3000.c

@@ -301,9 +301,26 @@ static ssize_t model_show(struct device *dev,
 }
 static DEVICE_ATTR_RO(model);
 
+static ssize_t type_show(struct device *dev,
+			  struct device_attribute *attr, char *buf)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct exc3000_data *data = i2c_get_clientdata(client);
+	u8 response[EXC3000_LEN_FRAME];
+	int ret;
+
+	ret = exc3000_vendor_data_request(data, (u8[]){'F'}, 1, response, 1);
+	if (ret < 0)
+		return ret;
+
+	return sprintf(buf, "%s\n", &response[1]);
+}
+static DEVICE_ATTR_RO(type);
+
 static struct attribute *sysfs_attrs[] = {
 	&dev_attr_fw_version.attr,
 	&dev_attr_model.attr,
+	&dev_attr_type.attr,
 	NULL
 };