Input: silead - add pen support

Some Silead touchscreens have support for an active (battery powered)
pen, add support for this.

So far pen-support has only been seen on X86/ACPI (non devicetree) devs,
IOW it is not used in actual devicetree files. The devicetree-bindings
maintainers have requested properties like these to not be added to the
devicetree-bindings, so the new properties are deliberately not added
to the existing silead devicetree-bindings documentation.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20211122220637.11386-3-hdegoede@redhat.comSigned-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/touchscreen/silead.c

@@ -67,6 +67,7 @@ struct silead_ts_data {
 	struct i2c_client *client;
 	struct gpio_desc *gpio_power;
 	struct input_dev *input;
+	struct input_dev *pen_input;
 	struct regulator_bulk_data regulators[2];
 	char fw_name[64];
 	struct touchscreen_properties prop;
@@ -77,6 +78,11 @@ struct silead_ts_data {
 	int id[SILEAD_MAX_FINGERS];
 	u32 efi_fw_min_max[4];
 	bool efi_fw_min_max_set;
+	bool pen_supported;
+	bool pen_down;
+	u32 pen_x_res;
+	u32 pen_y_res;
+	int pen_up_count;
 };
 
 struct silead_fw_data {
@@ -144,6 +150,40 @@ static int silead_ts_request_input_dev(struct silead_ts_data *data)
 	error = input_register_device(data->input);
 	if (error) {
 		dev_err(dev, "Failed to register input device: %d\n", error);
+			return error;
+	}
+
+	return 0;
+}
+
+static int silead_ts_request_pen_input_dev(struct silead_ts_data *data)
+{
+	struct device *dev = &data->client->dev;
+	int error;
+
+	if (!data->pen_supported)
+		return 0;
+
+	data->pen_input = devm_input_allocate_device(dev);
+	if (!data->pen_input)
+		return -ENOMEM;
+
+	input_set_abs_params(data->pen_input, ABS_X, 0, 4095, 0, 0);
+	input_set_abs_params(data->pen_input, ABS_Y, 0, 4095, 0, 0);
+	input_set_capability(data->pen_input, EV_KEY, BTN_TOUCH);
+	input_set_capability(data->pen_input, EV_KEY, BTN_TOOL_PEN);
+	set_bit(INPUT_PROP_DIRECT, data->pen_input->propbit);
+	touchscreen_parse_properties(data->pen_input, false, &data->prop);
+	input_abs_set_res(data->pen_input, ABS_X, data->pen_x_res);
+	input_abs_set_res(data->pen_input, ABS_Y, data->pen_y_res);
+
+	data->pen_input->name = SILEAD_TS_NAME " pen";
+	data->pen_input->phys = "input/pen";
+	data->input->id.bustype = BUS_I2C;
+
+	error = input_register_device(data->pen_input);
+	if (error) {
+		dev_err(dev, "Failed to register pen input device: %d\n", error);
 		return error;
 	}
 
@@ -161,6 +201,45 @@ static void silead_ts_set_power(struct i2c_client *client,
 	}
 }
 
+static bool silead_ts_handle_pen_data(struct silead_ts_data *data, u8 *buf)
+{
+	u8 *coord = buf + SILEAD_POINT_DATA_LEN;
+	struct input_mt_pos pos;
+
+	if (!data->pen_supported || buf[2] != 0x00 || buf[3] != 0x00)
+		return false;
+
+	if (buf[0] == 0x00 && buf[1] == 0x00 && data->pen_down) {
+		data->pen_up_count++;
+		if (data->pen_up_count == 6) {
+			data->pen_down = false;
+			goto sync;
+		}
+		return true;
+	}
+
+	if (buf[0] == 0x01 && buf[1] == 0x08) {
+		touchscreen_set_mt_pos(&pos, &data->prop,
+			get_unaligned_le16(&coord[SILEAD_POINT_X_OFF]) & 0xfff,
+			get_unaligned_le16(&coord[SILEAD_POINT_Y_OFF]) & 0xfff);
+
+		input_report_abs(data->pen_input, ABS_X, pos.x);
+		input_report_abs(data->pen_input, ABS_Y, pos.y);
+
+		data->pen_up_count = 0;
+		data->pen_down = true;
+		goto sync;
+	}
+
+	return false;
+
+sync:
+	input_report_key(data->pen_input, BTN_TOOL_PEN, data->pen_down);
+	input_report_key(data->pen_input, BTN_TOUCH, data->pen_down);
+	input_sync(data->pen_input);
+	return true;
+}
+
 static void silead_ts_read_data(struct i2c_client *client)
 {
 	struct silead_ts_data *data = i2c_get_clientdata(client);
@@ -183,6 +262,9 @@ static void silead_ts_read_data(struct i2c_client *client)
 		buf[0] = data->max_fingers;
 	}
 
+	if (silead_ts_handle_pen_data(data, buf))
+		goto sync; /* Pen is down, release all previous touches */
+
 	touch_nr = 0;
 	bufp = buf + SILEAD_POINT_DATA_LEN;
 	for (i = 0; i < buf[0]; i++, bufp += SILEAD_POINT_DATA_LEN) {
@@ -225,6 +307,7 @@ static void silead_ts_read_data(struct i2c_client *client)
 			data->pos[i].y, data->id[i], data->slots[i]);
 	}
 
+sync:
 	input_mt_sync_frame(input);
 	input_report_key(input, KEY_LEFTMETA, softbutton_pressed);
 	input_sync(input);
@@ -356,6 +439,14 @@ static int silead_ts_load_fw(struct i2c_client *client)
 						       ARRAY_SIZE(data->efi_fw_min_max));
 		if (!error)
 			data->efi_fw_min_max_set = true;
+
+		/* The EFI (platform) embedded fw does not have pen support */
+		if (data->pen_supported) {
+			dev_warn(dev, "Warning loading '%s' from filesystem failed, using EFI embedded copy.\n",
+				 data->fw_name);
+			dev_warn(dev, "Warning pen support is known to be broken in the EFI embedded fw version\n");
+			data->pen_supported = false;
+		}
 	}
 
 	fw_size = fw->size / sizeof(*fw_data);
@@ -513,6 +604,10 @@ static void silead_ts_read_props(struct i2c_client *client)
 			 "silead/%s", str);
 	else
 		dev_dbg(dev, "Firmware file name read error. Using default.");
+
+	data->pen_supported = device_property_read_bool(dev, "silead,pen-supported");
+	device_property_read_u32(dev, "silead,pen-resolution-x", &data->pen_x_res);
+	device_property_read_u32(dev, "silead,pen-resolution-y", &data->pen_y_res);
 }
 
 #ifdef CONFIG_ACPI
@@ -625,6 +720,10 @@ static int silead_ts_probe(struct i2c_client *client,
 	if (error)
 		return error;
 
+	error = silead_ts_request_pen_input_dev(data);
+	if (error)
+		return error;
+
 	error = devm_request_threaded_irq(dev, client->irq,
 					  NULL, silead_ts_threaded_irq_handler,
 					  IRQF_ONESHOT, client->name, data);