[PATCH 1/2] Input: ilitek_ts: add stylus input support
From: Kristian Mide
Date: Fri Jun 26 2026 - 17:45:06 EST
Add a separate stylus input device for report ID 0x0c packets,
with pressure, hover, and side-button support.
The pen device is created lazily on first pen report so
touchscreen-only hardware does not expose stylus capabilities up
front.
The packet format is reverse engineered from a tested CHUWI
Hi10 Max. Pressure is reported from buf[6..7] shifted right by
one, matching the observed 1024 pressure levels on the tested
device.
Pen coordinates are reported through touchscreen_report_pos()
so the same axis inversion and swapping properties used by the
touch path apply to the stylus as well.
---
drivers/input/touchscreen/ilitek_ts_i2c.c | 130 ++++++++++++++++++++++
1 file changed, 130 insertions(+)
diff --git a/drivers/input/touchscreen/ilitek_ts_i2c.c b/drivers/input/touchscreen/ilitek_ts_i2c.c
index 3de0fbf8d..f0721af02 100644
--- a/drivers/input/touchscreen/ilitek_ts_i2c.c
+++ b/drivers/input/touchscreen/ilitek_ts_i2c.c
@@ -18,6 +18,7 @@
#include <linux/gpio/consumer.h>
#include <linux/errno.h>
#include <linux/acpi.h>
+#include <linux/device/devres.h>
#include <linux/input/touchscreen.h>
#include <linux/unaligned.h>
@@ -37,6 +38,18 @@
#define ILITEK_TP_CMD_GET_IC_MODE 0xC0
#define ILITEK_TP_I2C_REPORT_ID 0x48
+/* Reverse engineered stylus report on a tested CHUWI Hi10 Max device. */
+#define ILITEK_PEN_I2C_REPORT_ID 0x0C
+#define ILITEK_PEN_PRESSURE_MAX 1023
+#define ILITEK_PEN_DISTANCE_MAX 2
+/* Userspace expects tablet axis resolution; with INPUT_PROP_DIRECT this is */
+/* mostly descriptive and does not materially affect event coordinates. */
+#define ILITEK_PEN_RESOLUTION 68
+
+#define ILITEK_PEN_FLAG_TOUCH 0x01
+#define ILITEK_PEN_FLAG_STYLUS2 0x02
+#define ILITEK_PEN_FLAG_STYLUS 0x08
+#define ILITEK_PEN_FLAG_PROX 0x10
#define REPORT_COUNT_ADDRESS 61
#define ILITEK_SUPPORT_MAX_POINT 40
@@ -50,6 +63,7 @@ struct ilitek_ts_data {
struct i2c_client *client;
struct gpio_desc *reset_gpio;
struct input_dev *input_dev;
+ struct input_dev *pen_input_dev;
struct touchscreen_properties prop;
const struct ilitek_protocol_map *ptl_cb_func;
@@ -89,6 +103,9 @@ enum ilitek_cmds {
MAX_CMD_CNT
};
+static int ilitek_pen_input_dev_init(struct device *dev,
+ struct ilitek_ts_data *ts);
+
/* ILITEK I2C R/W APIs */
static int ilitek_i2c_write_and_read(struct ilitek_ts_data *ts,
u8 *cmd, int write_len, int delay,
@@ -146,6 +163,62 @@ static void ilitek_touch_down(struct ilitek_ts_data *ts, unsigned int id,
touchscreen_report_pos(input, &ts->prop, x, y, true);
}
+static void ilitek_unregister_pen_input(void *data)
+{
+ struct ilitek_ts_data *ts = data;
+
+ input_unregister_device(ts->pen_input_dev);
+ ts->pen_input_dev = NULL;
+}
+
+/*
+ * buf[1] carries prox/touch/side-button state and buf[6..7] carries
+ * pressure. A right shift by one matches the observed 1024 pressure levels.
+ */
+static int ilitek_process_pen_report(struct ilitek_ts_data *ts, u8 *buf)
+{
+ struct device *dev = &ts->client->dev;
+ struct input_dev *input = ts->pen_input_dev;
+ unsigned int x, y, z, distance;
+ bool prox, touch, stylus, stylus2;
+ int error;
+
+ if (!input) {
+ error = ilitek_pen_input_dev_init(dev, ts);
+ if (error) {
+ dev_err_ratelimited(dev,
+ "failed to register pen input device: %d\n",
+ error);
+ return 0;
+ }
+ input = ts->pen_input_dev;
+ }
+
+ x = get_unaligned_le16(buf + 2);
+ y = get_unaligned_le16(buf + 4);
+ z = get_unaligned_le16(buf + 6) >> 1;
+ prox = !!(buf[1] & ILITEK_PEN_FLAG_PROX);
+ touch = !!(buf[1] & ILITEK_PEN_FLAG_TOUCH);
+ stylus = !!(buf[1] & ILITEK_PEN_FLAG_STYLUS);
+ stylus2 = !!(buf[1] & ILITEK_PEN_FLAG_STYLUS2);
+ distance = prox ? (touch ? 0 : 1) : ILITEK_PEN_DISTANCE_MAX;
+ if (!touch)
+ z = 0;
+ else if (z > ILITEK_PEN_PRESSURE_MAX)
+ z = ILITEK_PEN_PRESSURE_MAX;
+
+ input_report_key(input, BTN_TOOL_PEN, prox || touch);
+ input_report_key(input, BTN_TOUCH, touch);
+ input_report_key(input, BTN_STYLUS, stylus);
+ input_report_key(input, BTN_STYLUS2, stylus2);
+ touchscreen_report_pos(input, &ts->prop, x, y, false);
+ input_report_abs(input, ABS_PRESSURE, z);
+ input_report_abs(input, ABS_DISTANCE, distance);
+ input_sync(input);
+
+ return 0;
+}
+
static int ilitek_process_and_report_v6(struct ilitek_ts_data *ts)
{
int error = 0;
@@ -164,6 +237,9 @@ static int ilitek_process_and_report_v6(struct ilitek_ts_data *ts)
return error;
}
+ if (buf[0] == ILITEK_PEN_I2C_REPORT_ID)
+ return ilitek_process_pen_report(ts, buf);
+
if (buf[0] != ILITEK_TP_I2C_REPORT_ID) {
dev_err(dev, "get touch info failed. Wrong id: 0x%02X\n", buf[0]);
return -EINVAL;
@@ -459,6 +535,60 @@ static int ilitek_read_tp_info(struct ilitek_ts_data *ts, bool boot)
return 0;
}
+static int ilitek_pen_input_dev_init(struct device *dev, struct ilitek_ts_data *ts)
+{
+ struct input_dev *pen_input;
+ int error;
+
+ if (ts->pen_input_dev)
+ return 0;
+
+ /* No explicit pen capability probe is known; create on first pen report. */
+
+ pen_input = input_allocate_device();
+ if (!pen_input)
+ return -ENOMEM;
+
+ ts->pen_input_dev = pen_input;
+ pen_input->dev.parent = dev;
+ pen_input->name = "ilitek_ts_pen";
+ pen_input->id.bustype = BUS_I2C;
+
+ __set_bit(INPUT_PROP_DIRECT, pen_input->propbit);
+ __set_bit(EV_KEY, pen_input->evbit);
+ __set_bit(EV_ABS, pen_input->evbit);
+ __set_bit(BTN_TOUCH, pen_input->keybit);
+ __set_bit(BTN_TOOL_PEN, pen_input->keybit);
+ __set_bit(BTN_STYLUS, pen_input->keybit);
+ __set_bit(BTN_STYLUS2, pen_input->keybit);
+
+ input_set_abs_params(pen_input, ABS_X,
+ ts->screen_min_x, ts->screen_max_x, 0, 0);
+ input_set_abs_params(pen_input, ABS_Y,
+ ts->screen_min_y, ts->screen_max_y, 0, 0);
+ input_set_abs_params(pen_input, ABS_PRESSURE, 0,
+ ILITEK_PEN_PRESSURE_MAX, 0, 0);
+ input_set_abs_params(pen_input, ABS_DISTANCE, 0,
+ ILITEK_PEN_DISTANCE_MAX, 0, 0);
+ input_abs_set_res(pen_input, ABS_X, ILITEK_PEN_RESOLUTION);
+ input_abs_set_res(pen_input, ABS_Y, ILITEK_PEN_RESOLUTION);
+
+ error = input_register_device(pen_input);
+ if (error)
+ goto err_free_pen_input;
+
+ error = devm_add_action_or_reset(dev, ilitek_unregister_pen_input, ts);
+ if (error)
+ return error;
+
+ return 0;
+
+err_free_pen_input:
+ ts->pen_input_dev = NULL;
+ input_free_device(pen_input);
+ return error;
+}
+
static int ilitek_input_dev_init(struct device *dev, struct ilitek_ts_data *ts)
{
int error;
--
2.54.0