[PATCH v4 2/2] Input: ilitek_ts_i2c - add report id message validation

[Francesco Dolcini <francesco@dolcini.it>]

From: Emanuele Ghidoli <emanuele.ghidoli@toradex.com>

Ilitek touch IC driver answer to plain i2c read request, after it has
generated an interrupt request, with a report id message starting
with an identifier and a series of points.
If a request is sent unsolicited by an interrupt request the answer
do not contain this identifier.
Add a test to discard these messages, making the driver robust to
spurious interrupt requests.

Fixes: 42370681bd46 ("Input: Add support for ILITEK Lego Series")
Signed-off-by: Emanuele Ghidoli <emanuele.ghidoli@toradex.com>
Signed-off-by: Francesco Dolcini <francesco.dolcini@toradex.com>
---
v4:
 - just return in case of error
 - removed reviewed by

v3: https://lore.kernel.org/all/20231222183114.30775-1-francesco@dolcini.it/
 - series taken over from Emanuele to Francesco and resent

v2: https://lore.kernel.org/all/20230920074650.922292-1-ghidoliemanuele@gmail.com/
 - first version

v1: not existing, patch was initially sent as v2 by mistake
---
 drivers/input/touchscreen/ilitek_ts_i2c.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/input/touchscreen/ilitek_ts_i2c.c b/drivers/input/touchscreen/ilitek_ts_i2c.c
index e1849185e18c..5a807ad72319 100644
--- a/drivers/input/touchscreen/ilitek_ts_i2c.c
+++ b/drivers/input/touchscreen/ilitek_ts_i2c.c
@@ -37,6 +37,8 @@
 #define ILITEK_TP_CMD_GET_MCU_VER			0x61
 #define ILITEK_TP_CMD_GET_IC_MODE			0xC0
 
+#define ILITEK_TP_I2C_REPORT_ID				0x48
+
 #define REPORT_COUNT_ADDRESS				61
 #define ILITEK_SUPPORT_MAX_POINT			40
 
@@ -163,6 +165,11 @@ static int ilitek_process_and_report_v6(struct ilitek_ts_data *ts)
 		return error;
 	}
 
+	if (buf[0] != ILITEK_TP_I2C_REPORT_ID) {
+		dev_err(dev, "get touch info failed. Wrong id: 0x%02X\n", buf[0]);
+		return -EINVAL;
+	}
+
 	report_max_point = buf[REPORT_COUNT_ADDRESS];
 	if (report_max_point > ts->max_tp) {
 		dev_err(dev, "FW report max point:%d > panel info. max:%d\n",
-- 
2.39.2