Input: zinitix - read and cache device version numbers

The chip hardware revision, firmware version and regdata
revision is needed to discern because for example touchkeys
are handled by different registers on different versions of
the chip. Example output from BT404:

Zinitix-TS 3-0020: chip revision 4040 firmware version 0088
  regdata version 0004

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20240830-zinitix-tk-versions-v2-1-90eae6817eda@linaro.org
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Author: Linus Walleij

drivers/input/touchscreen/zinitix.c

@@ -150,6 +150,10 @@ struct bt541_ts_data {
 	u32 zinitix_mode;
 	u32 keycodes[MAX_SUPPORTED_BUTTON_NUM];
 	int num_keycodes;
+	bool have_versioninfo;
+	u16 chip_revision;
+	u16 firmware_version;
+	u16 regdata_version;
 };
 
 static int zinitix_read_data(struct i2c_client *client,
@@ -194,6 +198,19 @@ static int zinitix_write_cmd(struct i2c_client *client, u16 reg)
 	return 0;
 }
 
+static u16 zinitix_get_u16_reg(struct bt541_ts_data *bt541, u16 vreg)
+{
+	struct i2c_client *client = bt541->client;
+	int error;
+	__le16 val;
+
+	error = zinitix_read_data(client, vreg, (void *)&val, 2);
+	if (error)
+		return U8_MAX;
+
+	return le16_to_cpu(val);
+}
+
 static int zinitix_init_touch(struct bt541_ts_data *bt541)
 {
 	struct i2c_client *client = bt541->client;
@@ -207,6 +224,25 @@ static int zinitix_init_touch(struct bt541_ts_data *bt541)
 		return error;
 	}
 
+	/*
+	 * Read and cache the chip revision and firmware version the first time
+	 * we get here.
+	 */
+	if (!bt541->have_versioninfo) {
+		bt541->chip_revision = zinitix_get_u16_reg(bt541,
+						ZINITIX_CHIP_REVISION);
+		bt541->firmware_version = zinitix_get_u16_reg(bt541,
+						ZINITIX_FIRMWARE_VERSION);
+		bt541->regdata_version = zinitix_get_u16_reg(bt541,
+						ZINITIX_DATA_VERSION_REG);
+		bt541->have_versioninfo = true;
+
+		dev_dbg(&client->dev,
+			"chip revision %04x firmware version %04x regdata version %04x\n",
+			bt541->chip_revision, bt541->firmware_version,
+			bt541->regdata_version);
+	}
+
 	error = zinitix_write_u16(client, ZINITIX_INT_ENABLE_FLAG, 0x0);
 	if (error) {
 		dev_err(&client->dev,