[PATCH 2/5] HID: hid-lenovo-go: fix the FPS mode DPI request

[Aditya Dash <mradityadash@gmail.com>]

mcu_property_out() adds the five-byte request header used by most
configuration commands. For FPS mode DPI writes, this inserts a device byte
before the four-byte DPI value.

The FPS mode DPI request does not contain a device byte. Its little-endian
DPI value starts immediately after the command and sub-command.

Use the four-byte header only for FPS mode DPI writes. Keep the common
header for all other requests.

Fixes: f0bedee60607 ("HID: hid-lenovo-go: Add FPS Mode DPI settings")
Assisted-by: Pi:gpt-5.6-sol
Signed-off-by: Aditya Dash <mradityadash@gmail.com>
---
The corrected FPS mode DPI write was not tested on hardware.

 drivers/hid/hid-lenovo-go.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/hid/hid-lenovo-go.c b/drivers/hid/hid-lenovo-go.c
index b8248bf8965c..a6e9a130ad41 100644
--- a/drivers/hid/hid-lenovo-go.c
+++ b/drivers/hid/hid-lenovo-go.c
@@ -725,6 +725,11 @@ static int mcu_property_out(struct hid_device *hdev, u8 id, u8 command,
 	int timeout = 50;
 	int ret;
 
+	/* The FPS mode DPI request does not contain a device byte. */
+	if (id == MCU_CONFIG_DATA && command == SET_DPI_CFG &&
+	    index == FPS_MODE_DPI)
+		header_size--;
+
 	if (header_size + len > GO_PACKET_SIZE)
 		return -EINVAL;
 
-- 
2.55.0