mfd: qnap-mcu: Calculate the checksum on the actual number of bytes received

In the case of an error message, the number of received bytes can be
less than originally expected but still contain a valid message.

If the transfer itself ended in an error we would exit earlier already.

So calculate the checksum on the number of received bytes and not the
number of expected bytes.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://patch.msgid.link/20251113165218.449616-2-heiko@sntech.de
Signed-off-by: Lee Jones <lee@kernel.org>

diff --git a/drivers/mfd/qnap-mcu.c b/drivers/mfd/qnap-mcu.c
index 4ec1f4cf902f60e518be085273fa936a093bc6b8..4cd5319fc6cb0587f106676fd3c970ed16f50afa 100644 (file)
--- a/drivers/mfd/qnap-mcu.c
+++ b/drivers/mfd/qnap-mcu.c
@@ -175,8 +175,8 @@ int qnap_mcu_exec(struct qnap_mcu *mcu,
                return -ETIMEDOUT;
        }
 
-       crc = qnap_mcu_csum(rx, reply_data_size);
-       if (crc != rx[reply_data_size]) {
+       crc = qnap_mcu_csum(rx, reply->received - QNAP_MCU_CHECKSUM_SIZE);
+       if (crc != rx[reply->received - QNAP_MCU_CHECKSUM_SIZE]) {
                dev_err(&mcu->serdev->dev, "Invalid Checksum received\n");
                return -EIO;
        }