linux-kernel - [PATCH] i2c: i801: Fix a refactoring that broke a touchpad on Lenovo P1

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Date: Thu, 21 Mar 2024 10:19:19 -0400
From: Maxim Levitsky <mlevitsk@...hat.com>
To: linux-kernel@...r.kernel.org
Cc: Jean Delvare <jdelvare@...e.com>,
	Andi Shyti <andi.shyti@...nel.org>,
	Heiner Kallweit <hkallweit1@...il.com>,
	linux-i2c@...r.kernel.org,
	Maxim Levitsky <mlevitsk@...hat.com>
Subject: [PATCH] i2c: i801: Fix a refactoring that broke a touchpad on Lenovo P1

Commit 857cc04cdf50 ("i2c: i801: Add helper i801_get_block_len")
introduced a slight functional change: the status variable is now
overwritten with the length of an SMBUS tranasaction,
even in case of success.

This breaks the touchpad on at least my Lenovo P1:

rmi4_physical rmi4-00: Read PDT entry at 0x00e9 failed, code: -6.
rmi4_physical rmi4-00: RMI initial reset failed! Continuing in spite of this.
rmi4_physical rmi4-00: Read PDT entry at 0x00e9 failed, code: -6.
rmi4_physical rmi4-00: IRQ counting failed with code -6.

Fixes: 857cc04cdf50 ("i2c: i801: Add helper i801_get_block_len")

Signed-off-by: Maxim Levitsky <mlevitsk@...hat.com>
---
 drivers/i2c/busses/i2c-i801.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/i2c/busses/i2c-i801.c b/drivers/i2c/busses/i2c-i801.c
index a6861660cb8c..79870dd7a014 100644
--- a/drivers/i2c/busses/i2c-i801.c
+++ b/drivers/i2c/busses/i2c-i801.c
@@ -536,11 +536,12 @@ static int i801_block_transaction_by_block(struct i801_priv *priv,
 
 	if (read_write == I2C_SMBUS_READ ||
 	    command == I2C_SMBUS_BLOCK_PROC_CALL) {
-		status = i801_get_block_len(priv);
-		if (status < 0)
+		len = i801_get_block_len(priv);
+		if (len < 0) {
+			status = len;
 			goto out;
+		}
 
-		len = status;
 		data->block[0] = len;
 		inb_p(SMBHSTCNT(priv));	/* reset the data buffer index */
 		for (i = 0; i < len; i++)
-- 
2.40.1