linux-kernel - [PATCH] i2c-algo-bit: Added the bus lock during a i2c transaction

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Message-Id: <20250225113314.12353-1-anindya.sg@samsung.com>
Date: Tue, 25 Feb 2025 17:03:14 +0530
From: Anindya Sundar Gayen <anindya.sg@...sung.com>
To: andi.shyti@...nel.org, linux-i2c@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc: aswani.reddy@...sung.com, pankaj.dubey@...sung.com
Subject: [PATCH] i2c-algo-bit: Added the bus lock during a i2c transaction

Earlier i2c-bus lock was not available to i2c-algo-bit driver
for that reason if there are back to back i2c transaction occurs
it may be possible to occur a race condition.

To avoid the race condition we added a mutex lock mechanism which will
help to protect the i2c_outb()with a proper lock.

Signed-off-by: Anindya Sundar Gayen <anindya.sg@...sung.com>
---
 drivers/i2c/algos/i2c-algo-bit.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/i2c/algos/i2c-algo-bit.c b/drivers/i2c/algos/i2c-algo-bit.c
index eddf25b90ca8..18021dd9eef3 100644
--- a/drivers/i2c/algos/i2c-algo-bit.c
+++ b/drivers/i2c/algos/i2c-algo-bit.c
@@ -31,7 +31,7 @@
 #endif /* DEBUG */
 
 /* ----- global variables ---------------------------------------------	*/
-
+static DEFINE_MUTEX(i2c_bus_lock);
 static int bit_test;	/* see if the line-setting functions work	*/
 module_param(bit_test, int, S_IRUGO);
 MODULE_PARM_DESC(bit_test, "lines testing - 0 off; 1 report; 2 fail if stuck");
@@ -349,6 +349,8 @@ static int sendbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
 	int retval;
 	int wrcount = 0;
 
+	/* Aquire the lock before accessing the I2C bus */
+	mutex_lock(&i2c_bus_lock);
 	while (count > 0) {
 		retval = i2c_outb(i2c_adap, *temp);
 
@@ -379,6 +381,7 @@ static int sendbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
 			return retval;
 		}
 	}
+	mutex_unlock(&i2c_bus_lock);
 	return wrcount;
 }
 
-- 
2.17.1