linux-kernel - [PATCH] i2c: amd756: Fix endianness handling for word data

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Message-Id: <20241227132250.14435-1-evepolonium@gmail.com>
Date: Fri, 27 Dec 2024 18:52:49 +0530
From: Atharva Tiwari <evepolonium@...il.com>
To: 
Cc: evepolonium@...il.com,
	Jean Delvare <jdelvare@...e.com>,
	Andi Shyti <andi.shyti@...nel.org>,
	linux-i2c@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] i2c: amd756: Fix endianness handling for word data

Ensure correct handling of "endianness"
for word-sized data in amd756_access

 - Convert word data into little-endian using cpu_to_le16
 - Convert word data from little-endian 
   to cpu native format using le16_to_cpu

This fixes poteential issues on big-endian systems and
ensure proper byte ordering for SMBus word transacitions

Signed-off-by: Atharva Tiwari <evepolonium@...il.com>
---
 drivers/i2c/busses/i2c-amd756.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/i2c/busses/i2c-amd756.c b/drivers/i2c/busses/i2c-amd756.c
index fa0d5a2c3732..f6fe4c32af04 100644
--- a/drivers/i2c/busses/i2c-amd756.c
+++ b/drivers/i2c/busses/i2c-amd756.c
@@ -31,6 +31,7 @@
 #include <linux/i2c.h>
 #include <linux/acpi.h>
 #include <linux/io.h>
+#include <linux/byteorder/generic.h>
 
 /* AMD756 SMBus address offsets */
 #define SMB_ADDR_OFFSET		0xE0
@@ -211,7 +212,7 @@ static s32 amd756_access(struct i2c_adapter * adap, u16 addr,
 		       SMB_HOST_ADDRESS);
 		outb_p(command, SMB_HOST_COMMAND);
 		if (read_write == I2C_SMBUS_WRITE)
-			outw_p(data->word, SMB_HOST_DATA);	/* TODO: endian???? */
+			outw_p(cpu_to_le16(data->word), SMB_HOST_DATA);
 		size = AMD756_WORD_DATA;
 		break;
 	case I2C_SMBUS_BLOCK_DATA:
@@ -256,7 +257,7 @@ static s32 amd756_access(struct i2c_adapter * adap, u16 addr,
 		data->byte = inw_p(SMB_HOST_DATA);
 		break;
 	case AMD756_WORD_DATA:
-		data->word = inw_p(SMB_HOST_DATA);	/* TODO: endian???? */
+		data->word = le16_to_cpu(inw_p(SMB_HOST_DATA));
 		break;
 	case AMD756_BLOCK_DATA:
 		data->block[0] = inw_p(SMB_HOST_DATA) & 0x3f;
-- 
2.39.5