From: Conor Dooley <conor.dooley@microchip.com>

Introducing support for smbus re-broke i2cdetect, causing it to detect
devices at every i2c address, just as it did prior to being fixed in
commit 49e1f0fd0d4cb ("i2c: microchip-core: fix "ghost" detections").
This was caused by an oversight, where the new smbus code failed to
check the return value of mchp_corei2c_xfer(). Check it, and propagate
any errors.

Fixes: d6ceb40538263 ("i2c: microchip-corei2c: add smbus support")
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
---
v3:
- actually set ret before returning it, not whatever my debug code was
  doing...

v2:
- replace "if (ret)" with "if (ret < 0)" because the xfer callback,
  which the smbus code re-uses, can return positive numbers in success
  cases.

CC: Conor Dooley <conor.dooley@microchip.com>
CC: Daire McNamara <daire.mcnamara@microchip.com>
CC: Andi Shyti <andi.shyti@kernel.org>
CC: linux-i2c@vger.kernel.org
CC: linux-kernel@vger.kernel.org
---
 drivers/i2c/busses/i2c-microchip-corei2c.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/i2c/busses/i2c-microchip-corei2c.c b/drivers/i2c/busses/i2c-microchip-corei2c.c
index 492bf4c34722c..2be9e8c720b10 100644
--- a/drivers/i2c/busses/i2c-microchip-corei2c.c
+++ b/drivers/i2c/busses/i2c-microchip-corei2c.c
@@ -435,6 +435,7 @@ static int mchp_corei2c_smbus_xfer(struct i2c_adapter *adap, u16 addr, unsigned
 	u8 tx_buf[I2C_SMBUS_BLOCK_MAX + 2];
 	u8 rx_buf[I2C_SMBUS_BLOCK_MAX + 1];
 	int num_msgs = 1;
+	int ret;
 
 	msgs[CORE_I2C_SMBUS_MSG_WR].addr = addr;
 	msgs[CORE_I2C_SMBUS_MSG_WR].flags = 0;
@@ -505,7 +506,10 @@ static int mchp_corei2c_smbus_xfer(struct i2c_adapter *adap, u16 addr, unsigned
 		return -EOPNOTSUPP;
 	}
 
-	mchp_corei2c_xfer(&idev->adapter, msgs, num_msgs);
+	ret = mchp_corei2c_xfer(&idev->adapter, msgs, num_msgs);
+	if (ret < 0)
+		return ret;
+
 	if (read_write == I2C_SMBUS_WRITE || size <= I2C_SMBUS_BYTE_DATA)
 		return 0;
 
-- 
2.45.2

Hi Conor,

On Mon, Jun 30, 2025 at 04:18:17PM +0100, Conor Dooley wrote:
> From: Conor Dooley <conor.dooley@microchip.com>
> 
> Introducing support for smbus re-broke i2cdetect, causing it to detect
> devices at every i2c address, just as it did prior to being fixed in
> commit 49e1f0fd0d4cb ("i2c: microchip-core: fix "ghost" detections").
> This was caused by an oversight, where the new smbus code failed to
> check the return value of mchp_corei2c_xfer(). Check it, and propagate
> any errors.
> 
> Fixes: d6ceb40538263 ("i2c: microchip-corei2c: add smbus support")
> Signed-off-by: Conor Dooley <conor.dooley@microchip.com>

merged to i2c/i2c-host-fixes.

Thanks,
Andi