linux-kernel - [PATCH v2] i2c: microchip-core: re-fix fake detections w/ i2cdetect

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Message-ID: <20250626-unusable-excess-da94ebc218e8@spud>
Date: Thu, 26 Jun 2025 17:15:39 +0100
From: Conor Dooley <conor@...nel.org>
To: linux-i2c@...r.kernel.org
Cc: conor@...nel.org,
	Conor Dooley <conor.dooley@...rochip.com>,
	Daire McNamara <daire.mcnamara@...rochip.com>,
	Andi Shyti <andi.shyti@...nel.org>,
	linux-kernel@...r.kernel.org
Subject: [PATCH v2] i2c: microchip-core: re-fix fake detections w/ i2cdetect

From: Conor Dooley <conor.dooley@...rochip.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@...rochip.com>
---
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@...rochip.com>
CC: Daire McNamara <daire.mcnamara@...rochip.com>
CC: Andi Shyti <andi.shyti@...nel.org>
CC: linux-i2c@...r.kernel.org
CC: linux-kernel@...r.kernel.org
---
 drivers/i2c/busses/i2c-microchip-corei2c.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/i2c/busses/i2c-microchip-corei2c.c b/drivers/i2c/busses/i2c-microchip-corei2c.c
index 492bf4c34722c..7505bce3a06cd 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;
@@ -506,6 +507,9 @@ static int mchp_corei2c_smbus_xfer(struct i2c_adapter *adap, u16 addr, unsigned
 	}
 
 	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