linux-kernel - [PATCH] HID: mcp2221: cancel last I2C command on read error

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Message-ID: <20260206163258.130584-1-romain.sioen@microchip.com>
Date: Fri, 6 Feb 2026 17:32:58 +0100
From: Romain Sioen <romain.sioen@...rochip.com>
To: <linux-kernel@...r.kernel.org>
CC: <gupt21@...il.com>, <jikos@...nel.org>, Romain Sioen
	<romain.sioen@...rochip.com>
Subject: [PATCH] HID: mcp2221: cancel last I2C command on read error

When an I2C SMBus read operation fails, the MCP2221 internal state machine
may not reset correctly, causing subsequent transactions to fail.

By adding a short delay and explicitly cancelling the last command,
we ensure the device is ready for the next operation.

Fix an issue where i2cdetect was not able to detect all devices correctly
on the bus.

Signed-off-by: Romain Sioen <romain.sioen@...rochip.com>
---
 drivers/hid/hid-mcp2221.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/hid/hid-mcp2221.c b/drivers/hid/hid-mcp2221.c
index 64dcedbcc0fc9..5eefdcc477b9d 100644
--- a/drivers/hid/hid-mcp2221.c
+++ b/drivers/hid/hid-mcp2221.c
@@ -353,6 +353,8 @@ static int mcp_i2c_smbus_read(struct mcp2221 *mcp,
 				usleep_range(90, 100);
 				retries++;
 			} else {
+				usleep_range(980, 1000);
+				mcp_cancel_last_cmd(mcp);
 				return ret;
 			}
 		} else {
-- 
2.53.0