[PATCH 5.15 185/570] iio: potentiometer: mcp4131: fix double application of wiper shift

Greg Kroah-Hartman
2026-04-13T16:26:03Z

From: Lukas Schmid <lukas.schmid@netcube.li>

commit 85e4614524dca6c0a43874f475a17de2b9725648 upstream.

The MCP4131 wiper address is shifted twice when preparing the SPI
command in mcp4131_write_raw().

The address is already shifted when assigned to the local variable
"address", but is then shifted again when written to data->buf[0].
This results in an incorrect command being sent to the device and
breaks wiper writes to the second channel.

Remove the second shift and use the pre-shifted address directly
when composing the SPI transfer.

Fixes: 22d199a53910 ("iio: potentiometer: add driver for Microchip MCP413X/414X/415X/416X/423X/424X/425X/426X")
Signed-off-by: Lukas Schmid <lukas.schmid@netcube.li>#
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/iio/potentiometer/mcp4131.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/iio/potentiometer/mcp4131.c
+++ b/drivers/iio/potentiometer/mcp4131.c
@@ -222,7 +222,7 @@ static int mcp4131_write_raw(struct iio_

mutex_lock(&data->lock);

- data->buf[0] = address << MCP4131_WIPER_SHIFT;
+ data->buf[0] = address;
data->buf[0] |= MCP4131_WRITE | (val >> 8);
data->buf[1] = val & 0xFF; /* 8 bits here */