smbus functions return -ve on error, 0 on success. However,
__i2c_transfer() have a different return signature - -ve on error, or
number of buffers transferred (which may be zero or greater.)
The upshot of this is that the sense of the text is reversed when using
the mux on a bus supporting the master_xfer method: we cache the value
and never retry if we fail to transfer any buffers, but if we succeed,
we clear the cached value
Fix this by making mlxcpld_mux_reg_write() return a -ve error code for
all failure cases, just as was done in commit 7f638c1cb0a1 ("i2c: mux:
pca954x: fix i2c mux selection caching")
This also aligns the implementations of these two muxes in this area.
Signed-off-by: Peter Rosin <peda@xxxxxxxxxx>
---
Hi!
I audited the other i2c muxes for similar problems after the recent regression
report for the pca954x driver [1], and found only this.
I obviously don't have the hardware to test this patch.
Anyway, this driver is probably lower profile than the pca954x, but this
still needs fixing in my opinion...
Cheers,
peda
[1] http://www.spinics.net/lists/linux-i2c/msg27586.html
drivers/i2c/muxes/i2c-mux-mlxcpld.c | 24 +++++++++++++-----------
1 file changed, 13 insertions(+), 11 deletions(-)
diff --git a/drivers/i2c/muxes/i2c-mux-mlxcpld.c b/drivers/i2c/muxes/i2c-mux-mlxcpld.c
index 3ab654bbfab5..b7ca249ec9c3 100644
--- a/drivers/i2c/muxes/i2c-mux-mlxcpld.c
+++ b/drivers/i2c/muxes/i2c-mux-mlxcpld.c
@@ -95,6 +95,7 @@ static int mlxcpld_mux_reg_write(struct i2c_adapter *adap,
struct i2c_client *client, u8 val)
{
struct mlxcpld_mux_plat_data *pdata = dev_get_platdata(&client->dev);
+ int ret = -ENODEV;
if (adap->algo->master_xfer) {
struct i2c_msg msg;
@@ -104,17 +105,21 @@ static int mlxcpld_mux_reg_write(struct i2c_adapter *adap,
msg.flags = 0;
msg.len = 2;
msg.buf = msgbuf;
- return __i2c_transfer(adap, &msg, 1);
+ ret = __i2c_transfer(adap, &msg, 1);
+
+ if (ret >= 0 && ret != 1)
+ ret = -EREMOTEIO;
} else if (adap->algo->smbus_xfer) {
union i2c_smbus_data data;
data.byte = val;
- return adap->algo->smbus_xfer(adap, client->addr,
- client->flags, I2C_SMBUS_WRITE,
- pdata->sel_reg_addr,
- I2C_SMBUS_BYTE_DATA, &data);
- } else
- return -ENODEV;
+ ret = adap->algo->smbus_xfer(adap, client->addr,
+ client->flags, I2C_SMBUS_WRITE,
+ pdata->sel_reg_addr,
+ I2C_SMBUS_BYTE_DATA, &data);
+ }
+
+ return ret;
}
static int mlxcpld_mux_select_chan(struct i2c_mux_core *muxc, u32 chan)
@@ -127,10 +132,7 @@ static int mlxcpld_mux_select_chan(struct i2c_mux_core *muxc, u32 chan)
/* Only select the channel if its different from the last channel */
if (data->last_chan != regval) {
err = mlxcpld_mux_reg_write(muxc->parent, client, regval);
- if (err)
- data->last_chan = 0;
- else
- data->last_chan = regval;
+ data->last_chan = err < 0 ? 0 : regval;
}
return err;
--
2.1.4
--
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