i2c: mux: mlxcpld: fix i2c mux selection caching

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 test 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@axentia.se>
Acked-by: Vadim Pasternak <vadimp@mellanox.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

diff --git a/drivers/i2c/muxes/i2c-mux-mlxcpld.c b/drivers/i2c/muxes/i2c-mux-mlxcpld.c
index 3ab654bbfab56f4fe299800e2372fbee86b1385d..b7ca249ec9c38b884ed48fbb8387dcc6729f1cc6 100644 (file)
--- 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;