i2c: mux: pca954x: 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 pca954x_reg_write() return a negative error code for
all failure cases.

Fixes: 463e8f845cbf ("i2c: mux: pca954x: retry updating the mux selection on failure")
Acked-by: Peter Rosin <peda@axentia.se>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

diff --git a/drivers/i2c/muxes/i2c-mux-pca954x.c b/drivers/i2c/muxes/i2c-mux-pca954x.c
index 9a348ee4dc14deb9eb1686fd1a20dc672b73a5df..dd18b9ccb1f40b4f6ddf5904e1f6d529931801df 100644 (file)
--- a/drivers/i2c/muxes/i2c-mux-pca954x.c
+++ b/drivers/i2c/muxes/i2c-mux-pca954x.c
@@ -167,6 +167,9 @@ static int pca954x_reg_write(struct i2c_adapter *adap,
                buf[0] = val;
                msg.buf = buf;
                ret = __i2c_transfer(adap, &msg, 1);
+
+               if (ret >= 0 && ret != 1)
+                       ret = -EREMOTEIO;
        } else {
                union i2c_smbus_data data;
                ret = adap->algo->smbus_xfer(adap, client->addr,
@@ -195,7 +198,7 @@ static int pca954x_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) {
                ret = pca954x_reg_write(muxc->parent, client, regval);
-               data->last_chan = ret ? 0 : regval;
+               data->last_chan = ret < 0 ? 0 : regval;
        }
 
        return ret;