3.16.42-rc1 review patch. If anyone has any objections, please let me know.
------------------ From: Russell King <[email protected]> commit 7f638c1cb0a1112dbe0b682a42db30521646686b upstream. 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 <[email protected]> Signed-off-by: Russell King <[email protected]> Signed-off-by: Wolfram Sang <[email protected]> [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings <[email protected]> --- drivers/i2c/muxes/i2c-mux-pca954x.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) --- a/drivers/i2c/muxes/i2c-mux-pca954x.c +++ b/drivers/i2c/muxes/i2c-mux-pca954x.c @@ -133,6 +133,9 @@ static int pca954x_reg_write(struct i2c_ buf[0] = val; msg.buf = buf; ret = adap->algo->master_xfer(adap, &msg, 1); + + if (ret >= 0 && ret != 1) + ret = -EREMOTEIO; } else { union i2c_smbus_data data; ret = adap->algo->smbus_xfer(adap, client->addr, @@ -161,7 +164,7 @@ static int pca954x_select_chan(struct i2 /* Only select the channel if its different from the last channel */ if (data->last_chan != regval) { ret = pca954x_reg_write(adap, client, regval); - data->last_chan = ret ? 0 : regval; + data->last_chan = ret < 0 ? 0 : regval; } return ret;
