| From: Russell King <rmk+kernel@armlinux.org.uk> |
| Date: Sat, 17 Dec 2016 12:10:56 +0000 |
| Subject: i2c: mux: pca954x: fix i2c mux selection caching |
| |
| 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 <peda@axentia.se> |
| Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk> |
| Signed-off-by: Wolfram Sang <wsa@the-dreams.de> |
| [bwh: Backported to 3.16: adjust context] |
| Signed-off-by: Ben Hutchings <ben@decadent.org.uk> |
| --- |
| 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; |
