| Message ID | 20161216210843.26853-1-vivien.didelot@savoirfairelinux.com |
|---|---|
| State | Superseded |
| Headers | show |
On 2016-12-16 22:08, Vivien Didelot wrote: > The current code is selecting the mux channel before each operation and > does not benefit from the cached value (data->last_chan). > > That is because pca954x_select_chan() considers any non-zero values from > pca954x_reg_write() as an error. But this function (via __i2c_transfer) > returns either a negative error code or the positive number of messages > executed. > > Only check "ret" against negative values to restore the caching. > > Fixes: 463e8f845cbf ("i2c: mux: pca954x: retry updating the mux selection on failure") > Signed-off-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com> Hi Vivien, Thanks for the report, and sorry for breaking things. However, your patch got beaten by an hour by Russel King who sent approximately the same patch. I had already responded to his message when I saw yours, so I did not Cc you. Cheers, peda -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/i2c/muxes/i2c-mux-pca954x.c b/drivers/i2c/muxes/i2c-mux-pca954x.c index 8bc3d36..0469f1e 100644 --- a/drivers/i2c/muxes/i2c-mux-pca954x.c +++ b/drivers/i2c/muxes/i2c-mux-pca954x.c @@ -179,7 +179,7 @@ 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;
The current code is selecting the mux channel before each operation and does not benefit from the cached value (data->last_chan). That is because pca954x_select_chan() considers any non-zero values from pca954x_reg_write() as an error. But this function (via __i2c_transfer) returns either a negative error code or the positive number of messages executed. Only check "ret" against negative values to restore the caching. Fixes: 463e8f845cbf ("i2c: mux: pca954x: retry updating the mux selection on failure") Signed-off-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com> --- drivers/i2c/muxes/i2c-mux-pca954x.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)