On Fri, Dec 16, 2016 at 10:20:35PM +0100, Peter Rosin wrote:
> On 2016-12-16 21:06, Russell King wrote:
> > 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.
>
> Ouch! Thanks for catching this.
>
> > Fix this.
>
> But lets fix the corner case of __i2c_transfer returning 0 instead of
> the expected 1 as well (not sure if that's even possible, but lets close
> the possibility just in case), so I'd prefer if you could fix
> pca954x_reg_write() to return 0 iff __i2c_transfer(...) returns 1
> instead, and -EREMOTEIO on other non-negative return values. Thanks!
So you want something like this instead?
diff --git a/drivers/i2c/muxes/i2c-mux-pca954x.c b/drivers/i2c/muxes/i2c-mux-pca954x.c
index 8bc3d36d2837..9c4ac26c014e 100644
--- a/drivers/i2c/muxes/i2c-mux-pca954x.c
+++ b/drivers/i2c/muxes/i2c-mux-pca954x.c
@@ -151,6 +151,9 @@ 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,
@@ -179,7 +182,7 @@ 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;
--
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