On 2016-12-17 00:23, Russell King - ARM Linux wrote:
> 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?
Yes, but I was originally thinking that the second hunk was no
longer needed...
Either way,
Acked-by: Peter Rosin <peda@xxxxxxxxxx>
Cheers,
peda
> 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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