On 02/13/2013 11:02 AM, Doug Anderson wrote:
> The force_nr parameter to i2c_add_mux_adapter() uses 0 to signify that
> we don't want to force the bus number of the adapter. This is
> non-ideal because:
> * 0 is actually a valid bus number to request
> * i2c_add_numbered_adapter() (which i2c_add_mux_adapter() calls) uses
> -1 to mean the same thing. That means extra logic in
> i2c_add_mux_adapter().
>
> Fix i2c_add_mux_adapter() to use -1 and update all mux drivers
> accordingly.
>
> Signed-off-by: Doug Anderson <dianders@xxxxxxxxxxxx>
> ---
> Notes:
> - If there's a good reason that force_nr uses 0 for auto then feel
> free to drop this patch. I've place it at the end of the series to
> make it easy to just drop it.
IIRC (and I only vaguely do...) it's because:
> diff --git a/drivers/i2c/muxes/i2c-mux-gpio.c b/drivers/i2c/muxes/i2c-mux-gpio.c
> index 9f50ef0..301ed0b 100644
> --- a/drivers/i2c/muxes/i2c-mux-gpio.c
> +++ b/drivers/i2c/muxes/i2c-mux-gpio.c
> @@ -208,7 +208,7 @@ static int i2c_mux_gpio_probe(struct platform_device *pdev)
> }
>
> for (i = 0; i < mux->data.n_values; i++) {
> - u32 nr = mux->data.base_nr ? (mux->data.base_nr + i) : 0;
> + int nr = mux->data.base_nr ? (mux->data.base_nr + i) : -1;
Here, mux->data.base_nr is platform data (or copied directly from it),
and any field in a platform data struct stored in a global variable not
explicitly initialized would be 0, hence 0 would typically mean "no
explicit bus number desired". Since a mux can't exist without a parent
I2C bus, it's unlikely anyone would want a mux to be I2C bus 0, but
rather the parent to have that number.
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