Re: [PATCH 10/20] gpio: pca953x: Add optional reset gpio control

[Steve Longerbeam]

Hi Linus, Lothar,


On 12/30/2016 05:17 AM, Linus Walleij wrote:
> On Thu, Dec 29, 2016 at 11:27 PM, Steve Longerbeam
> <slongerbeam@xxxxxxxxx> wrote:
>
> > Add optional reset-gpios pin control. If present, de-assert the
> > specified reset gpio pin to bring the chip out of reset.
> >
> > Signed-off-by: Steve Longerbeam <steve_longerbeam@xxxxxxxxxx>
> > Cc: Linus Walleij <linus.walleij@xxxxxxxxxx>
> > Cc: Alexandre Courbot <gnurou@xxxxxxxxx>
> > Cc: linux-gpio@xxxxxxxxxxxxxxx
> > Cc: linux-kernel@xxxxxxxxxxxxxxx
> This seems like a separate patch from the other 19 patches so please send it
> separately so I can handle logistics easier in the future.

Ok, I'll send the next version separately.

> > @@ -133,6 +134,7 @@ struct pca953x_chip {
> >          const char *const *names;
> >          unsigned long driver_data;
> >          struct regulator *regulator;
> > +       struct gpio_desc *reset_gpio;
> Why do you even keep this around in the device state container?
>
> As you only use it in the probe() function, use a local variable.
>
> The descriptor will be free():ed by the devm infrastructure anyways.

I think my reasoning for putting the gpio handle into the device
struct was for possibly using it for run-time reset control at some
point. But that could be done later if needed, so I'll go ahead and
make it local.

> > +               /* see if we need to de-assert a reset pin */
> > +               chip->reset_gpio = devm_gpiod_get_optional(&client->dev,
> > +                                                          "reset",
> > +                                                          GPIOD_OUT_LOW);
> > +               if (IS_ERR(chip->reset_gpio)) {
> > +                       dev_err(&client->dev, "request for reset pin failed\n");
> > +                       return PTR_ERR(chip->reset_gpio);
> > +               }
> Nice.
>
> > +               if (chip->reset_gpio) {
> > +                       /* bring chip out of reset */
> > +                       dev_info(&client->dev, "releasing reset\n");
> > +                       gpiod_set_value(chip->reset_gpio, 0);
> > +               }
> Is this really needed given that you set it low in the
> devm_gpiod_get_optional()?

Yep, this is left over from a previous iteration, but it isn't needed now.
I'll remove it.

Steve