Re: [PATCH v2 2/7] gpio: regmap: Add configurable dir/value order

[Sander Vanheule]

Hi Michael,

On Tue, 2021-05-18 at 10:39 +0200, Michael Walle wrote:
> Hi,
> 
> Am 2021-05-17 21:28, schrieb Sander Vanheule:
> > GPIO chips may not support setting the output value when a pin is
> > configured as an input, although the current implementation assumes 
> > this
> > is always possible.
> > 
> > Add support for setting pin direction before value. The order defaults
> > to setting the value first, but this can be reversed by setting the
> > regmap_config.no_set_on_input flag, similar to the corresponding flag 
> > in
> > the gpio-mmio driver.
> > 
> > Signed-off-by: Sander Vanheule <sander@xxxxxxxxxxxxx>
> > ---
> >  drivers/gpio/gpio-regmap.c  | 20 +++++++++++++++++---
> >  include/linux/gpio/regmap.h |  3 +++
> >  2 files changed, 20 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/gpio/gpio-regmap.c b/drivers/gpio/gpio-regmap.c
> > index 134cedf151a7..1cdb20f8f8b4 100644
> > --- a/drivers/gpio/gpio-regmap.c
> > +++ b/drivers/gpio/gpio-regmap.c
> > @@ -170,14 +170,25 @@ static int gpio_regmap_direction_input(struct
> > gpio_chip *chip,
> >         return gpio_regmap_set_direction(chip, offset, false);
> >  }
> > 
> > -static int gpio_regmap_direction_output(struct gpio_chip *chip,
> > -                                       unsigned int offset, int value)
> > +static int gpio_regmap_dir_out_val_first(struct gpio_chip *chip,
> > +                                        unsigned int offset, int value)
> 
> Can we leave the name as is? TBH I find these two similar names
> super confusing. Maybe its just me, though.

Sure. This is the implementation used in gpio-mmio.c to provide the same
functionality, so I had used that for consistenty between the two drivers.

> >  {
> >         gpio_regmap_set(chip, offset, value);
> > 
> >         return gpio_regmap_set_direction(chip, offset, true);
> >  }
> > 
> > +static int gpio_regmap_dir_out_dir_first(struct gpio_chip *chip,
> > +                                        unsigned int offset, int value)
> > +{
> > +       int err;
> 
> use ret for consistency here
> 
> > +
> > +       err = gpio_regmap_set_direction(chip, offset, true);
> > +       gpio_regmap_set(chip, offset, value);
> > +
> > +       return err;
> > +}
> > +
> 
> Instead of adding a new one, we can also just check no_set_on_input
> in gpio_regmap_direction_output(), which I'd prefer.
> 
> static int gpio_regmap_direction_output(struct gpio_chip *chip,
>                                         unsigned int offset, int value)
> {
>         struct gpio_regmap *gpio = gpiochip_get_data(chip);
>         int ret;
> 
>         if (gpio->no_set_on_input) {
>                 /* some smart comment here, also mention gliches */
>                 ret = gpio_regmap_set_direction(chip, offset, true);
>                 gpio_regmap_set(chip, offset, value);
>         } else {
>                 gpio_regmap_set(chip, offset, value);
>                 ret = gpio_regmap_set_direction(chip, offset, true);
>         }
> 
>         return ret;
> }
> 

This would certainly make the code a bit easier to follow when you're not
familiar with it :-)
I also see the other functions do checks on static values too, so I'll bring
this function in line with that style.


> >  void gpio_regmap_set_drvdata(struct gpio_regmap *gpio, void *data)
> >  {
> >         gpio->driver_data = data;
> > @@ -277,7 +288,10 @@ struct gpio_regmap *gpio_regmap_register(const
> > struct gpio_regmap_config *config
> >         if (gpio->reg_dir_in_base || gpio->reg_dir_out_base) {
> >                 chip->get_direction = gio_regmap_get_direction;
> >                 chip->direction_input = gpio_regmap_direction_input;
> > -               chip->direction_output = gpio_regmap_direction_output;
> > +               if (config->no_set_on_input)
> > +                       chip->direction_output =
> > gpio_regmap_dir_out_dir_first;
> > +               else
> > +                       chip->direction_output =
> > gpio_regmap_dir_out_val_first;
> >         }
> > 
> >         ret = gpiochip_add_data(chip, gpio);
> > diff --git a/include/linux/gpio/regmap.h b/include/linux/gpio/regmap.h
> > index 334dd928042b..2a732f8f23be 100644
> > --- a/include/linux/gpio/regmap.h
> > +++ b/include/linux/gpio/regmap.h
> > @@ -30,6 +30,8 @@ struct regmap;
> >   * @reg_dir_out_base:  (Optional) out setting register base address
> >   * @reg_stride:                (Optional) May be set if the registers (of
> > the
> >   *                     same type, dat, set, etc) are not consecutive.
> > + * @no_set_on_input:   Set if output value can only be set when the 
> > direction
> > + *                     is configured as output.
> 
> set_direction_first ?

This negation can indeed be a bit confusing, I'll change this. As Andy
suggested, I just went for a 'quirks' field, with currently only one defined
flag.

Best,
Sander