Re: [PATCH 1/2] gpio: regmap: Support few IC specific operations

[Michael Walle]

Am 2021-05-20 14:42, schrieb Vaittinen, Matti:
> On Thu, 2021-05-20 at 14:22 +0200, Michael Walle wrote:
> > Am 2021-05-20 14:00, schrieb Matti Vaittinen:
> > > On Thu, 2021-05-20 at 13:42 +0200, Michael Walle wrote:
> > > > Am 2021-05-20 13:28, schrieb Matti Vaittinen:
> > > > > The set_config and init_valid_mask GPIO operations are usually
> > > > > very
> > > > > IC
> > > > > specific. Allow IC drivers to provide these custom operations
> > > > > at
> > > > > gpio-regmap registration.
> > > > >
> > > > > Signed-off-by: Matti Vaittinen <
> > > > > matti.vaittinen@xxxxxxxxxxxxxxxxx>
> > > > > ---
> > > > >  drivers/gpio/gpio-regmap.c  | 49
> > > > > +++++++++++++++++++++++++++++++++++++
> > > > >  include/linux/gpio/regmap.h | 13 ++++++++++
> > > > >  2 files changed, 62 insertions(+)
> > > > >
> > > > > diff --git a/drivers/gpio/gpio-regmap.c b/drivers/gpio/gpio-
> > > > > regmap.c
> > > > > index 134cedf151a7..315285cacd3f 100644
> > > > > --- a/drivers/gpio/gpio-regmap.c
> > > > > +++ b/drivers/gpio/gpio-regmap.c
> > > > > @@ -27,6 +27,10 @@ struct gpio_regmap {
> > > > >  	int (*reg_mask_xlate)(struct gpio_regmap *gpio,
> > > > > unsigned int
> > > > > base,
> > > > >  			      unsigned int offset, unsigned int
> > > > > *reg,
> > > > >  			      unsigned int *mask);
> > > > > +	int (*set_config)(struct regmap *regmap, void *drvdata,
> > > > > +			  unsigned int offset, unsigned long
> > > > > config);
> > > > > +	int (*init_valid_mask)(struct regmap *regmap, void
> > > > > *drvdata,
> > > > > +				unsigned long *valid_mask,
> > > > > unsigned int
> > > > > ngpios);
> > > >
> > > > Maybe we should also make the first argument a "struct
> > > > gpio_regmap"
> > > > and provide a new gpio_regmap_get_regmap(struct gpio_regmap).
> > > > Thus
> > > > having a similar api as for the reg_mask_xlate(). Andy?
> > >
> > > I don't really see the reason of making this any more complicated
> > > for
> > > IC drivers. If we don't open the struct gpio_regmap to IC drivers -
> > > then they never need the struct gpio_regmap pointer itself but each
> > > IC
> > > driver would need to do some unnecessary function call
> > > (gpio_regmap_get_regmap() in this case). I'd say that would be
> > > unnecessary bloat.
> >
> > If there is ever the need of additional parameters, you'll have to
> > modify that parameter list. Otherwise you'll just have to add a new
> > function. Thus might be more future proof.
>
> I do hope the "void *drvdata" allows enough flexibility so that there
> is no need to add new parameters.

Thats for information passed from the user of gpio_regmap to the
callbacks.

> And if there is, then I don't see how
> the struct gpio_regmap pointer would have saved us - unless we open the
> contents of struct gpio_regmap to IC drivers. (Which might make sense
> because that already contains plenty of register details which may need
> to be duplicated to drvdata for some IC-specific callbacks. Here we
> again have analogy to regulator_desc - which I have often used also in
> IC-specific custom callbacks. But as long as we hope to keep the struct
> gpio_regmap private I would not add it in arguments).

Because that (opaque) argument is then used for the helper functions
of gpio_regmap.

-michael