linux-kernel - Re: [PATCH 3/5] mfd: axp20x: Add support for the AXP808 PMIC

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Date:   Fri, 3 Feb 2017 22:47:54 +0100
From:   Rask Ingemann Lambertsen <rask@...melder.dk>
To:     Chen-Yu Tsai <wens@...e.org>
Cc:     Mark Rutland <mark.rutland@....com>,
        devicetree <devicetree@...r.kernel.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Mark Brown <broonie@...nel.org>,
        Lee Jones <lee.jones@...aro.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        Maxime Ripard <maxime.ripard@...e-electrons.com>
Subject: Re: [PATCH 3/5] mfd: axp20x: Add support for the AXP808 PMIC

On Thu, Feb 02, 2017 at 03:23:33PM +0800, Chen-Yu Tsai wrote:
> On Fri, Jan 27, 2017 at 5:25 AM, Rask Ingemann Lambertsen
> <rask@...melder.dk> wrote:
[...]
> > diff --git a/drivers/mfd/axp20x.c b/drivers/mfd/axp20x.c
> > index 25115fe..2d3383e 100644
> > --- a/drivers/mfd/axp20x.c
> > +++ b/drivers/mfd/axp20x.c
[...]
> > @@ -148,6 +149,13 @@ static const struct regmap_range axp806_writeable_ranges[] = {
> >         regmap_reg_range(AXP806_REG_ADDR_EXT, AXP806_REG_ADDR_EXT),
> >  };
> >
> > +static const struct regmap_range axp808_writeable_ranges[] = {
> > +       regmap_reg_range(AXP20X_DATACACHE(0), AXP20X_DATACACHE(3)),
> > +       regmap_reg_range(AXP806_PWR_OUT_CTRL1, AXP806_CLDO3_V_CTRL),
> > +       regmap_reg_range(AXP20X_IRQ1_EN, AXP20X_IRQ2_EN),
> > +       regmap_reg_range(AXP20X_IRQ1_STATE, AXP20X_IRQ2_STATE),
> > +};
> > +
> >  static const struct regmap_range axp806_volatile_ranges[] = {
> >         regmap_reg_range(AXP20X_IRQ1_STATE, AXP20X_IRQ2_STATE),
> >  };
> > @@ -162,6 +170,11 @@ static const struct regmap_access_table axp806_volatile_table = {
> >         .n_yes_ranges   = ARRAY_SIZE(axp806_volatile_ranges),
> >  };
> >
> > +static const struct regmap_access_table axp808_writeable_table = {
> > +       .yes_ranges     = axp808_writeable_ranges,
> > +       .n_yes_ranges   = ARRAY_SIZE(axp808_writeable_ranges),
> 
> You could probably get away with using axp806_writeable_ranges,
> and pass ARRAY_SIZE(axp808_writeable_ranges) - 1 for .n_yes_ranges.

Assuming that register ranges not supported on the AXP808 are always
at one end of the table, I think it will ease maintenance by avoiding
duplicate data should entries be added or removed in the future. I'll put
a comment above axp806_writeable_ranges to point out what's going on.

> Or maybe the compiler figures out the 2 arrays share common data.

It doesn't as of gcc 6.2.1.

-- 
Rask Ingemann Lambertsen