Re: [PATCH] iio: sx9310: Support ACPI property

[Gwendal Grignou <gwendal@chromium.org>]

On Tue, Feb 2, 2021 at 11:17 AM Stephen Boyd <swboyd@chromium.org> wrote:
>
> Quoting Gwendal Grignou (2021-02-01 22:45:41)
> > Use device_property_read_... to support both device tree and ACPI
> > bindings.
> >
> > Add support for variable array per documentation
> > ("iio/proximity/semtech,sx9310.yaml").
> >
> > Signed-off-by: Gwendal Grignou <gwendal@chromium.org>
> > ---
> >  drivers/iio/proximity/sx9310.c | 36 ++++++++++++++++++++--------------
> >  1 file changed, 21 insertions(+), 15 deletions(-)
> >
> > diff --git a/drivers/iio/proximity/sx9310.c b/drivers/iio/proximity/sx9310.c
> > index 37fd0b65a0140..1a8a441c9774d 100644
> > --- a/drivers/iio/proximity/sx9310.c
> > +++ b/drivers/iio/proximity/sx9310.c
> > @@ -1213,31 +1214,36 @@ static int sx9310_init_compensation(struct iio_dev *indio_dev)
> >  }
> >
> >  static const struct sx9310_reg_default *
> > -sx9310_get_default_reg(struct sx9310_data *data, int i,
> > +sx9310_get_default_reg(struct device *dev, int i,
> >                        struct sx9310_reg_default *reg_def)
> >  {
> > -       int ret;
> > -       const struct device_node *np = data->client->dev.of_node;
> > +       int ret, count;
> >         u32 combined[SX9310_NUM_CHANNELS] = { 4, 4, 4, 4 };
> >         unsigned long comb_mask = 0;
> >         const char *res;
> >         u32 start = 0, raw = 0, pos = 0;
> >
> >         memcpy(reg_def, &sx9310_default_regs[i], sizeof(*reg_def));
> > -       if (!np)
> > -               return reg_def;
> > -
> >         switch (reg_def->reg) {
> >         case SX9310_REG_PROX_CTRL2:
> > -               if (of_property_read_bool(np, "semtech,cs0-ground")) {
> > +               if (device_property_read_bool(dev, "semtech,cs0-ground")) {
> >                         reg_def->def &= ~SX9310_REG_PROX_CTRL2_SHIELDEN_MASK;
> >                         reg_def->def |= SX9310_REG_PROX_CTRL2_SHIELDEN_GROUND;
> >                 }
> >
> >                 reg_def->def &= ~SX9310_REG_PROX_CTRL2_COMBMODE_MASK;
> > -               of_property_read_u32_array(np, "semtech,combined-sensors",
> > -                                          combined, ARRAY_SIZE(combined));
> > -               for (i = 0; i < ARRAY_SIZE(combined); i++) {
> > +               count = device_property_read_u32_array(dev,
> > +                               "semtech,combined-sensors", NULL, 0);
> > +               if (count > 0 && count <= ARRAY_SIZE(combined))
> > +                       ret = device_property_read_u32_array(dev,
> > +                                       "semtech,combined-sensors", combined,
> > +                                       count);
> > +               else
> > +                       ret = -EINVAL;
> > +               if (ret)
> > +                       count = ARRAY_SIZE(combined);
>
> I wish this could be written simpler. Unfortunately there isn't any sort
> of for_each_device_property() iterator macro like we have with
> of_property_for_each_u32(). Or device_property_read_u32_array() can be
> OK if the length of the property doesn't exceed the size of the
> 'combined' array?
device_property_read_u32_array(...,nval) calls
acpi_data_get_property(..., nval) in ACPI case.
If nval > obj->package.count, then -EOVERFLOW is returned.
Therefore count can not be to SX9310_NUM_CHANNELS, in case
combined-sensors is only 3 entries or less.

This method of asking first for the number of element and a second
time for the values is already used at different places in the kernel:
drivers/power/supply/gpio-charger.c : see init_charge_current_limit()
or  madera_get_variable_u32_array insound/soc/codecs/madera.c.

However, it could use device_property_count_u32(...), which is more
readable than device_property_count_u32(..., NULL,0).

Gwendal.


>
> > +
> > +               for (i = 0; i < count; i++) {
> >                         if (combined[i] <= SX9310_NUM_CHANNELS)
> >                                 comb_mask |= BIT(combined[i]);
> >                 }
>
> Otherwise
>
> Reviewed-by: Stephen Boyd <swboyd@chromium.org>