Re: [PATCH 2/2] iio: light: vcnl4000: Add ps high definition for vcnl4040

[Mårten Lindahl]

On 12/18/23 16:19, Mårten Lindahl wrote:
> On 12/17/23 15:15, Jonathan Cameron wrote:
> > On Fri, 15 Dec 2023 13:43:05 +0100
> > Mårten Lindahl <marten.lindahl@xxxxxxxx> wrote:
> >
> > > The vcnl4040 proximity sensor defaults to 12 bit data resolution, but
> > > the chip also supports 16 bit data resolution, which is called 
> > > proximity
> > > high definition (PS_HD).
> > >
> > > Add read/write attribute for proximity resolution, and read attribute
> > > for available proximity resolution values for the vcnl4040 chip.
> > >
> > > Signed-off-by: Mårten Lindahl <marten.lindahl@xxxxxxxx>
> Hi Jonathan!
> > I'll review this on basis the usecase is clear (see reply to cover 
> > letter)
>
> I'll skip this patch (see reply to cover letter comment)
>
> Your are right about the paired register manipulation. Better to 
> read/write byte instead of word.

Hi Jonathan!

I now remember why the register is read as a word (CONF1/CONF2). It is 
addressed as one 16 bit register where CONF1 is the low 8 bit field and 
CONF2 is the high bit field. It is the same address/code for both:

Register PS_CONF1 - COMMAND CODE: 0x03_L (0x03 DATA BYTE LOW)

Register PS_CONF2 - COMMAND CODE: 0x03_H (0x03 DATA BYTE HIGH)

Where in my case (PS_CONF2->PS_HD[3] is the same as PS_CONF1[11])

Kind regards

Mårten

> Kind regards
>
> Mårten
>
> > The manipulation of the CONF1 and CONF2 registers in a pair is rather 
> > odd given you
> > only want to change one bit here.
> >
> > Why is that done?
> > > ---
> > >   drivers/iio/light/vcnl4000.c | 87 
> > > +++++++++++++++++++++++++++++++++++++++++++-
> > >   1 file changed, 85 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/iio/light/vcnl4000.c 
> > > b/drivers/iio/light/vcnl4000.c
> > > index fdf763a04b0b..2addff635b79 100644
> > > --- a/drivers/iio/light/vcnl4000.c
> > > +++ b/drivers/iio/light/vcnl4000.c
> > > @@ -90,6 +90,7 @@
> > >   #define VCNL4040_PS_CONF1_PS_SHUTDOWN    BIT(0)
> > >   #define VCNL4040_PS_CONF2_PS_IT    GENMASK(3, 1) /* Proximity 
> > > integration time */
> > >   #define VCNL4040_CONF1_PS_PERS    GENMASK(5, 4) /* Proximity 
> > > interrupt persistence setting */
> > > +#define VCNL4040_PS_CONF2_PS_HD        BIT(11)    /* Proximity high 
> > > definition */
> > >   #define VCNL4040_PS_CONF2_PS_INT    GENMASK(9, 8) /* Proximity 
> > > interrupt mode */
> > >   #define VCNL4040_PS_CONF3_MPS        GENMASK(6, 5) /* Proximity 
> > > multi pulse number */
> > >   #define VCNL4040_PS_MS_LED_I        GENMASK(10, 8) /* Proximity 
> > > current */
> > > @@ -170,6 +171,11 @@ static const int vcnl4040_ps_calibbias_ua[][2] = {
> > >       {0, 200000},
> > >   };
> > >   +static const int vcnl4040_ps_resolutions[2] = {
> > > +    12,
> > > +    16
> > > +};
> > > +
> > >   static const int vcnl4040_als_persistence[] = {1, 2, 4, 8};
> > >   static const int vcnl4040_ps_persistence[] = {1, 2, 3, 4};
> > >   static const int vcnl4040_ps_oversampling_ratio[] = {1, 2, 4, 8};
> > > @@ -880,6 +886,54 @@ static ssize_t 
> > > vcnl4040_write_ps_calibbias(struct vcnl4000_data *data, int val)
> > >       return ret;
> > >   }
> > >   +static ssize_t vcnl4040_read_ps_resolution(struct vcnl4000_data 
> > > *data, int *val, int *val2)
> > > +{
> > > +    int ret;
> > > +
> > > +    ret = i2c_smbus_read_word_data(data->client, VCNL4200_PS_CONF1);
> > The field seems to be in PS_CONF2.  So you are reading a word and I 
> > guess that
> > gets you two registers.  Can we not do a byte read to get just CONF2?
> > > +    if (ret < 0)
> > > +        return ret;
> > > +
> > > +    ret = FIELD_GET(VCNL4040_PS_CONF2_PS_HD, ret);
> > > +    if (ret >= ARRAY_SIZE(vcnl4040_ps_resolutions))
> > > +        return -EINVAL;
> > > +
> > > +    *val = vcnl4040_ps_resolutions[ret];
> > > +    *val2 = 0;
> > > +
> > > +    return ret;
> > > +}
> > > +
> > > +static ssize_t vcnl4040_write_ps_resolution(struct vcnl4000_data 
> > > *data, int val)
> > > +{
> > > +    unsigned int i;
> > > +    int ret;
> > > +    u16 regval;
> > > +
> > > +    for (i = 0; i < ARRAY_SIZE(vcnl4040_ps_resolutions); i++) {
> > > +        if (val == vcnl4040_ps_resolutions[i])
> > > +            break;
> > > +    }
> > > +
> > > +    if (i >= ARRAY_SIZE(vcnl4040_ps_resolutions))
> > > +        return -EINVAL;
> > > +
> > > +    mutex_lock(&data->vcnl4000_lock);
> > > +
> > > +    ret = i2c_smbus_read_word_data(data->client, VCNL4200_PS_CONF1);
> > > +    if (ret < 0)
> > > +        goto out_unlock;
> > > +
> > > +    regval = (ret & ~VCNL4040_PS_CONF2_PS_HD);
> > > +    regval |= FIELD_PREP(VCNL4040_PS_CONF2_PS_HD, i);
> > > +    ret = i2c_smbus_write_word_data(data->client, VCNL4200_PS_CONF1,
> > > +                    regval);
> > > +
> > > +out_unlock:
> > > +    mutex_unlock(&data->vcnl4000_lock);
> > > +    return ret;
> > > +}
> > c),