On 8/21/24 8:16 AM, Jonathan Cameron wrote:
> On Tue, 20 Aug 2024 10:58:36 -0500
> David Lechner <dlechner@xxxxxxxxxxxx> wrote:
>
>> The AD4695 has a calibration feature that allows the user to compensate
>> for variations in the analog front end. This implements this feature in
>> the driver using the standard `calibgain` and `calibbias` attributes.
>>
>> Signed-off-by: David Lechner <dlechner@xxxxxxxxxxxx>
> Hi David,
>
> Whilst some of the messy value manipulation is unavoidable
> (oh for signed integer zero!), I wonder if we can at least
> move one case into the core.
>
> See below.
>
>> +
>> +static int ad4695_write_raw(struct iio_dev *indio_dev,
>> + struct iio_chan_spec const *chan,
>> + int val, int val2, long mask)
>> +{
>> + struct ad4695_state *st = iio_priv(indio_dev);
>> + unsigned int reg_val;
>> + int ret;
>> +
>> + iio_device_claim_direct_scoped(return -EBUSY, indio_dev) {
>> + switch (mask) {
>> + case IIO_CHAN_INFO_CALIBSCALE:
>> + switch (chan->type) {
>> + case IIO_VOLTAGE:
>> + if (val < 0 || val2 < 0)
>> + reg_val = 0;
>> + else if (val > 1)
>> + reg_val = U16_MAX;
>> + else
>> + reg_val = (val * (1 << 16) +
>> + mul_u64_u32_div(val2, 1 << 16,
>> + MICRO)) / 2;
> Maybe worth extending iio_write_channel_info() to handle
> IIO_VAL_FRACTIONAL_LOG2()?
> It'll look much like this and you'll need to provide write_raw_get_fmt()
> so the core know what to do with the value formatting.
>
> I don't really like the mixture here between the read path being able
> to rely on the core code to deal with the /2^X and the write path not.
Sounds like a good idea to me.
It seems like we would need to add an extra out parameter to
write_raw_get_fmt to say what we want the X in 2^X to be. For
example, we would want to make sure the val2 we get in write_raw
for this driver is 15.
>> +
>> + return regmap_write(st->regmap16,
>> + AD4695_REG_GAIN_IN(chan->scan_index),
>> + reg_val);
>> + default:
>> + return -EINVAL;
>
>
>
