iio: light: ltrf216a: Return floating point values

For better precision of input light intesity, return floating point
values through sysfs instead of an integer value

Signed-off-by: Shreeya Patel <shreeya.patel@collabora.com>
Link: https://lore.kernel.org/r/20231107192005.285534-1-shreeya.patel@collabora.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

iio: Switch i2c drivers back to use .probe()

After commit b8a1a4cd5a98 ("i2c: Provide a temporary .probe_new()
call-back type"), all drivers being converted to .probe_new() and then
03c835f498b5 ("i2c: Switch .probe() to not take an id parameter") convert
back to (the new) .probe() to be able to eventually drop .probe_new() from
struct i2c_driver.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Link: https://lore.kernel.org/r/20230515205048.19561-1-u.kleine-koenig@pengutronix.de
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

iio: light: ltrf216a: Add raw attribute

Add IIO_CHAN_INFO_RAW to the mask to be able to read raw values
from the light sensor.

The userspace code for brightness control in steam deck uses the
in_illuminance_input value through sysfs and multiplies it
with a constant stored in BIOS at factory calibration time.

The downstream driver for LTRF216A that we have been using
has incorrect formula for LUX calculation which we corrected
in the upstreamed driver.

Now to be able to use the upstreamed driver, we need to add some
magic in userspace so that the brightness control works like before
even with the updated LUX formula.

Hence, we need the raw data to calculate a constant that can be
added in userspace code.

Downstream driver LUX formula :-
(greendata*8*LTRF216A_WIN_FAC) / (data->als_gain_fac*data->int_time_fac*10)

Upstreamed driver LUX formula :-
(greendata*45*LTRF216A_WIN_FAC) / (data->als_gain_fac*data->int_time_fac)

greendata is the ALS_DATA which we would like to get through sysfs using
the raw attribute.

Signed-off-by: Shreeya Patel <shreeya.patel@collabora.com>
Link: https://lore.kernel.org/r/20220812100424.529425-1-shreeya.patel@collabora.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

iio: light: Add support for ltrf216a sensor

Add initial support for ltrf216a ambient light sensor.

Datasheet: https://gitlab.collabora.com/shreeya/iio/-/blob/master/LTRF216A.pdf
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Co-developed-by: Zhigang Shi <Zhigang.Shi@liteon.com>
Signed-off-by: Zhigang Shi <Zhigang.Shi@liteon.com>
Co-developed-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Signed-off-by: Shreeya Patel <shreeya.patel@collabora.com>
Link: https://lore.kernel.org/r/20220725104050.491396-3-shreeya.patel@collabora.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>