RE: [PATCH] iio: max5487: Add support for Maxim digital potentiometers

From: Peter Rosin
Date: Fri Mar 25 2016 - 06:22:51 EST

Hi again,

Cristina Moraru wrote:
> Add implementation for Maxim MAX5487, MAX5488, MAX5489
> digital potentiometers.
> Signed-off-by: Cristina Moraru <cristina.moraru09@xxxxxxxxx>
> CC: Daniel Baluta <daniel.baluta@xxxxxxxxx>

Some more comments, the mcp4531 chips have n**2 + 1 positions,
therefore .max_pos in that driver isn't the number of wiper positions, it's
the actual maximum value. So, in this driver, the corrent number for
.max_pos would be 255, otherwise the reported scale is wrong (and then
you also need to adjust the EINVAL check in max5487_write_raw to use >
instead of >=).

Further comparison with the mcp4531 driver reveals that this driver does
not support IIO_CHAN_INFO_RAW in max5487_read_raw. I assume the SPI
interface does not support reading back the current value?