RE: [PATCH v3 2/2] iio: dac: ad5706r: Add support for AD5706R DAC

[Torreno, Alexis Czezar]

> > > > Changes since v1:
> > > >   - Removed PWM, GPIO, clock generator, debugfs, regmap,
> > > > IIO_BUFFER
> > >
> > > Why was regmap removed?! Was it not used?
> >
> > As far as I understand it, regmap also gives access to debugfs. When I
> > removed debugfs I also added regmap as removed.
> 
> Not only debugfs, and it's unrelated to the any custom debugfs interfaces in
> the driver, it's just a feature out-of-the-box of regmap.
> 
> > For the spi write/read I am not using regmap as the device has some
> > features that I think regmap_read/write couldn't support. Namely the
> > variable data width, as the device only accepts exact amount of clock
> > cycles. Future patches will also add variable SPI speed.
> 
> We have a lot of flexibility in regmap core. Do you think it can be improved /
> extended to cover the cases like yours?
> 

To neatly summarize, my needs are: (in future patches)
1. SPI read/write can have different frequencies and runtime changeable
2. SPI data bits needs to be exactly 8bits or 16bits depending on register width
3. DAC Device reads SPI command bits [14:12] for communication, not just chip select

For regmap to be used
1. regmap_config would need new read_speed and write_speed entries.
2. val_bits must now be changeable depending on the need.
3. I think the read/write_flag_mask can do this.

1) is relatively easy I think, but am not sure with 2) as it might break other regmap core code
that already assumes it to be fixed.
Feels like a lot of work for a niche amount of devices, I may still lean on the opinion of
keeping regmap as is.

Regards,
Alexis