Re: [PATCH v2 11/11] iio: dac: support the ad9739a RF DAC

[Jonathan Cameron <jic23@kernel.org>]

On Fri, 5 Apr 2024 17:00:09 +0200
Nuno Sa <nuno.sa@analog.com> wrote:

> The AD9739A is a 14-bit, 2.5 GSPS high performance RF DACs that are capable
> of synthesizing wideband signals from DC up to 3 GHz.
> 
> A dual-port, source synchronous, LVDS interface simplifies the digital
> interface with existing FGPA/ASIC technology. On-chip controllers are used
> to manage external and internal clock domain variations over temperature to
> ensure reliable data transfer from the host to the DAC core.
> 
> Co-developed-by: Dragos Bogdan <dragos.bogdan@analog.com>
> Signed-off-by: Dragos Bogdan <dragos.bogdan@analog.com>
> Signed-off-by: Nuno Sa <nuno.sa@analog.com>

The only thing I really have remaining questions on is the choice
of chan_spec with altvoltage and voltage channels.  Why does that
split make sense?  It's odd enough that some comments in the code would
be a good thing to add.

Jonathan

> new file mode 100644
> index 000000000000..9b91d66f826c
> --- /dev/null
> +++ b/drivers/iio/dac/ad9739a.c
> @@ -0,0 +1,454 @@

> +
> +static struct iio_chan_spec ad9739a_channels[] = {
> +	{
> +		.type = IIO_ALTVOLTAGE,

So this looks a little unusual. Perhaps some comments on why it
is appropriate to have this channel.

In reality there is only one channel I think?

> +		.indexed = 1,
> +		.output = 1,
> +		.scan_index = -1,
> +	},
> +	{
> +		.type = IIO_VOLTAGE,
> +		.indexed = 1,
> +		.info_mask_shared_by_all = BIT(IIO_CHAN_INFO_SAMP_FREQ),
> +		.output = 1,
> +		.ext_info = ad9739a_ext_info,
> +		.scan_type = {
> +			.sign = 's',
> +			.storagebits = 16,
> +			.realbits = 16,
> +		},
> +	}
> +};