linux-kernel - Re: [PATCH] iio: dac: DS4424: add Maxim DS4422/DS4424 DAC driver support

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Date:   Mon, 26 Jun 2017 14:56:39 -0500
From:   Rob Herring <robh@...nel.org>
To:     Ismail Kose <Ismail.Kose@...imintegrated.com>
Cc:     jic23@...nel.org, knaack.h@....de, lars@...afoo.de,
        pmeerw@...erw.net, mark.rutland@....com, vilhelm.gray@...il.com,
        linus.walleij@...aro.org, jeff.dagenais@...il.com,
        fabrice.gasnier@...com, gwenhael.goavec-merou@...bucayre.com,
        peda@...ntia.se, maxime.roussinbelanger@...il.com,
        ihkose@...il.com, linux-iio@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iio: dac: DS4424: add Maxim DS4422/DS4424 DAC driver
 support

On Fri, Jun 23, 2017 at 04:04:04PM -0700, Ismail Kose wrote:
> From: "Ismail H. Kose" <ihkose@...il.com>
> 
> Add iio driver for DS4422/DS4424 chips that support two/four channel 7-bit
> Sink/Source Current DAC.
> 
> The driver supports device tree and platfrom files for the configurations.
> 
> Datasheet publicly available at:
> https://datasheets.maximintegrated.com/en/ds/DS4422-DS4424.pdf
> 
> Signed-off-by: Ismail Kose <Ismail.Kose@...imintegrated.com>
> ---
>  .../devicetree/bindings/iio/dac/ds4424.txt         |  41 ++

Please make the binding a separate patch.

>  drivers/iio/dac/Kconfig                            |   9 +
>  drivers/iio/dac/Makefile                           |   1 +
>  drivers/iio/dac/ds4424.c                           | 733 +++++++++++++++++++++
>  include/linux/iio/dac/ds4424.h                     |  29 +
>  5 files changed, 813 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/iio/dac/ds4424.txt
>  create mode 100644 drivers/iio/dac/ds4424.c
>  create mode 100644 include/linux/iio/dac/ds4424.h
> 
> diff --git a/Documentation/devicetree/bindings/iio/dac/ds4424.txt b/Documentation/devicetree/bindings/iio/dac/ds4424.txt
> new file mode 100644
> index 000000000000..03c1b575a6db
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iio/dac/ds4424.txt
> @@ -0,0 +1,41 @@
> +Maxim Integrated DS4422/DS4424 DAC device driver

Bindings describe h/w not device drivers.

> +
> +Required properties:
> +	- compatible: Must be "maxim,ds4422" or "maxim,ds4424"
> +	- reg: Should contain the DAC I2C address
> +	- min_rfs, max_rfs: In order to get the correct processed data values,

Don't use '_' in property names, and these all need vendor prefixes.

> +		   these resistor values should be changed to the correct values
> +		   that match the user's system resistor values for RFS0 to RFS1.
> +		   Resistance values for rfs_resistor are listed in 100 Ohm units;
> +		   ie, 800 is 80K. Acceptable RFS values are 40K to 160K.

Just use ohms (adding a suffix). Perhaps do a 2 value property with min 
and max values.

> +	- ifs_scale: 61000*100 = 6100000 = 100,000,000 * .976/16
> +	- max_picoamp: Should contain DAC maximum pico amper value.

Add any new units to property-units.txt.

> +	- rfs_resistor: Should contain reference resistor

unit suffix?

> +	- iio map: Should contain IIO Map info

Can't have a space in property names.

> +
> +Optional properties:
> +	- vcc-supply: Power supply us optional. If not defined, driver will ignore it.
> +
> +Example:
> +	ds4224@10 {
> +		compatible = "maxim,ds4424";
> +		reg = <0x10>; /* When A0, A1 pins are ground */
> +		vcc-supply = "dac_vcc_3v3";
> +		max-picoamp = <200000000>; /* 200uA */
> +		ifs-scale = <61000>;
> +		/* In order to get the correct processed data values,
> +		   these resistor values should be changed to the correct values that match the
> +		   user's system resistor values for RFS0 to RFS1.
> +		   Resistance values for rfs_resistor are listed in 100 Ohm units;
> +		   ie, 800 is 80K. Acceptable RFS values are 40K to 160K.
> +		*/
> +		min-rfs = <400>;
> +		max-rfs = <1600>;
> +		rfs-resistors = <400 800 1000 1600>;
> +		dac-iio-map =

Doesn't match above doc.

> +		/*	consumer_dev_name, consumer_channel, adc_channel_label */
> +			"ds4424_dac-consumer-dev_name-1", "ds4424_dac1", "OUT1",
> +			"ds4424_dac-consumer-dev_name-2", "ds4424_dac2", "OUT2",
> +			"ds4424_dac-consumer-dev_name-3", "ds4424_dac3", "OUT3",
> +			"ds4424_dac-consumer-dev_name-4", "ds4424_dac4", "OUT4";
> +	};