linux-kernel - Re: [PATCH v6 6/7] iio: adc: Add support for AD4000

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Message-ID: <5c7fcaa93c8184dd62beeccccfa07e144042fdc4.camel@gmail.com>
Date: Tue, 09 Jul 2024 09:41:18 +0200
From: Nuno Sá <noname.nuno@...il.com>
To: Marcelo Schmitt <marcelo.schmitt@...log.com>, broonie@...nel.org, 
 lars@...afoo.de, Michael.Hennerich@...log.com, jic23@...nel.org, 
 robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
  nuno.sa@...log.com, dlechner@...libre.com, corbet@....net, 
 marcelo.schmitt1@...il.com
Cc: linux-iio@...r.kernel.org, devicetree@...r.kernel.org, 
	linux-spi@...r.kernel.org, linux-doc@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 6/7] iio: adc: Add support for AD4000

On Sat, 2024-06-29 at 16:06 -0300, Marcelo Schmitt wrote:
> Add support for AD4000 series of low noise, low power, high speed,
> successive approximation register (SAR) ADCs.
> 
> Signed-off-by: Marcelo Schmitt <marcelo.schmitt@...log.com>
> ---

Hi Marcelo,

LGTM. Only one thing that needs to be addressed. With that,

Reviewed-by: Nuno Sa <nuno.sa@...log.com>

>  MAINTAINERS              |   1 +
>  drivers/iio/adc/Kconfig  |  12 +
>  drivers/iio/adc/Makefile |   1 +
>  drivers/iio/adc/ad4000.c | 708 +++++++++++++++++++++++++++++++++++++++
>  4 files changed, 722 insertions(+)
>  create mode 100644 drivers/iio/adc/ad4000.c
> 

...

> 
> +	st->gain_milli = 1000;
> +	if (chip->has_hardware_gain &&
> +	    device_property_present(dev, "adi,gain-milli")) {
> +		ret = device_property_read_u16(dev, "adi,gain-milli",
> +					       &st->gain_milli);
> +		if (ret)
> +			return dev_err_probe(dev, ret,
> +					     "Failed to read gain
> property\n");
> +	}

The above is odd. Why not reading directly device_property_read_u16()? Skip the
call to device_property_present(). 

But most importantly, you're not doing any validation on gain_milli which is an
enum (by looking at the bindings). So in theory even 0 would be accepted which
would lead to a divide by 0 later on. I would do:

if (chip->has_hardware_gain) {
	ret = device_property_read_u16(...)
	if (!ret) {
		/* validate here for a proper value /*
	}
}

You can also check for ret < 0 and -EINVAL to detect an invalid devicetree
parameter instead of completely ignoring return codes (but for non mandatory
properties one typically does not care much - up to you)

- Nuno Sá