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Subject: Re: [PATCH v2 3/4] iio: vcnl4000: Export near level property for
 proximity sensor
To:     =?UTF-8?Q?Guido_G=c3=bcnther?= <agx@sigxcpu.org>,
        Tomas Novotny <tomas@novotny.cz>,
        Jonathan Cameron <jic23@kernel.org>,
        Hartmut Knaack <knaack.h@gmx.de>,
        Peter Meerwald-Stadler <pmeerw@pmeerw.net>,
        "Angus Ainslie (Purism)" <angus@akkea.ca>,
        Marco Felsch <m.felsch@pengutronix.de>,
        Thomas Gleixner <tglx@linutronix.de>,
        linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org,
        devicetree@vger.kernel.org
References: <cover.1584380360.git.agx@sigxcpu.org>
 <5566fe01df933d3281f058666e2147cb97b38126.1584380360.git.agx@sigxcpu.org>
From:   Lars-Peter Clausen <lars@metafoo.de>
Message-ID: <c787921f-c412-4986-14ea-e31b531d3d5b@metafoo.de>
Date:   Mon, 16 Mar 2020 19:23:01 +0100
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On 3/16/20 6:46 PM, Guido Günther wrote:
> [...]
> +static ssize_t vcnl4000_read_near_level(struct iio_dev *indio_dev,
> +					uintptr_t priv,
> +					const struct iio_chan_spec *chan,
> +					char *buf)
> +{
> +	struct vcnl4000_data *data = iio_priv(indio_dev);
> +
> +	return sprintf(buf, "%u\n", data->near_level);
> +}
> +
> +static const struct iio_chan_spec_ext_info vcnl4000_ext_info[] = {
> +	{
> +		.name = "near_level",

Generally having properties with a underscore in them breaks generic 
parsing of the property name by userspace applications. This is because 
we use underscores to separate different components (type, modifier, 
etc.) of the attribute from each other.

Do you think calling this "nearlevel" would work?

I know there are existing bad examples of properties that use an 
underscore, but we should try to limit introducing new ones.

> +		.shared = IIO_SEPARATE,
> +		.read = vcnl4000_read_near_level,
> +	},
> +	{ /* sentinel */ }
> +};
> +
>   static const struct iio_chan_spec vcnl4000_channels[] = {
>   	{
>   		.type = IIO_LIGHT,
> @@ -350,6 +371,7 @@ static const struct iio_chan_spec vcnl4000_channels[] = {
>   	}, {
>   		.type = IIO_PROXIMITY,
>   		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
> +		.ext_info = vcnl4000_ext_info,
>   	}
>   };
>   
> @@ -439,6 +461,10 @@ static int vcnl4000_probe(struct i2c_client *client,
>   	dev_dbg(&client->dev, "%s Ambient light/proximity sensor, Rev: %02x\n",
>   		data->chip_spec->prod, data->rev);
>   
> +	if (device_property_read_u32(&client->dev, "near-level",
> +				     &data->near_level) < 0)
> +		data->near_level = 0;
> +
>   	indio_dev->dev.parent = &client->dev;
>   	indio_dev->info = &vcnl4000_info;
>   	indio_dev->channels = vcnl4000_channels;