linux-kernel - Re: [PATCH v3 8/8] iio: adc: Add events support to ad4052

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Message-ID: <20250614113616.4663269f@jic23-huawei>
Date: Sat, 14 Jun 2025 11:36:16 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: Jorge Marques <jorge.marques@...log.com>
Cc: Lars-Peter Clausen <lars@...afoo.de>, Michael Hennerich
 <Michael.Hennerich@...log.com>, Rob Herring <robh@...nel.org>, Krzysztof
 Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>,
 Jonathan Corbet <corbet@....net>, David Lechner <dlechner@...libre.com>,
 Nuno Sá <nuno.sa@...log.com>, Andy Shevchenko
 <andy@...nel.org>, Uwe Kleine-König
 <ukleinek@...nel.org>, <linux-iio@...r.kernel.org>,
 <linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>,
 <linux-doc@...r.kernel.org>, <linux-pwm@...r.kernel.org>
Subject: Re: [PATCH v3 8/8] iio: adc: Add events support to ad4052

On Tue, 10 Jun 2025 09:34:41 +0200
Jorge Marques <jorge.marques@...log.com> wrote:

> The AD4052 family supports autonomous monitoring readings for threshold
> crossings. Add support for catching the GPIO interrupt and expose as an IIO
> event. The device allows to set either, rising and falling directions. Only
> either threshold crossing is implemented.
> 
> Signed-off-by: Jorge Marques <jorge.marques@...log.com>
Hi Jorge,

A few comments inline.

Jonathan

>
> +
> +static int ad4052_write_event_config(struct iio_dev *indio_dev,
> +				     const struct iio_chan_spec *chan,
> +				     enum iio_event_type type,
> +				     enum iio_event_direction dir,
> +				     bool state)
> +{
> +	struct ad4052_state *st = iio_priv(indio_dev);
> +	int ret;
> +
> +	if (!iio_device_claim_direct(indio_dev))
> +		return -EBUSY;
> +	if (st->wait_event == state) {
> +		ret = 0;

Feels like a case where init ret at declaration would be reasonable.

> +		goto out_release;
> +	}
> +
> +	if (state)
> +		ret = ad4052_monitor_mode_enable(st);
> +	else
> +		ret = ad4052_monitor_mode_disable(st);
> +
> +	if (!ret)
> +		st->wait_event = state;
> +
> +out_release:
> +	iio_device_release_direct(indio_dev);
> +	return ret;
> +}

> +
> +static int ad4052_read_event_value(struct iio_dev *indio_dev,
> +				   const struct iio_chan_spec *chan,
> +				   enum iio_event_type type,
> +				   enum iio_event_direction dir,
> +				   enum iio_event_info info, int *val,
> +				   int *val2)
> +{
> +	struct ad4052_state *st = iio_priv(indio_dev);
> +	int ret;
> +
> +	if (!iio_device_claim_direct(indio_dev))
> +		return -EBUSY;
> +
> +	if (st->wait_event) {
> +		ret = -EBUSY;
> +		goto out_release;

Not being able to read event parameters whilst monitoring them seems
very restrictive.  Can't we cache the values?  Either play games to ensure
we get them from the regmap cache or just cache these few values in st.

Checking what you are monitoring for feels like the sort of thing
userspace might well do.

Even blocking changing the monitoring parameters is unusually strict.
Why not just drop out of monitor mode, update them and go back in?


> +	}
> +
> +	switch (info) {
> +	case IIO_EV_INFO_VALUE:
> +		ret = __ad4052_read_event_info_value(st, dir, val);
> +		break;
> +	case IIO_EV_INFO_HYSTERESIS:
> +		ret = __ad4052_read_event_info_hysteresis(st, dir, val);
> +		break;
> +	default:
> +		ret = -EINVAL;
> +		break;
> +	}
> +
> +out_release:
> +	iio_device_release_direct(indio_dev);
> +	return ret ? ret : IIO_VAL_INT;
> +}