linux-kernel - Re: [PATCH v5 05/11] iio: accel: adxl345: add freefall feature

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Message-ID: <20250331112839.78c2bc71@jic23-huawei>
Date: Mon, 31 Mar 2025 11:28:39 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: Lothar Rubusch <l.rubusch@...il.com>
Cc: lars@...afoo.de, Michael.Hennerich@...log.com,
 linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org,
 eraretuya@...il.com
Subject: Re: [PATCH v5 05/11] iio: accel: adxl345: add freefall feature

On Tue, 18 Mar 2025 23:08:37 +0000
Lothar Rubusch <l.rubusch@...il.com> wrote:

> Add the freefall detection of the sensor together with a threshold and
> time parameter. A freefall event is detected if the measuring signal
> falls below the threshold.
> 
> Introduce a freefall threshold stored in regmap cache, and a freefall
> time, having the scaled time value stored as a member variable in the
> state instance.
> 
> Signed-off-by: Lothar Rubusch <l.rubusch@...il.com>
Hi Lothar,

Apologies for the slow review!  Just catching up after travel
and I did it reverse order.

> +
> +static int adxl345_set_ff_en(struct adxl345_state *st, bool cmd_en)
> +{
> +	unsigned int regval, ff_threshold;
> +	const unsigned int freefall_mask = 0x02;

Where did this mask come from?   Feels like it should be a define
(just use ADXL345_INT_FREE_FALL probably)
or if not that at lest use BIT(1) to make it clear it's a bit rather
than the number 2.

> +	bool en;
> +	int ret;
> +
> +	ret = regmap_read(st->regmap, ADXL345_REG_THRESH_FF, &ff_threshold);
> +	if (ret)
> +		return ret;
> +
> +	en = cmd_en && ff_threshold > 0 && st->ff_time_ms > 0;
> +
> +	regval = en ? ADXL345_INT_FREE_FALL : 0x00;
> +
> +	return regmap_update_bits(st->regmap, ADXL345_REG_INT_ENABLE,
> +				  freefall_mask, regval);
> +}

Jonathan