linux-kernel - Re: [PATCH v2 1/3] iio: imu: st_lsm6dsx: Set FIFO ODR for accelerometer and gyroscope only

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Message-ID: <20260116194738.48b6e3ff@jic23-huawei>
Date: Fri, 16 Jan 2026 19:47:38 +0000
From: Jonathan Cameron <jic23@...nel.org>
To: Lorenzo Bianconi <lorenzo@...nel.org>
Cc: Francesco Lavra <flavra@...libre.com>, David Lechner
 <dlechner@...libre.com>, Nuno Sá <nuno.sa@...log.com>, Andy
 Shevchenko <andy@...nel.org>, linux-iio@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/3] iio: imu: st_lsm6dsx: Set FIFO ODR for
 accelerometer and gyroscope only

On Thu, 15 Jan 2026 14:13:01 +0100
Lorenzo Bianconi <lorenzo@...nel.org> wrote:

> > The st_lsm6dsx_set_fifo_odr() function, which is called when enabling and
> > disabling the hardware FIFO, checks the contents of the hw->settings->batch
> > array at index sensor->id, and then sets the current ODR value in sensor
> > registers that depend on whether the register address is set in the above
> > array element. This logic is valid for internal sensors only, i.e. the
> > accelerometer and gyroscope; however, since commit c91c1c844ebd ("iio: imu:
> > st_lsm6dsx: add i2c embedded controller support"), this function is called
> > also when configuring the hardware FIFO for external sensors (i.e. sensors
> > accessed through the sensor hub functionality), which can result in
> > unrelated device registers being written.
> > 
> > Add a check to the beginning of st_lsm6dsx_set_fifo_odr() so that it does
> > not touch any registers unless it is called for internal sensors.
> > 
> > Fixes: c91c1c844ebd ("iio: imu: st_lsm6dsx: add i2c embedded controller support")
> > Signed-off-by: Francesco Lavra <flavra@...libre.com>
> > ---
> >  drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c | 4 ++++
> >  1 file changed, 4 insertions(+)
> > 
> > diff --git a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c
> > index 55d877745575..1ee2fc5f5f1f 100644
> > --- a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c
> > +++ b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c
> > @@ -225,6 +225,10 @@ static int st_lsm6dsx_set_fifo_odr(struct st_lsm6dsx_sensor *sensor,
> >  	const struct st_lsm6dsx_reg *batch_reg;
> >  	u8 data;
> >  
> > +	/* Only internal sensors have a FIFO ODR configuration register. */
> > +	if (sensor->id >= ARRAY_SIZE(hw->settings->batch))
> > +		return 0;  
> 
> I guess it is more clear to check if the sensor is acc or gyro here.
> What do you think? Something like:
> 
> 	if (sensor->id != ST_LSM6DSX_ID_GYRO &&
> 	    sensor->id != ST_LSM6DSX_ID_ACC)
> 	    return 0;

Disadvantage is that to check for overflow we have to know those are 0 and 1.
I'm not sure which is better of the two here. One is more logically correct
the other is easier to review :)

> 
> Regards,
> Lorenzo
> 
> > +
> >  	batch_reg = &hw->settings->batch[sensor->id];
> >  	if (batch_reg->addr) {
> >  		int val;
> > -- 
> > 2.39.5
> >