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: <48d5a091cdccb60b5f95d142cbf6df0b16ca4987.camel@baylibre.com>
Date: Mon, 19 Jan 2026 10:06:36 +0100
From: Francesco Lavra <flavra@...libre.com>
To: Jonathan Cameron <jic23@...nel.org>, Lorenzo Bianconi
 <lorenzo@...nel.org>
Cc: 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 Fri, 2026-01-16 at 19:47 +0000, Jonathan Cameron wrote:
> 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 :)

I'm keeping this as is, since there are pros and cons to changing it

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