linux-kernel - Re: [PATCH] iio: imu: st_lsm6dsx: Fix check for invalid samples from FIFO

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Message-ID: <0168c543e320aeacbbdcdd7f4f3bb0edb81b79f4.camel@baylibre.com>
Date: Wed, 21 Jan 2026 15:05:54 +0100
From: Francesco Lavra <flavra@...libre.com>
To: Andy Shevchenko <andriy.shevchenko@...el.com>
Cc: Lorenzo Bianconi <lorenzo@...nel.org>, Jonathan Cameron
 <jic23@...nel.org>,  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] iio: imu: st_lsm6dsx: Fix check for invalid samples
 from FIFO

On Wed, 2026-01-21 at 14:47 +0200, Andy Shevchenko wrote:
> On Wed, Jan 21, 2026 at 12:27:57PM +0100, Francesco Lavra wrote:
> > The DRDY_MASK feature implemented in sensor chips marks gyroscope and
> > accelerometer invalid samples (i.e. samples that have been acquired
> > during
> > the settling time of sensor filters) with the special values 0x7FFFh,
> > 0x7FFE, and 0x7FFD.
> > The driver checks FIFO samples against these special values in order to
> > discard invalid samples; however, it does the check regardless of the
> > type
> > of samples being processed, whereas this feature is specific to
> > gyroscope
> > and accelerometer data. This could cause valid samples to be discarded.
> > Fix the above check so that it takes into account the type of samples
> > being
> > processed.
> 
> ...
> 
> >  st_lsm6dsx_push_tagged_data(struct st_lsm6dsx_hw *hw, u8 tag,
> >                             u8 *data, s64 ts)
> >  {
> > -       s16 val = le16_to_cpu(*(__le16 *)data);
> >         struct st_lsm6dsx_sensor *sensor;
> >         struct iio_dev *iio_dev;
> >  
> >         /* invalid sample during bootstrap phase */
> > -       if (val >= ST_LSM6DSX_INVALID_SAMPLE)
> > +       if ((tag == ST_LSM6DSX_GYRO_TAG || tag == ST_LSM6DSX_ACC_TAG)
> > &&
> > +           (s16)le16_to_cpup((__le16 *)data) >=
> > ST_LSM6DSX_INVALID_SAMPLE)
> 
> Since data is u8 *, it might appear on unaligned addresses and the proper
> conversion here is to use get_unaligned_le16() without any of those ugly
> castings.

data here corresponds to iio_buff in st_lsm6dsx_read_tagged_fifo(), which
is declared as __aligned(8), so it cannot appear on unaligned addresses.

> >                 return -EINVAL;
>