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Date:   Sun, 16 Aug 2020 09:58:30 +0100
From:   Jonathan Cameron <jic23@kernel.org>
To:     Jean-Baptiste Maneyrol <JManeyrol@invensense.com>
Cc:     Andy Shevchenko <andy.shevchenko@gmail.com>,
        "trix@redhat.com" <trix@redhat.com>,
        Hartmut Knaack <knaack.h@gmx.de>,
        Lars-Peter Clausen <lars@metafoo.de>,
        Peter Meerwald <pmeerw@pmeerw.net>,
        =?UTF-8?B?TWljaGE=?= =?UTF-8?B?xYIgTWlyb3PFgmF3?= 
        <mirq-linux@rere.qmqm.pl>, Lee Jones <lee.jones@linaro.org>,
        linux-iio <linux-iio@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] iio: imu: inv_mpu6050: check for temp_fifo_enable
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On Thu, 13 Aug 2020 08:04:06 +0000
Jean-Baptiste Maneyrol <JManeyrol@invensense.com> wrote:

> Hello,
>=20
> this is a case that should never be happening since available scan mask o=
nly advertise Accel + Temp, Gyro + Temp, or Accel + Gyro + Temp.
> More than that, temperature sensor is not working when MEMS engine is off=
. (it's only purpose it to measure temperature of the MEMS to do data tempe=
rature compensation).
>=20
> So I think we can let this check as it is currently, since this is not a =
supported configuration.
>=20

Perhaps a good option would be to add a suitably positioned comment to make
this clear so we don't get further patches 'fixing' this in the future?

Thanks,

Jonathan

> Best regards,
> JB
>=20
>=20
> From: Andy Shevchenko <andy.shevchenko@gmail.com>
> Sent: Monday, August 10, 2020 10:02
> To: trix@redhat.com <trix@redhat.com>
> Cc: Jonathan Cameron <jic23@kernel.org>; Hartmut Knaack <knaack.h@gmx.de>=
; Lars-Peter Clausen <lars@metafoo.de>; Peter Meerwald <pmeerw@pmeerw.net>;=
 Jean-Baptiste Maneyrol <JManeyrol@invensense.com>; Micha=C5=82 Miros=C5=82=
aw <mirq-linux@rere.qmqm.pl>; Lee Jones <lee.jones@linaro.org>; linux-iio <=
linux-iio@vger.kernel.org>; Linux Kernel Mailing List <linux-kernel@vger.ke=
rnel.org>
> Subject: Re: [PATCH] iio: imu: inv_mpu6050: check for temp_fifo_enable=20
> =C2=A0
> =C2=A0CAUTION: This email originated from outside of the organization. Pl=
ease make sure the sender is who they say they are and do not click links o=
r open attachments unless you recognize the sender and know the content is =
safe.
>=20
> On Sun, Aug 9, 2020 at 7:00 PM <trix@redhat.com> wrote:
> >
> > From: Tom Rix <trix@redhat.com>
> >
> > clang static analysis reports this problem
> >
> > inv_mpu_ring.c:181:18: warning: Division by zero
> >=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 nb =3D fifo_count / byt=
es_per_datum;
> >=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0 ~~~~~~~~~~~^~~~~~~~~~~~~~~~~
> >
> > This is a false positive.
> > Dividing by 0 is protected by this check
> >
> >=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 if (!(st->chip_config.a=
ccl_fifo_enable |
> >=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0 st->chip_config.gyro_fifo_enable |
> >=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0 st->chip_config.magn_fifo_enable))
> >=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0 goto end_session;
> >=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 bytes_per_datum =3D 0;
> >
> > But there is another fifo, temp_fifo
> >
> >=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 if (st->chip_config.tem=
p_fifo_enable)
> >=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0 bytes_per_datum +=3D INV_MPU6050_BYTES_PER_TEMP_SE=
NSOR;
> >
> > Which would be skipped if it was the only enabled fifo.
> > So add to the check.
> > =20
>=20
> > Fixes: 2e4c0a5e2576 ("iio: imu: inv_mpu6050: add fifo temperature data =
support")
> >
> > Signed-off-by: Tom Rix <trix@redhat.com> =20
>=20
> There shouldn't be a blank line in between.
>=20
> Other than that,
> Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
>=20
>=20
>=20
> > ---
> >=C2=A0 drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c | 1 +
> >=C2=A0 1 file changed, 1 insertion(+)
> >
> > diff --git a/drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c b/drivers/iio/i=
mu/inv_mpu6050/inv_mpu_ring.c
> > index b533fa2dad0a..5240a400dcb4 100644
> > --- a/drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c
> > +++ b/drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c
> > @@ -141,6 +141,7 @@ irqreturn_t inv_mpu6050_read_fifo(int irq, void *p)
> >
> >=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 if (!(st->chip_config.a=
ccl_fifo_enable |
> >=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0 st->chip_config.gyro_fifo_enable |
> > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0 st->chip_config.temp_fifo_enable |
> >=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0 st->chip_config.magn_fifo_enable))
> >=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0 goto end_session;
> >=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 bytes_per_datum =3D 0;
> > --
> > 2.18.1
> > =20
>=20
>=20
> --
> With Best Regards,
> Andy Shevchenko