Re: [PATCH] iio: imu: inv_mpu6050: check for temp_fifo_enable

[Jonathan Cameron <jic23@kernel.org>]

On Thu, 13 Aug 2020 08:04:06 +0000
Jean-Baptiste Maneyrol <JManeyrol@invensense.com> wrote:

> Hello,
> 
> this is a case that should never be happening since available scan mask only 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 temperature compensation).
> 
> So I think we can let this check as it is currently, since this is not a supported configuration.
> 

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
> 
> 
> 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>; Michał Mirosław <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 
>  
>  CAUTION: This email originated from outside of the organization. Please make sure the sender is who they say they are and do not click links or open attachments unless you recognize the sender and know the content is safe.
> 
> 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
> >         nb = fifo_count / bytes_per_datum;
> >              ~~~~~~~~~~~^~~~~~~~~~~~~~~~~
> >
> > This is a false positive.
> > Dividing by 0 is protected by this check
> >
> >         if (!(st->chip_config.accl_fifo_enable |
> >                 st->chip_config.gyro_fifo_enable |
> >                 st->chip_config.magn_fifo_enable))
> >                 goto end_session;
> >         bytes_per_datum = 0;
> >
> > But there is another fifo, temp_fifo
> >
> >         if (st->chip_config.temp_fifo_enable)
> >                 bytes_per_datum += INV_MPU6050_BYTES_PER_TEMP_SENSOR;
> >
> > Which would be skipped if it was the only enabled fifo.
> > So add to the check.
> >  
> 
> > Fixes: 2e4c0a5e2576 ("iio: imu: inv_mpu6050: add fifo temperature data support")
> >
> > Signed-off-by: Tom Rix <trix@redhat.com>  
> 
> There shouldn't be a blank line in between.
> 
> Other than that,
> Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
> 
> 
> 
> > ---
> >  drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c | 1 +
> >  1 file changed, 1 insertion(+)
> >
> > diff --git a/drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c b/drivers/iio/imu/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)
> >
> >         if (!(st->chip_config.accl_fifo_enable |
> >                 st->chip_config.gyro_fifo_enable |
> > +               st->chip_config.temp_fifo_enable |
> >                 st->chip_config.magn_fifo_enable))
> >                 goto end_session;
> >         bytes_per_datum = 0;
> > --
> > 2.18.1
> >  
> 
> 
> --
> With Best Regards,
> Andy Shevchenko