Re: [PATCH v4 1/2] iio: light: cm3323: fix reg_conf not being initialized correctly

[Jonathan Cameron <jic23@kernel.org>]

On Sun, 26 Jul 2026 13:44:19 +0200
Aldo Conte <aldocontelk@gmail.com> wrote:

> On 20/04/26 19:53, Jonathan Cameron wrote:
> > On Tue,  7 Apr 2026 17:17:01 +0200
> > Aldo Conte <aldocontelk@gmail.com> wrote:
> >   
> >> The code stores the return value of i2c_smbus_write_word_data()
> >> in data->reg_conf; however, this value represents the result
> >> of the write operation and not the value actually written to
> >> the configuration register. This meant that the contents of
> >> data->reg_conf did not truly reflect the contents
> >> of the hardware register.
> >>
> >> Instead, save the value of the register before the write
> >> and use this value in the I2C write.
> >>
> >> The bug was found by code inspection: i2c_smbus_write_word_data()
> >> returns 0 on success, not the value written to the register.
> >>
> >> Tested using i2c-stub on a Raspberry Pi 3B running a custom 6.19.10
> >> kernel. Before loading the driver, the configuration register 0x00
> >> CM3323_CMD_CONF was populated with 0x0030 using
> >> `i2cset -y 11 0x10 0x00 0x0030 w`, encoding an integration time of 320ms
> >> in bits[6:4].
> >>
> >> Due to incorrect initialization of data->reg_conf in
> >> cm3323_init(), the print of integration_time returns 0.040000
> >> instead of the expected 0.320000. This happens because the read of the
> >> integration_time depends on cm3323_get_it_bits() that is based on the
> >> value of data->reg_conf, which is erroneously set to 0.
> >>
> >> With this fix applied, data->reg_conf correctly saves 0x0030 after init
> >> and the successive integration_time reports 0.320000 as expected.
> >>
> >> Fixes: 8b0544263761 ("iio: light: Add support for Capella CM3323 color sensor")
> >> Cc: stable@vger.kernel.org
> >> Signed-off-by: Aldo Conte <aldocontelk@gmail.com>  
> > Applied this patch, but patch 2 will need to wait for this to make its way
> > into upstream - probably middle of the next cycle before that is in place.
> > 
> > thanks,
> > 
> > Jonathan
> >   
> 
> Hi Jonathan,
> 
> The fix this depended on (commit 1f4f0bcc5255 "iio: light: cm3323: fix
> reg_conf not being initialized correctly") has since landed in mainline.
> 
> Is there anything still needed on my side for patch 2 (iio: light: cm3323: use 
> dev_err_probe() in probe path) to proceed?
Good thing you checked - I'd marked it wrong in patchwork and so had lost
track of it :(

Fixed that now and applied to the testing branch of iio.git

Thanks

Jonathan



> 
> Thanks,
> Aldo
>