Re: [PATCH] iio: temperature: mlx90614: Fix dual channel probe condition check

[Crt Mori]

Hi,
No objections, but I wanted to test it and can't find the time for
this sorry. I don't think I have seen a single channel MLX90614 when I
wrote a driver, so maybe that is something that came with 90615
patches or later.

Best regards,
Crt

On Mon, 19 Oct 2026 at 05:01, Jonathan Cameron <jic23@xxxxxxxxxx> wrote:
>
> On Thu, 17 Sep 2026 14:16:15 +0100
> Salah Triki <salah.triki@xxxxxxxxx> wrote:
>
> > Hi Crt,
> >
> > Thanks for your feedback.
> >
> > Actually, the patch primarily fixes the behavior for the MLX90614.
> >
> > In the current codebase, MLX90614 has `chip_info->dual_channel = true`.
> > Because `mlx90614_probe_num_ir_sensors()` checks
> > `if (chip_info->dual_channel)`, it returns 0 immediately for MLX90614
> > without reading the EEPROM CONFIG1 register. As a result, dual-channel
> > MLX90614 sensors are incorrectly registered as single-channel devices.
> >
> > For MLX90615 (`dual_channel = false`), the condition was bypassed, causing
> > an unnecessary SMBus read to EEPROM CONFIG1, even though MLX90615 only
> > supports a single object channel.
> >
> > By changing the check to `if (!chip_info->dual_channel)`, we fix both
> > issues:
> > 1. MLX90614 correctly reads EEPROM CONFIG1 to detect whether it operates
> > in single or dual channel mode.
> > 2. MLX90615 skips the EEPROM read entirely.
> >
> > I don't have physical hardware to test this on; this bug was spotted via
> > code inspection.
>
> Explanation makes sense to me and as Crt hasn't come back with
> a reply, I'll assuming Crt has no objections (shout if not!)
>
> Applied and marked stable
>
> Thanks,
>
> Jonathan
>
> >
> > Best regards,
> > Salah
> >
> > On Thu, Sep 17, 2026 at 01:27:48PM +0200, Crt Mori wrote:
> > > So this fix is for the MLX90615, which is registered as single channel
> > > operation? Did you test on 90614 as well?
> > >
> > > Best regards,
> > > Crt
> > >
> > > Crt Mori
> > >
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> > >
> > > On Thu, 17 Sept 2026 at 13:01, Salah Triki <salah.triki@xxxxxxxxx> wrote:
> > > >
> > > > In mlx90614_probe_num_ir_sensors(), the check on chip_info->dual_channel
> > > > is inverted.
> > > >
> > > > Currently, if dual_channel is true (MLX90614), the function returns 0
> > > > immediately without checking op_eeprom_config1. This forces all MLX90614
> > > > devices to be registered as single sensor (num_channels = 2), making the
> > > > second object temperature channel inaccessible.
> > > >
> > > > Conversely, if dual_channel is false (MLX90615), the function skips the
> > > > early return and performs an unnecessary SMBus read on EEPROM CONFIG1 even
> > > > though MLX90615 does not support dual channel operation.
> > > >
> > > > Fix this by negating the condition so that single-channel chips return
> > > > early with 0, while dual-channel capable chips (MLX90614) proceed to read
> > > > the EEPROM configuration register to detect whether 1 or 2 object channels
> > > > are present.
> > > >
> > > > Fixes: 3d5ead238bc8 ("iio: mlx90614: Factor our register IO and constants into model specific descriptor")
> > > > Assisted-by: LLM
> > > > Signed-off-by: Salah Triki <salah.triki@xxxxxxxxx>
> > > > ---
> > > >  drivers/iio/temperature/mlx90614.c | 2 +-
> > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > >
> > > > diff --git a/drivers/iio/temperature/mlx90614.c b/drivers/iio/temperature/mlx90614.c
> > > > index 27d6ab5f5d7a..4f79da1f905e 100644
> > > > --- a/drivers/iio/temperature/mlx90614.c
> > > > +++ b/drivers/iio/temperature/mlx90614.c
> > > > @@ -565,7 +565,7 @@ static int mlx90614_probe_num_ir_sensors(struct i2c_client *client)
> > > >         const struct mlx_chip_info *chip_info = data->chip_info;
> > > >         s32 ret;
> > > >
> > > > -       if (chip_info->dual_channel)
> > > > +       if (!chip_info->dual_channel)
> > > >                 return 0;
> > > >
> > > >         ret = i2c_smbus_read_word_data(client, chip_info->op_eeprom_config1);
> > > > --
> > > > 2.43.0
> > > >
>