Re: [PATCH v2 2/4] iio: imu: inv_icm42600: warn on whoami mismatch instead of failing probe

[Jonathan Cameron <jic23@kernel.org>]

On Tue, 28 Jul 2026 17:51:57 +0100
Conor Dooley <conor@kernel.org> wrote:

> On Fri, Jul 24, 2026 at 10:27:06PM +0200, Jorijn van der Graaf wrote:
> > A WHOAMI value differing from the one the compatible implies aborts
> > probe with -ENODEV, which prevents a register-compatible part described
> > with a fallback compatible from probing at all.
> > 
> > The devicetree compatible is authoritative for which part is fitted:
> > demote the mismatch to a warning and continue, as st_sensors does since
> > commit a3c2c5c937ed ("iio: st_sensors: relax WhoAmI check in
> > st_sensors_verify_id()"). This changes the probe outcome on mismatch
> > for all parts the driver supports.
> > 
> > Tested via a backport to a Fairphone 6 running a 7.1-based kernel: its
> > ICM-42630 (WHOAMI 0x0C), described with an icm42631 fallback compatible
> > and matched as icm42631, warns once and probes, and accelerometer,
> > gyroscope and temperature reads work.
> > 
> > Suggested-by: Conor Dooley <conor@kernel.org>  
> 
> I don't want this to warn, I want it gone. Fallback use should not
> produce a warning.

We've had enough problems with 'supposed' like for like replacements
in the past that were anything but that I've been allowing some type of print.

Don't mind it being a dev_info() though if that works for you.
Some have I think gone as far as dev_dbg() which would be fine from my 
point of view as well.

Jonathan

> 
> > Link: https://lore.kernel.org/all/20260722-creature-volley-0f083b904c1d@spud/
> > Assisted-by: Claude:claude-fable-5
> > Signed-off-by: Jorijn van der Graaf <jorijnvdgraaf@catcrafts.net>
> > ---
> > New in v2.
> >  drivers/iio/imu/inv_icm42600/inv_icm42600_core.c | 8 +++-----
> >  1 file changed, 3 insertions(+), 5 deletions(-)
> > 
> > diff --git a/drivers/iio/imu/inv_icm42600/inv_icm42600_core.c b/drivers/iio/imu/inv_icm42600/inv_icm42600_core.c
> > index dc97d8a274e3..f306e3ffca48 100644
> > --- a/drivers/iio/imu/inv_icm42600/inv_icm42600_core.c
> > +++ b/drivers/iio/imu/inv_icm42600/inv_icm42600_core.c
> > @@ -509,11 +509,9 @@ static int inv_icm42600_setup(struct inv_icm42600_state *st,
> >  	ret = regmap_read(st->map, INV_ICM42600_REG_WHOAMI, &val);
> >  	if (ret)
> >  		return ret;
> > -	if (val != hw->whoami) {
> > -		dev_err(dev, "invalid whoami %#02x expected %#02x (%s)\n",
> > -			val, hw->whoami, hw->name);
> > -		return -ENODEV;
> > -	}
> > +	if (val != hw->whoami)
> > +		dev_warn(dev, "unexpected whoami %#02x, expected %#02x (%s)\n",
> > +			 val, hw->whoami, hw->name);
> >  	st->name = hw->name;
> >  
> >  	/* reset to make sure previous state are not there */
> > -- 
> > 2.55.0
> >