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

[Conor Dooley <conor@kernel.org>]

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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.

> 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
> 

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