Re: [PATCH 1/2] hwmon: (macsmc) Fix regressions in Apple Silicon SMC hwmon driver

[James Calligeros <jcalligeros99@gmail.com>]

On Friday, 30 January 2026 3:51:10 am Australian Eastern Standard Time
Guenter Roeck wrote:
> The recently added macsmc-hwmon driver contained several critical
> bugs in its sensor population logic and float conversion routines.
> 
> Specifically:
> - The voltage sensor population loop used the wrong prefix ("volt-"
>   instead of "voltage-") and incorrectly assigned sensors to the
>   temperature sensor array (hwmon->temp.sensors) instead of the
>   voltage sensor array (hwmon->volt.sensors). This would lead to
>   out-of-bounds memory access or data corruption when both temperature
>   and voltage sensors were present.
> - The float conversion in macsmc_hwmon_write_f32() had flawed exponent
>   logic for values >= 2^24 and lacked masking for the mantissa, which
>   could lead to incorrect values being written to the SMC.
> 
> Fix these issues to ensure correct sensor registration and reliable
> manual fan control.
> 
> Confirm that the reported overflow in FIELD_PREP is fixed by declaring
> macsmc_hwmon_write_f32() as __always_inline for a compile test.
> 
> Fixes: 785205fd8139 ("hwmon: Add Apple Silicon SMC hwmon driver")
> Reported-by: Nathan Chancellor <nathan@kernel.org>
> Closes: https://lore.kernel.org/linux-hwmon/20260119195817.GA1035354@ax162/
> Cc: James Calligeros <jcalligeros99@gmail.com>
> Cc: Nathan Chancellor <nathan@kernel.org>
> Cc: Neal Gompa <neal@gompa.dev>
> Cc: Janne Grunau <j@jannau.net>
> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
> ---
>  drivers/hwmon/macsmc-hwmon.c | 23 ++++++++++-------------
>  1 file changed, 10 insertions(+), 13 deletions(-)
> 

Reviewed-by: James Calligeros <jcalligeros99@gmail.com> for the series.

It would be helpful to Cc the Asahi list as per MAINTAINERS in the
future; any one of us could have reviewed and tested these two patches while
I had been unable to[1].

Regards,
James

[1] https://lore.kernel.org/asahi/CAHgNfTynZHNt3=JY82-WPR1b_1JyoJ=hnazcPwJtSStOZsA1=g@mail.gmail.com/