Re: [PATCH] platform/x86: msi-ec: Report valid charge thresholds when unset

[Ilpo Järvinen]

On Wed, 16 Sep 2026, Daasaradhi Mannava wrote:

> The charge thresholds are computed by subtracting a fixed offset from
> the raw EC value. When no charge limit has been set, the EC can hold a
> value below range_min (0x80 on an MSI GL65 Leopard 9SCXK), and reading
> the sysfs attributes returns nonsense:
> 
>   charge_control_start_threshold: -10
>   charge_control_end_threshold:   0
> 
> Both attributes are documented to be within 0 - 100, and an end
> threshold of 0 wrongly suggests that charging is disabled.
> 
> The store path already rejects values outside range_min..range_max.
> Apply the same range to the show path and report the maximum threshold
> for any value outside of it.
> 
> Tested on an MSI GL65 Leopard 9SCXK (EC firmware 16U8EMS2.100) with
> the EC holding 0x80: the attributes now read 90 and 100.
> 
> Fixes: 392cacf2aa10 ("platform/x86: Add new msi-ec driver")
> Assisted-by: LLM
> Signed-off-by: Daasaradhi Mannava <daasaradhimannava@xxxxxxxxx>
> ---
>  drivers/platform/x86/msi-ec.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/drivers/platform/x86/msi-ec.c b/drivers/platform/x86/msi-ec.c
> index 566dfc73c..1762551e0 100644
> --- a/drivers/platform/x86/msi-ec.c
> +++ b/drivers/platform/x86/msi-ec.c
> @@ -1279,6 +1279,15 @@ static ssize_t charge_control_threshold_show(u8 offset,
>  	if (result < 0)
>  		return result;
>  
> +	/*
> +	 * The EC may hold an out-of-range value (e.g. 0x80) when no charge
> +	 * limit has been set. Report the maximum threshold instead of a
> +	 * meaningless (possibly negative) percentage.
> +	 */
> +	if (rdata < conf.charge_control.range_min ||
> +	    rdata > conf.charge_control.range_max)
> +		rdata = conf.charge_control.range_max;
> +
>  	return sysfs_emit(buf, "%i\n", rdata - offset);
>  }

Hi,

This seems similar to case in commits:

186bf9031666 ("platform/x86: asus-wmi: do not enforce a battery charge threshold")
78bf392ba77d ("platform/x86: asus-wmi: temporarily revert to setting a charge limit")

(The latter reverts first one as userspace could not handle -ENODATA but 
thought the feature was available.)

So ideally, I'd tend to think we'd want to return -ENODATA when the 
threshold hasn't been set. But whether userspace survives that is a 
question we cannot ignore.

-- 
 i.