Re: [PATCH] Documentation: sysfs-class-power: Update Long_Life description

[Hans de Goede <hansg@kernel.org>]

Hi Derek,

On 3-Aug-26 23:07, Derek J. Clark wrote:
> While adding charge limiting support to the Lenovo WMI drivers, there
> was some back and forth about whether charge_types or
> charge_control_end_threshold was the appropriate attribute to expose a
> battery charge limiting toggle that is fixed in the BIOS. The confusion
> arose because the charge_control_end_threshold description closely
> matches the functional change the hardware is making, while the
> charge_types functionality better suits the actual an on/off toggle that
> occurs in the BIOS. This specific scenario is not explicitly enumerated
> in the documentation, though it is fairly common.
> 
> Given that the original intention was to use it this way[1],[2], and that
> the samsung-laptop[3], ideapad-laptop[4], and lenovo-wmi-other[5] drivers
> all use the convention of charge_types with an exposed Long_Life and
> Standard value for this, codify it in the Documentation to avoid confusion
> in the future.
> 
> [1] https://lore.kernel.org/linux-pm/49993a42-aa91-46bf-acef-4a089db4c2db@redhat.com/
> [2] https://lore.kernel.org/platform-driver-x86/20241209204051.8786-1-hdegoede@redhat.com/
> [3] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=de2884c6cdd3d133704ce37393590dd1c761500c
> [4] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=da8f2708f9b69707f4efeb432a18395e46b4666f
> [5] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=9ca8fc065b88b327acbfdc33454efea391639716
> 
> Suggested-by: Hans de Goede <hansg@kernel.org>
> Signed-off-by: Derek J. Clark  <derekjohn.clark@gmail.com>

Thank you for updating the docs, patch looks good to me:

Reviewed-by: Hans de Goede <johannes.goede@oss.qualcomm.com>

Regards,

Hans


> ---
>  Documentation/ABI/testing/sysfs-class-power | 14 +++++++++-----
>  1 file changed, 9 insertions(+), 5 deletions(-)
> 
> diff --git a/Documentation/ABI/testing/sysfs-class-power b/Documentation/ABI/testing/sysfs-class-power
> index 5641f1fd5fd6..98b389845d1e 100644
> --- a/Documentation/ABI/testing/sysfs-class-power
> +++ b/Documentation/ABI/testing/sysfs-class-power
> @@ -365,9 +365,12 @@ Contact:	linux-pm@vger.kernel.org
>  Description:
>  		Represents a battery percentage level, above which charging will
>  		stop. Not all hardware is capable of setting this to an arbitrary
> -		percentage. Drivers will round written values to the nearest
> -		supported value. Reading back the value will show the actual
> -		threshold set by the driver.
> +		value, instead providing different minimum, maximum, or step
> +		values. Drivers will round written values to the nearest supported
> +		value. Reading back the value will show the actual threshold set
> +		by the driver. For hardware that only supports a single fixed
> +		value, use charge_types with a value of "Long Life" (vs "Standard")
> +		instead'
>  
>  		Access: Read, Write
>  
> @@ -398,8 +401,9 @@ Description:
>  			when to start and stop charging. Advanced users
>  			can use this to drastically extend battery life.
>  		Long Life:
> -			The charger reduces its charging rate in order to
> -			prolong the battery health.
> +			The charger firmware reduces its charging rate and/or
> +			maximum charging percentage to a hardware specified
> +			fixed limit in order to prolong the battery health.
>  		Bypass:
>  			The charger bypasses the charging path around the
>  			integrated converter allowing for a "smart" wall