linux-kernel - Re: [PATCH v2 1/2] platform/x86:dell-laptop: Add knobs to change battery charge settings

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Message-ID: <8fde7bae-b4e3-458e-8edc-22199f8bc7e2@gmx.de>
Date: Fri, 26 Jul 2024 20:42:26 +0200
From: Armin Wolf <W_Armin@....de>
To: Andres Salomon <dilinger@...ued.net>, Pali Rohár
 <pali@...nel.org>
Cc: linux-kernel@...r.kernel.org, platform-driver-x86@...r.kernel.org,
 Matthew Garrett <mjg59@...f.ucam.org>, Sebastian Reichel <sre@...nel.org>,
 Hans de Goede <hdegoede@...hat.com>,
 Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
 linux-pm@...r.kernel.org, Dell.Client.Kernel@...l.com
Subject: Re: [PATCH v2 1/2] platform/x86:dell-laptop: Add knobs to change
 battery charge settings

Am 26.07.24 um 06:25 schrieb Andres Salomon:

> On Fri, 26 Jul 2024 02:04:09 +0200
> Pali Rohár <pali@...nel.org> wrote:
>
>> On Friday 26 July 2024 01:48:50 Armin Wolf wrote:
>>> Am 26.07.24 um 00:15 schrieb Pali Rohár:
>>>
>>>> On Thursday 25 July 2024 16:24:57 Andres Salomon wrote:
>>>>> On Thu, 25 Jul 2024 01:01:58 +0200
>>>>> Pali Rohár <pali@...nel.org> wrote:
>>>>>
>>>>>> On Wednesday 24 July 2024 18:23:18 Andres Salomon wrote:
> [...]
>>>>>> The issue here is: how to tell kernel that the particular
>>>>>> dell_battery_hook has to be bound with the primary battery?
>>>>>>
>>>>> So from userspace, we've got the expectation that multiple batteries
>>>>> would show up as /sys/class/power_supply/BAT0, /sys/class/power_supply/BAT1,
>>>>> and so on.
>>>> Yes, I hope so.
>>>>
>>>>> The current BAT0 entry shows things like 'capacity' even without this
>>>>> patch, and we're just piggybacking off of that to add charge_type and
>>>>> other entries. So there shouldn't be any confusion there, agreed?
>>>> I have not looked at the battery_hook_register() code yet (seems that I
>>>> would have to properly read it and understand it). But does it mean that
>>>> battery_hook_register() is adding hook just for "BAT0"?
>>>>
>>>> What I mean: cannot that hook be registered to "BAT1" too? Because if
>>>> yes then we should prevent it. Otherwise this hook which is for "Dell
>>>> Primary Battery" could be registered also for secondary battery "BAT1".
>>>> (I hope that now it is more clear what I mean).
>>> Hi,
>>>
>>> the battery hook is being registered to all ACPI batteries present on a given system,
>>> so you need to do some manual filtering when .add_battery() is called.
>> Ok. So it means that the filtering based on the primary battery in
>> add_battery callback is needed.
>>
> Thanks for the explanations. Seems simple enough to fix that, as some of
> the other drivers are checking battery->desc->name for "BAT0".
>
>
> One thing that I keep coming back to, and was reinforced as I looked at
> include/linux/power_supply.h; the generic power supply charge_type has
> values that are very close to Dells, but with different names. I could
> shoehorn them in, though, with the following mappings:
>
> POWER_SUPPLY_CHARGE_TYPE_FAST,         => "express" (aka ExpressCharge)
> POWER_SUPPLY_CHARGE_TYPE_STANDARD,     => "standard"
> POWER_SUPPLY_CHARGE_TYPE_ADAPTIVE,     => "adaptive"
> POWER_SUPPLY_CHARGE_TYPE_CUSTOM,       => "custom"
> POWER_SUPPLY_CHARGE_TYPE_LONGLIFE,     => "primarily_ac"
>
> The main difference is that Primarily AC is described and documented as
> slightly different than Long Life, but I suspect the result is roughly
> the same thing. And the naming "Fast" and "Long Life" wouldn't match the
> BIOS naming of "ExpressCharge" and "Primarily AC".
>
> Until now I've opted to match the BIOS naming, but I'm curious what others
> think before I send V3 of the patches.

I agree that POWER_SUPPLY_CHARGE_TYPE_FAST should be mapped the ExpressCharge,
but i think that "primarily_ac" should become a official power supply charging mode.

The reason is that for example the wilco-charger driver also supports such a charging mode
(currently reported as POWER_SUPPLY_CHARGE_TYPE_TRICKLE) and the charging mode seems to be
both sufficiently different from POWER_SUPPLY_CHARGE_TYPE_LONGLIFE/POWER_SUPPLY_CHARGE_TYPE_TRICKLE
and sufficiently generic to be supported by a wide array of devices.

Thanks,
Armin Wolf