linux-kernel - Re: [PATCH] ACPI: battery: Add "Not Charging" quirk for Microsoft Surface devices

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Date:   Fri, 6 May 2022 20:47:18 +0200
From:   Maximilian Luz <luzmaximilian@...il.com>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     Len Brown <lenb@...nel.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ACPI: battery: Add "Not Charging" quirk for Microsoft
 Surface devices

On 5/6/22 20:43, Rafael J. Wysocki wrote:
> On Fri, Apr 29, 2022 at 7:41 PM Maximilian Luz <luzmaximilian@...il.com> wrote:
>>
>> Microsoft Surface devices have a limiter that sets a fixed maximum
>> charge capacity for the battery. When that maximum capacity has been
>> reached, charging stops. In that case, _BST returns a battery state
>> field with both "charging" and "discharging" bits cleared. The battery
>> driver, however, returns "unknown" as status.
>>
>> This seems to be the same behavior as observed on the ThinkPads, so
>> let's use the same quirk to handle that.
>>
>> Signed-off-by: Maximilian Luz <luzmaximilian@...il.com>
>> ---
>>
>> For what it's worth, I don't think the ACPI spec explicitly states that
>> any of the status bits need to be set, or that there are only the
>> "charging" and "discharging" states. As far as I can tell, ACPI only
>> states:
>>
>>      Notice that the Charging bit and the Discharging bit are mutually
>>      exclusive and must not both be set at the same time. Even in
>>      critical state, hardware should report the corresponding
>>      charging/discharging state.
>>
>> But that does not exclude the case that no bit is set. So, strictly
>> going by spec, I don't think it's necessary to put all of this behind a
>> quirk.
> 
> I think that this should be covered by the patch I've just applied:
> 
> https://patchwork.kernel.org/project/linux-acpi/patch/20220427154053.499203-1-wse@tuxedocomputers.com/
> 
> Shouldn't it?

It does, thank you!

Sorry for having missed that one.

Regards,
Max