linux-kernel - Re: [PATCH v2 1/8] power: supply: core: Add resistance power supply property

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Message-ID: <e9160bb8-2b5c-4c30-b60f-520decde851e@oss.qualcomm.com>
Date: Mon, 30 Jun 2025 16:28:14 +0800
From: Fenglin Wu <fenglin.wu@....qualcomm.com>
To: Sebastian Reichel <sebastian.reichel@...labora.com>
Cc: Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>, Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley
 <conor+dt@...nel.org>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Subbaraman Narayanamurthy <subbaraman.narayanamurthy@....qualcomm.com>,
        David Collins <david.collins@....qualcomm.com>,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, kernel@....qualcomm.com,
        devicetree@...r.kernel.org, linux-usb@...r.kernel.org
Subject: Re: [PATCH v2 1/8] power: supply: core: Add resistance power supply
 property


On 6/22/2025 9:26 AM, Sebastian Reichel wrote:
> Hi,
>
> On Fri, May 30, 2025 at 03:35:06PM +0800, Fenglin Wu via B4 Relay wrote:
>> From: Fenglin Wu <fenglin.wu@....qualcomm.com>
>>
>> Some battery drivers provide the ability to export resistance as a
>> parameter. Add resistance power supply property for that purpose.
> This is missing some information and the naming is bad.
>
> Which resistance (I suppose battery internal resistance)?
>
> That is heavily dependent on the battery temperature. So this needs
> to document if this is for the current temperature or for some
> specific one.
>
> -- Sebastian

This is battery internal resistance calculated by battery management 
system, using the real-time temperature measured by the thermistor 
inside the battery pack.

I can update the name to something like "rt_internal_resistance" and 
update the description accordingly.

>> Signed-off-by: Fenglin Wu <fenglin.wu@....qualcomm.com>
>> ---
>>   Documentation/ABI/testing/sysfs-class-power | 10 ++++++++++
>>   drivers/power/supply/power_supply_sysfs.c   |  1 +
>>   include/linux/power_supply.h                |  1 +
>>   3 files changed, 12 insertions(+)
>>
>> diff --git a/Documentation/ABI/testing/sysfs-class-power b/Documentation/ABI/testing/sysfs-class-power
>> index 560124cc31770cde03bcdbbba0d85a5bd78b15a0..22a565a6a1c509461b8c483e12975295765121d6 100644
>> --- a/Documentation/ABI/testing/sysfs-class-power
>> +++ b/Documentation/ABI/testing/sysfs-class-power
>> @@ -552,6 +552,16 @@ Description:
>>   			Integer > 0: representing full cycles
>>   			Integer = 0: cycle_count info is not available
>>   
>> +What:		/sys/class/power_supply/<supply_name>/resistance
>> +Date:		May 2025
>> +Contact:	linux-arm-msm@...r.kernel.org
>> +Description:
>> +		Reports the resistance of the battery power supply.
>> +
>> +		Access: Read
>> +
>> +		Valid values: Represented in microohms
>> +
>>   **USB Properties**
>>   
>>   What:		/sys/class/power_supply/<supply_name>/input_current_limit
>> diff --git a/drivers/power/supply/power_supply_sysfs.c b/drivers/power/supply/power_supply_sysfs.c
>> index a438f7983d4f6a832e9d479184c7c35453e1757c..dd829148eb6fda5dcd7eab53fc70f99081763714 100644
>> --- a/drivers/power/supply/power_supply_sysfs.c
>> +++ b/drivers/power/supply/power_supply_sysfs.c
>> @@ -220,6 +220,7 @@ static struct power_supply_attr power_supply_attrs[] __ro_after_init = {
>>   	POWER_SUPPLY_ATTR(MANUFACTURE_YEAR),
>>   	POWER_SUPPLY_ATTR(MANUFACTURE_MONTH),
>>   	POWER_SUPPLY_ATTR(MANUFACTURE_DAY),
>> +	POWER_SUPPLY_ATTR(RESISTANCE),
>>   	/* Properties of type `const char *' */
>>   	POWER_SUPPLY_ATTR(MODEL_NAME),
>>   	POWER_SUPPLY_ATTR(MANUFACTURER),
>> diff --git a/include/linux/power_supply.h b/include/linux/power_supply.h
>> index c4cb854971f53a244ba7742a15ce7a5515da6199..de3e88810e322546470b21258913abc7707c86a7 100644
>> --- a/include/linux/power_supply.h
>> +++ b/include/linux/power_supply.h
>> @@ -174,6 +174,7 @@ enum power_supply_property {
>>   	POWER_SUPPLY_PROP_MANUFACTURE_YEAR,
>>   	POWER_SUPPLY_PROP_MANUFACTURE_MONTH,
>>   	POWER_SUPPLY_PROP_MANUFACTURE_DAY,
>> +	POWER_SUPPLY_PROP_RESISTANCE,
>>   	/* Properties of type `const char *' */
>>   	POWER_SUPPLY_PROP_MODEL_NAME,
>>   	POWER_SUPPLY_PROP_MANUFACTURER,
>>
>> -- 
>> 2.34.1
>>
>>