Re: [PATCH 0/3] power: supply: max17040: report charging status from a gpio-charger

[Hugo Karlsson]

Adding the other MAX17040 reviewers, LKML, and Svyatoslav as the
author of the commit in the Fixes: tag, whom I missed when sending.
Sorry for the noise.

//Hugo

On 08/11/2026 15:45, Hugo Karlsson wrote:
> Hi,
>
> I work on OpenFlight [1], an open-source golf launch monitor built on a
> Raspberry Pi 5 with a Geekworm X1202 UPS board. The board pairs a
> MAX1704x fuel gauge at I2C address 0x36 with a GPIO that is high while
> input power is present.
>
> With the gauge and a gpio-charger described in DT and linked by
> power-supplies, the battery still always reports status "Unknown", and
> capacity reads above 100 when the cell is full (103 here). Desktop
> battery indicators then show the wrong state, so we have been shipping
> a patched taskbar plugin to work around it.
>
> Patch 1 passes the device fwnode to the power supply core. Without it,
> power-supplies is never parsed, so the supplier status lookup added in
> commit f4b782af61ae never finds a supplier.
>
> Patch 2 covers suppliers that only report "online", such as a
> gpio-charger without a charge-status GPIO: the status is derived from
> power_supply_am_i_supplied(), and the battery now sends a change event
> when its supplier changes.
>
> Patch 3 clamps the reported capacity to 100.
>
> The series is based on for-next. I tested it on a Raspberry Pi 5 with an
> X1202, on rpi-6.18.y (6.18.50), where max17040_battery.c only differs
> in the style of the i2c_device_id table:
>
>    stock driver:          status Unknown, capacity 103
>    on mains at 100 %:     Full, capacity 100
>    unplugged:             Discharging
>    plugged in at 98 %:    Charging
>
> The battery's uevent follows the charger's within 1 ms.
>
> Related changes for the same boards, for context:
>    - Raspberry Pi overlay that links the gauge to the charger [2]
>    - Raspberry Pi OS taskbar battery plugin reading capacity [3]
>
> The patches and changelogs were written with Claude Code
> (claude-opus-5-5) from my description of the problem. I reviewed them
> and did the hardware testing above.
>
> [1] https://github.com/open-flight/openflight
> [2] https://github.com/raspberrypi/linux/pull/7744
> [3] https://github.com/raspberrypi-ui/pplug-batt/pull/17
>
> Thanks,
> Hugo
>
> Hugo Karlsson (3):
>    power: supply: max17040: pass the device fwnode to the power supply
>      core
>    power: supply: max17040: derive status from an online supplier
>    power: supply: max17040: clamp the reported capacity to 100 %
>
>   drivers/power/supply/max17040_battery.c | 28 +++++++++++++++++++++++--
>   1 file changed, 26 insertions(+), 2 deletions(-)