Re: [PATCH v3 0/2] Add support for Battery Status AMS

[Sebastian Reichel]

Hi,

On Tue, Jun 02, 2026 at 10:47:05PM +0000, Amit Sunil Dhamne via B4 Relay wrote:
> PD 3.1 v1.8 Spec necessitates a response to Get_Battery_Status request
> from the port partner (see "6.13.2 Applicability of Data Message").
> This patchset adds support to get all the battery type power supplies
> and query them to report the telemetry required to build a Battery
> Status Message. Right now, this submission assumes all the battery type
> power supplies that exist in the system are fixed (meaning cannot be hot
> swapped).
> 
> Previously, I had sent a patch series [1]. However there were some
> concerns. Broadly:
>   * No client drivers
>   * Duplicating dt properties
> To address the above issues, we now have Fuel Gauge and Charger drivers.
> Also, I have rectified my approach to fetch information about batteries
> from the power supply core.
> 
> While, the original patch series [1] added support for Battery Caps as
> well, this patch series only adds support for Battery Status. Therefore,
> I am sending it as a new series while incorporating relevant feedback.
> 
> [1] https://lore.kernel.org/all/20250507-batt_ops-v2-0-8d06130bffe6@xxxxxxxxxx/
> 
> Patches in series:
> [A] "power: supply: Add helpers to get and put arrays of power supply handles"
> [B] "usb: typec: tcpm: Add support for Battery Status response message"
> 
> Technical dependency of patches:
> [B] depends on [A] due to usage of `power_supply_get_battery_all` &
> `power_supply_put_battery_all` APIs.
> 
> Signed-off-by: Amit Sunil Dhamne <amitsd@xxxxxxxxxx>
> ---

I think you want to filter on batteries that are
POWER_SUPPLY_SCOPE_SYSTEM? Otherwise this would also give you
battery devices for something like a cordless mouse.

You mention that this is assuming batteries to be always present,
but handle POWER_SUPPLY_PROP_PRESENT. So basically a battery, which
has POWER_SUPPLY_PROP_PRESENT=0 would violate the PD spec as Fixed
Batteries are not supposed to have this unset?

Not sure if this is fixable, but you implicitly rely on the battery
driver to be probed before TCPM reaches this.

Greetings,

-- Sebastian

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