Battery percentage not shown for devices using kernel HID driver (PS4/PS5 controllers)

[jamerrq]

Some Bluetooth devices (notably PS4/PS5 DualShock/DualSense controllers) report their
battery level through the kernel HID driver instead of the Bluetooth Battery Service (BAS)
profile. This means BlueZ does not expose the org.bluez.Battery1 D-Bus interface for
these devices, and bluetui shows no battery percentage even though the information is
available.

Steps to Reproduce

1. Connect a PS4 DualShock 4 controller via Bluetooth
2. Verify battery is reported by the kernel:
   $ cat /sys/class/power_supply/ps-controller-battery-XX:XX:XX:XX:XX:XX/capacity 75
3. Verify BlueZ does NOT expose Battery1:

$ dbus-send --system --dest=org.bluez --print-reply

/org/bluez/hci0/dev_XX_XX_XX_XX_XX_XX

org.freedesktop.DBus.Properties.GetAll string:"org.bluez.Battery1" Error

org.freedesktop.DBus.Error.InvalidArgs: No such interface 'org.bluez.Battery1'

4. Open bluetui — no Battery column is shown

Expected Behavior

The battery percentage should be displayed for these devices.

Proposed Solution

Add a fallback that reads from /sys/class/power_supply/ when bluer returns None
for battery_percentage(). The fallback matches device entries by MAC address in the
sysfs directory name and reads the capacity file.
This is a ~20-line change in bluetooth.rs, synchronous, with no new dependencies.

Environment

• OS: Arch Linux
• Kernel: Linux 6.19.10-arch1-1
• BlueZ: 5.85
• bluetui: 0.8.1
• Device: Sony DualShock 4 (CUH-ZCT2U)

[sermuns]

Thanks for the thorough explanation, I will take a look at this later this week!

[jamerrq]

I just submitted #137 with the suggested change I explained here, take a look it could be useful for this

[sermuns]

I've tried connecting a Nintendo Switch Pro Controller where this same problem occurs.

However, it seems the Pro Controller doesn't expose a capacity, just a rough estimate in the form of capacity_level which can be unknown, critical, low, normal, high or full ¹.

$ cat /sys/class/power_supply/nintendo_switch_controller_battery_0005\:057E\:2009.0014/capacity_level 
Normal

I wonder if we should support this too, and if the pretty thing to do is to "lie" to the user by converting this capacity_level to hardcoded percentages. For instance normal->50%, full->100%, e.g..

Footnotes

1. https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/include/linux/power_supply.h?h=v6.19#n88 ↩

[jamerrq]

I think supporting capacity_level as a secondary fallback makes sense — it would cover the Switch Pro Controller and likely other HID devices in the same situation.

Regarding the percentage mapping: I'd say it's reasonable since the UI already displays battery in ranges with icons (90+, 80-90, etc.), so an approximate value still maps to the correct icon. The alternative would be showing the raw level as text (e.g. "Normal") but that would require changing battery_percentage from Option<u8> to something more complex and touching the rendering logic.

At #137 I've added capacity_level as a secondary fallback: capacity is tried first (exact %), then capacity_level with the mapping Full→100, High→75, Normal→50, Low→25, Critical→5. Lmk what you think.