When connecting my Steam controller, the battery fails to register and leaves a kernel backtrace in dmesg:

[85798.183418] hid-steam 0003:28DE:1142.0018: Steam Controller 'XXXXXXXXXX' connected
[85798.187918] hid-steam 0003:28DE:1142.0016: Steam Controller 'XXXXXXXXXX' connected
[85798.187959] sysfs: cannot create duplicate filename '/class/power_supply/steam-controller-XXXXXXXXXX-battery'
[85798.187964] CPU: 6 PID: 2070696 Comm: kworker/6:0 Tainted: P           O      5.10.25-gentoo #1
[85798.187965] Hardware name: To Be Filled By O.E.M. To Be Filled By O.E.M./Z68 Pro3, BIOS L2.16A 02/22/2013
[85798.187974] Workqueue: events steam_work_connect_cb [hid_steam]
[85798.187977] Call Trace:
[85798.187995]  dump_stack+0x58/0x6b
[85798.188006]  sysfs_warn_dup.cold+0x17/0x24
[85798.188017]  sysfs_do_create_link_sd+0xb9/0xc0
[85798.188022]  device_add+0x221/0x790
[85798.188030]  __power_supply_register+0x235/0x420
[85798.188034]  steam_register+0x31e/0x350 [hid_steam]
[85798.188038]  steam_work_connect_cb+0x36/0x50 [hid_steam]
[85798.188046]  process_one_work+0x1a8/0x2f0
[85798.188052]  worker_thread+0x48/0x3d0
[85798.188054]  ? rescuer_thread+0x390/0x390
[85798.188058]  kthread+0x126/0x150
[85798.188061]  ? kthread_create_worker_on_cpu+0x40/0x40
[85798.188064]  ret_from_fork+0x1f/0x30
[85798.188097] hid-steam 0003:28DE:1142.0016: steam_battery_register:power_supply_register failed with error -17
[85798.192799] hid-steam 0003:28DE:1142.0005: Steam Controller 'XXXXXXXXXX' connected
[85798.192841] sysfs: cannot create duplicate filename '/class/power_supply/steam-controller-XXXXXXXXXX-battery'
[85798.192847] CPU: 6 PID: 2070696 Comm: kworker/6:0 Tainted: P           O      5.10.25-gentoo #1
[85798.192849] Hardware name: To Be Filled By O.E.M. To Be Filled By O.E.M./Z68 Pro3, BIOS L2.16A 02/22/2013
[85798.192857] Workqueue: events steam_work_connect_cb [hid_steam]
[85798.192861] Call Trace:
[85798.192883]  dump_stack+0x58/0x6b
[85798.192896]  sysfs_warn_dup.cold+0x17/0x24
[85798.192907]  sysfs_do_create_link_sd+0xb9/0xc0
[85798.192917]  device_add+0x221/0x790
[85798.192926]  __power_supply_register+0x235/0x420
[85798.192932]  steam_register+0x31e/0x350 [hid_steam]
[85798.192935]  steam_work_connect_cb+0x36/0x50 [hid_steam]
[85798.192946]  process_one_work+0x1a8/0x2f0
[85798.192950]  worker_thread+0x48/0x3d0
[85798.192953]  ? rescuer_thread+0x390/0x390
[85798.192958]  kthread+0x126/0x150
[85798.192963]  ? kthread_create_worker_on_cpu+0x40/0x40
[85798.192967]  ret_from_fork+0x1f/0x30
[85798.193003] hid-steam 0003:28DE:1142.0005: steam_battery_register:power_supply_register failed with error -17
[85798.670552] hid-steam 0003:28DE:1142.0016: Steam Controller 'XXXXXXXXXX' disconnected
[85798.701106] hid-steam 0003:28DE:1142.0018: Steam Controller 'XXXXXXXXXX' disconnected
[85804.400855] input: Microsoft X-Box 360 pad as /devices/virtual/input/input30

Also, it seems to register the same battery name twice. I'm sure 'XXXXXXXXXX' is a placeholder that should be filled with some unique value.

I'm not sure if this is a Steam issue or comes from a kernel driver itself. In the latter case I'm not sure if Valve is responsible for the in-kernel driver, so I'm still reporting it here.