mt7925: status LED of USB adapters and linux-firmware

[Josef Schlehofer]

Hi,

The status LED of MT7925 USB adapters stays off on Linux. I
investigated this with a NETGEAR A9000 (0846:9072), see [1].

MediaTek's Windows driver for the A9000 (mtkwecxu.sys 5.3.0.3230)
controls the LED using UNI command 0x2a, with GPIO 8 and a TLV (tag 1)
specifying the LED state (on/off). Sending the same command from mt76
works with the firmware from the Windows driver package
(MT7925_E1_ASIC_ROM_RAM_CE_2249_CCN10_USB, 20250424), but not with
linux-firmware builds (CE_2249_CCN16, tested with 20231227 and
20260813). The latter return status 0 but do not change the LED state.
All 16 MT7925 firmware releases currently in linux-firmware are CCN16
builds.

Could you clarify:

1. Can GPIO-based LED control be enabled in the linux-firmware build
   for MT7925 USB adapters?

2. If not, what is the intended way to control these LEDs on Linux?

3. Is GPIO 8 common to all MT7925 USB adapters, or is it
   board-specific?

I have a small mt76 patch that registers the LED for MT7925 USB devices
and sends this command. I will submit it once firmware support and GPIO
selection are clarified.

[1] https://github.com/morrownr/USB-WiFi/issues/731

Thanks,
Josef