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fix(ncm): wNdbInDivisor/wNdbOutDivisor rejected as 1 by Windows KB5124008 - #86
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@peter-marcisovsky This PR fixes NCM network cards with latest Windows. I'd like to release version 0.21.0.2 after it is merged, PTAL! |
peter-marcisovsky
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Sep 16, 2026
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A Windows Update (KB5124008, Sept 2026) enabled a feature-flag-gated NTB
parameter validation in usbncm.sys requiring wNdbOutDivisor (and by
symmetry wNdbInDivisor) to be >=4 and a power of 2. TinyUSB's NCM class
driver hardcodes both to 1 — spec-legal per NCM1.0, but now rejected,
causing STATUS_DEVICE_HARDWARE_ERROR (Code 10) in Device Manager before
the device gets past SelectConfiguration().
Root-caused via WinDbg kernel debugging (KDNET) cross-referenced against
Microsoft's own published NCM host driver reference source
(microsoft/NCM-Driver-for-Windows). Confirmed fixed on real hardware
(RP2040, Windows 11 post-KB5124008; also verified no regression on
Android).
4 is spec-legal on the device side and is the value most other NCM
devices already ship with, so this shouldn't affect any other host.
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