[OS Detection] Don't classify MacOS sequences as Windows when cnt_02 >= 2#26303
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bin101 wants to merge 1 commit into
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[OS Detection] Don't classify MacOS sequences as Windows when cnt_02 >= 2#26303bin101 wants to merge 1 commit into
bin101 wants to merge 1 commit into
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macOS 26.x (ChibiOS) can send a late wLength=0x04 packet after the two 0xFF packets that already established OS_MACOS. The Windows check (cnt_ff >= 2 && cnt_04 >= 1) fired on this combination and overwrites the correct result. Real-world Windows sequences always start with 0xFF packets (cnt_02 = 0); macOS sequences always open with at least two 0x02 packets (cnt_02 >= 2). Adding && setups_data.cnt_02 < 2 to the Windows condition is sufficient to separate the two populations without affecting any existing detection. Adds a regression test for the affected sequence.
bin101
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drashna
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Jun 30, 2026
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@drashna How many reviews are required for a merge? |
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Usually 2 approvals before a merge. Also, this should probably target the develop branch, rather than master. |
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Fixes macOS 26.x being misidentified as Windows on ChibiOS keyboards
Description
On macOS 26.x with ChibiOS-based keyboards, the USB enumeration sends a late wLength=0x04 packet after the two 0xFF packets that already correctly established OS_MACOS. The existing Windows detection condition (cnt_ff >= 2 && cnt_04 >= 1) fires on this combination and permanently overwrites the correct result, causing the keyboard to report OS_WINDOWS on macOS for the remainder of the session.
Observed sequence (ChibiOS, macOS 15.x):
[0x02, 0x22, 0x02, 0x0E, 0x02, 0x42, 0xFF, 0xFF, 0x04, 0xFF]
After packet #6 (0xFF), detected_os is correctly set to OS_MACOS (cnt_02=3, cnt_ff=1). At packet #8 (0x04), cnt_ff=2 and cnt_04=1 satisfy the Windows condition, overwriting OS_MACOS with OS_WINDOWS. The final 0xFF at packet #9 re-evaluates to OS_WINDOWS again. The debounced callback delivers the incorrect result.
Fix: Add setups_data.cnt_02 < 2 as a conjunct to the Windows detection condition. This is sufficient because:
These populations do not overlap. All existing Windows sequences in the test suite pass the new condition unchanged (cnt_02 = 0 in all cases).
A test case for the affected sequence has been added to
quantum/os_detection/tests/os_detection.cppTypes of Changes
Issues Fixed or Closed by This PR
Checklist