Fix libusb_bulk_transfer timeout on some Android devices#19
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josephnef merged 2 commits intoMar 24, 2026
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…host fix (#314) Some MediaTek Android xhci/usbfs stacks (Dimensity 810, Helio G99, MT6765) never complete a bulk-IN read larger than 16 KB — LIBUSB_ERROR_TIMEOUT forever, zero RX with a green init (OpenIPC/PixelPilot#6). floppyhammer's #19 fixed this with 16 KB host reads plus ≤16 KB device-side RX aggregation; the async-ring rewrites (#158/#164/#168) and the #213 transport split (40e3a2a) kept the aggregation half but regressed the host reads to 32 KB URBs on every 11ac generation. PixelPilot#104 shipped the first Android build of the async ring and the no-video reports came straight back. - Jaguar1/2/3 RX rings: 16 KB URBs (DeviceConfig::Rx::urb_bytes, env DEVOURER_RX_URB_BYTES, clamped >= 4096). Free on healthy hosts: with aggregates capped ≤16 KB a 32 KB URB never filled past 16 KB anyway — each aggregate ends its URB via short packet. - Jaguar2/3 halmac agg page-threshold 0x05 (20 KB) -> 0x03 (≤12 KB): an aggregate must never span two URBs or the next_offset walk breaks. Deliberate divergence from the kernel's 0x05, documented at both sites. - Kestrel untouched: the 8852C RXAGG LEN_TH (~20 KB) requires its 32 KB ring; the knob is documented as 11ac-only. - Docs: CLAUDE.md hardware gotcha + performance-tuning.md lever entry. ctest 36/36. Desktop bench (regress 2x2, goodput A/B) and on-device MTK validation via PixelPilot#6 volunteers tracked in #314. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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…host fix (#314) Some MediaTek Android xhci/usbfs stacks (Dimensity 810, Helio G99, MT6765) never complete a bulk-IN read larger than 16 KB — LIBUSB_ERROR_TIMEOUT forever, zero RX with a green init (OpenIPC/PixelPilot#6). floppyhammer's #19 fixed this with 16 KB host reads plus ≤16 KB device-side RX aggregation; the async-ring rewrites (#158/#164/#168) and the #213 transport split (40e3a2a) kept the aggregation half but regressed the host reads to 32 KB URBs on every 11ac generation. PixelPilot#104 shipped the first Android build of the async ring and the no-video reports came straight back. - Jaguar1/2/3 RX rings: 16 KB URBs (DeviceConfig::Rx::urb_bytes, env DEVOURER_RX_URB_BYTES, clamped >= 4096). Free on healthy hosts: with aggregates capped ≤16 KB a 32 KB URB never filled past 16 KB anyway — each aggregate ends its URB via short packet. - Jaguar2/3 halmac agg page-threshold 0x05 (20 KB) -> 0x03 (≤12 KB): an aggregate must never span two URBs or the next_offset walk breaks. Deliberate divergence from the kernel's 0x05, documented at both sites. - Kestrel untouched: the 8852C RXAGG LEN_TH (~20 KB) requires its 32 KB ring; the knob is documented as 11ac-only. - Docs: CLAUDE.md hardware gotcha + performance-tuning.md lever entry. ctest 36/36. Desktop bench (regress 2x2, goodput A/B) and on-device MTK validation via PixelPilot#6 volunteers tracked in #314. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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…host fix (#317) Closes #314. ## What Restores the host-side half of @floppyhammer's MediaTek no-video fix (#19), lost when the RX path moved to the async URB ring and the #213 transport split deleted `RtlUsbAdapter.cpp`: - **Jaguar1/2/3 RX rings: 16 KB URBs** (was 32 KB), via new `DeviceConfig::Rx::urb_bytes` (env `DEVOURER_RX_URB_BYTES`, clamped ≥ 4096). - **Jaguar2/3 halmac agg page-threshold `0x05` → `0x03`** (20 KB → ≤12 KB): an aggregate must never span two URBs or the `next_offset` walk breaks. Deliberate divergence from the kernel's value, documented at both sites. - **Kestrel untouched**: the 8852C RXAGG LEN_TH (~20 KB) requires its 32 KB ring; the knob is documented 11ac-only. - Docs: `CLAUDE.md` hardware gotcha + `docs/performance-tuning.md` lever entry. ## Why it's free on healthy hosts The device-side aggregation caps (Jaguar1 `rxagg_usb_size` 0x3/0x1 — the surviving half of #19) mean every aggregate is ≤16 KB and ends its URB via short packet: a 32 KB URB never filled past 16 KB. The URB size change costs nothing; it only removes the shape MediaTek hosts can't complete. ## The regression chain 1. PixelPilot#6 (Sept 2024): no video on MTK devices; `libusb_bulk_transfer` → `LIBUSB_ERROR_TIMEOUT` forever ([diagnosis](OpenIPC/PixelPilot#6 (comment)) by @floppyhammer, Jan 2025). 2. #19 (`bbc7385`, Mar 2026): 16 KB reads + ≤16 KB aggregation. Validated on-device by two reporters. PixelPilot#97 pins it. 3. #158/#164/#168 async ring + #213 split (`40e3a2a`): aggregation half survives, host reads regress to 32 KB. 4. PixelPilot#104 (Jul 13): first Android build of the async ring. Jul 19: no-video reports return on the same devices. ## Validation - [x] ctest 36/36 green (Linux, system toolchain) - [x] Desktop bench: `tests/regress.py` matrices + delivery A/B 32K-vs-16K URBs — parity on J1/J2/J3 (table below) - [ ] On-device MTK: PixelPilot test APK to the #6 volunteers (Dimensity 810 + MT6765), plus one Snapdragon no-regression check 🤖 Generated with [Claude Code](https://claude.com/claude-code) ## Bench results (2026-07-20, local rig) Delivery A/B, devourer-RX cells, 15 s flood cells (`tests/regress.py`, `DEVOURER_RX_URB_BYTES` control arm): | RX chip (gen) | TX | ch | 16 KB URBs | 32 KB URBs | 16 KB repeat | |---|---|---|---|---|---| | RTL8812AU (J1) | 8821AU devourer flood | 6 | 7400/8000 | 7400/8000 | 7200/8000 | | RTL8812AU (J1) | 8821AU kernel | 6 | 300/327 | 300/333 | 300/324 | | RTL8812BU (J2, agg 0x03) | 8812AU devourer flood | 36 | 8400/8500 | 8400/8500 | — | | RTL8812EU (J3, agg 0x03) | 8812AU devourer flood | 36 | 8200/8500 | 8200/8500 | — | | RTL8812EU (J3, agg 0x03) | 8812AU kernel | 36 | 300/315 | 300/320 | — | Drift between arms matches the kernel-RX control cells (7217→7401→7355) — the URB size is invisible on healthy hosts, as predicted: with ≤16 KB aggregates each aggregate ends its URB via short packet, so a 32 KB buffer never filled past 16 KB. The J2/J3 agg `0x05→0x03` change shows no delivery cost (98.8% / 96.5% flood delivery, in line with this rig's history). Full 2×2 kernel-driver matrices pass on J1/J2 (ch 6 + ch 36); the J3 kernel cells are structurally absent (no kernel driver for the EU on this host). No 8814AU on the rig today — its delta is nil by construction (DMA-agg is 2 KB, far under either URB size; the multi-URB pool is untouched). Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>
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Fixes OpenIPC/PixelPilot#6.