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README.md

PreSonus Quantum 2626 — Linux driver (skeleton)

Out-of-tree ALSA PCI driver skeleton for PreSonus Quantum 2626 (and family: 0101, 0102, 0103, 0105 from driver-reference/pae_quantum.inf). The card is registered and a PCM device appears. IRQ path is wired: the driver requests the device IRQ and calls snd_pcm_period_elapsed() from the interrupt handler for active playback/capture; if IRQ request fails, a timer fallback drives the pointer. No actual hardware I/O yet — no DMA or register programming; real playback/capture needs reverse engineering of pae_quantum.sys or the device BAR.

Base / references

  • Kernel: Writing an ALSA Driver (Takashi Iwai).
  • Structure: sound/pci/ens1370.c (Ensoniq AudioPCI) — PCI table, probe/remove, chip create, PCM registration.
  • IDs: driver-reference/pae_quantum.inf; Linux PCI baseline in notes/DIAGNOSIS_RESULT.md (1c67:0104, BAR 0 = 1 MiB).

What this driver does

  • PCI: Claims 1c67:0101, 0102, 0103, 0104, 0105.
  • Probe: Enables device, requests regions, maps BAR 0 with pci_iomap, logs the first 64 bytes of BAR 0 (MMIO+0x00..0x3c) to dmesg for reverse-engineering, tries MSI first (Thunderbolt often has legacy IRQ 0), then requests the device IRQ when valid (>0) with a shared handler that signals period elapsed for active substreams, creates ALSA card + one PCM (playback + capture), registers card.
  • Remove / free: Frees IRQ (if requested), frees MSI vectors (if allocated), unmaps BAR, releases regions, disables PCI.
  • PCM: Open/close/hw_params/hw_free/prepare/trigger/pointer; hardware descriptor allows common rates/channels so the device shows in aplay -l / arecord -l. Pointer is driven by IRQ (or timer fallback). No data is moved to/from hardware yet.

Build and load

cd driver
make
sudo insmod snd-quantum2626.ko

Or install and load via modprobe:

make install
sudo modprobe snd-quantum2626

For testing with debug output:

sudo insmod snd-quantum2626.ko dump_on_trigger=1

Quick status check:

../scripts/linux_test_driver.sh

Check:

aplay -l
arecord -l
cat /proc/asound/cards

Unload:

sudo rmmod snd-quantum2626

Optional: dump MMIO at prepare/trigger (for reverse-engineering)

Load with dump_on_trigger=1 to log the first 64 bytes of BAR 0 at each prepare and trigger START/STOP:

sudo modprobe snd-quantum2626 dump_on_trigger=1

Then run aplay or arecord; dmesg will show "MMIO at prepare", "MMIO at trigger START", "MMIO at trigger STOP". Compare with baseline (see docs/REVERSE_ENGINEERING_PLAN.md and scripts/probe_during_playback.sh).

Next steps (real audio)

  1. IRQ: Done. Handler runs and signals period elapsed; use dmesg to confirm IRQ is firing (or that timer fallback is used). Later: read a status register in the handler and only signal when the device actually reports a period (reverse-engineer BAR layout).
  2. PCM: Implement prepare/trigger/pointer to program the device’s DMA/buffers and report the real hardware pointer; use chip->iobase and the MMIO dump (dmesg after load) to infer register layout from pae_quantum.sys or experimentation.
  3. Format/channels: Adjust quantum_pcm_hw and constraints from device capabilities (e.g. 26 I/O from specs; may require multiple PCMs or channel maps).

Layout

  • snd-quantum2626.c — Single-file driver (PCI table, probe/remove, chip, stub PCM).
  • Makefile — Out-of-tree kernel build.
  • README.md — This file.