trackfile.device and DAControl

trackfile.device is an AmigaOS 3.2 device driver that presents ADF floppy-disk images as virtual floppy disks. Its companion CLI command, DAControl, inserts and ejects those images under script control. Together they let the OS 3.2 installer use a single installation script regardless of source medium (CD-ROM, hard disk, real floppies) by treating every source as a sequence of swappable virtual floppies.

NDK 3.2 R4 ships the full SAS/C 6 source for both in DAControl+trackfile/ — a rare, fully-documented device driver that emulates trackdisk.device as closely as possible.

Why it exists

The OS 3.2 team decided to use one installation script for every install medium. The lowest common denominator was "virtual floppy disks" that the script can insert and remove on demand. That virtual floppy drive is trackfile.device; the command driving it is DAControl. As the source README puts it: "Small as it may seem, the trackfile.device cuts a swath through the AmigaOS stack."

What trackfile.device does

It is a device driver that:

  • Accepts the standard trackdisk.device command set (CMD_READ, CMD_WRITE, CMD_UPDATE, TD_* geometry/query commands), so existing floppy-aware software works unmodified.
  • Backs each unit with an ADF disk-image file rather than physical media.
  • Caches tracks and performs MFM encode/decode to emulate the floppy bitstream faithfully.
  • Swaps its own stack (device calls may execute on the caller's stack) via swap_stack.asm.

The source is laid out to mirror a textbook device driver:

File Role
trackfile_device.{c,h} Device entry point, library/vector init
unit.{c,h} Per-unit management
commands.{c,h} Command dispatch (read/write/geometry)
cache.{c,h} Track caching
mfm_encoding.{c,h} MFM encode/decode
functions.{c,h}, tools.{c,h} Helpers
system_headers.{c,h} OS includes
swap_stack.asm Stack swapping
goodies/ Raw disk read/write & recovery tools

What DAControl does

DAControl is the CLI front-end that the installer script calls to manage media:

  • Insert an ADF image by path into a unit (insert_media_by_name).
  • Mount a floppy image file (mount_floppy_file).
  • Compute ADF checksums the same way trackfile.device does internally (DAChecksum), for verifying images.
  • Handle Workbench icons for the media (process_icons).

Why it matters as a learning resource

Device drivers that emulate a well-known specification and are documented to this degree are rare. trackfile.device is therefore valuable as:

Build requirements

Both components build with SAS/C 6 (smakefile targets sc/link). They are not host-buildable on modern systems without SAS/C or a compatible cross-toolchain.

See Also

Sources: Hyperion Entertainment / AmigaOS Team, NDK 3.2 R4 DAControl+trackfile/ source and README, 2022. Raw: raw/devices/trackfile-device.md Updated: 2026-08-04