Лично я спокойно использую стандартные драйвера для чтения qnx4 партиции созданной под QNX6.x.
AFAIK qnx4_filesystem for qnx4 не сильно отличается от таковой в qnx6.x : http://www.qnx.com/developers/docs/momentics621_docs/neutrin...
http://www.qnx.com/developers/docs/momentics621_docs/neutrin...The QNX4 filesystem (fs-qnx4.so) is a high-performance filesystem that shares the same on-disk structure as QNX 4.
The QNX4 filesystem implements an extremely robust design, utilizing an extent-based, bitmap allocation scheme with fingerprint control structures to safeguard against data loss and to provide easy recovery. Features include:
* extent-based POSIX filesystem
* robustness: all sensitive filesystem info is written through to disk
* on-disk "signatures" and special key information to allow fast data recovery in the event of disk damage
* 505-character filenames
* multi-threaded design
* client-driven priority
* same disk format as the filesystem under QNX 4.
Since the release of 6.2.1, the 48-character filename limit has increased to 505 characters via a backwards-compatible extension. The same on-disk format is retained, but new systems will see the longer name, old ones will see a truncated 48-character name.
For more information, see the technical note "The QNX4 Filesystem" in the Technotes section in the QNX Neutrino online docset.