don't reset printer when probing or releasing scanner, that kills any printing in progress
umax_pp command line tool has a bug which leads in producing
'shifted' scans sometimes
at 600 and 1200 dpi, the 32 bits I/O are sensitive to latency
issues. That may confuse the scanner, which needs then to be resetted.
To avoid this, don't load your system, or reduce the width of the scan.
Small width scans at high resolution are OK. Also using ECP only direct hardware
access alleviate this problem.
/dev/ppi0 on freebsd 5.x fails reading data from scanner in EPP mode, seems a freebsd bug.