HP ScanJet 8250 Duplex broken (avision backend)
Scanning in ADF duplex mode is broken in current HEAD (cfbc7448) and probably since b82e9949.
When scanning, the ADF feeds the page correctly and the front and back of the first page are scanned while STDOUT says it's scanning page one (there seems to be a hacky implementation where the second page is written to a temp file and then reread from that file when the lib asks for the second page?). Then the scanimage app dies because "rear_fp" is 0.
The problem seems to be related to avision.c:6834 as it only initializes the rear_fp variable when !(s->page % 2), which is clearly wrong, because the file needs to be alternately read and written so it always needs to be initialized.
Tracking down changes to that IF statement I found b82e9949 which seems to be related to this bug.
In b82e9949^ (104b43a1) scanning in ADF duplex mode works, but the format detection is broken and every page is elongated.
Attached: full debug.log, core.22387