DOS provides the interrupt 2f/12xx functions for use by
filesystem redirectors in order that they do not need to access
structures and variables using undocumented methods. Interrupt
2f/1217 is a function used by a redirector to get the CDS entry
corresponding to a drive without iterating the CDS array found
via SYSVARS LOL.
FreeDOS currently validates the flags in CDS entry before
deciding whether to return the entry to the caller. This behaviour
prevents a redirector receiving the CDS entry corresponding to
an as yet unassigned drive so preventing any new drive mapping.
I've tested the following flavours of DOS and only FreeDOS
does this.
# DOS variants returning new CDS entries okay
DR-DOS
6.00-930319 7.00 7.01 7.02-971119 7.02-980123 7.03 8.00
MS-DOS
3.10 3.20 3.21 3.30-Nec 3.30 3.31 4.01 5.00 6.00 6.20 6.21 6.22
7.00 7.10
PC-DOS
3.00-Compaq 3.00 3.10-850307 3.10-850422 3.10-Compaq 3.20-851230
3.20-860221 3.30 3.31-Compaq 4.00 4.01 5.00 5.02 6.10 6.30 7.00
7.10 7.2K
# DOS variants that return error rather than new CDS entry
FR-DOS
1.00 1.10 1.20
This patch introduces an unvalidated version of get_cds() and calls
it only for the int2f/1217h call, other uses remain as before.
