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1993-05-16
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70 lines
SCF Edition #14
===============
This archive includes the following files:
- scf14.ipc IPatch file for SCF edition 14
- scf14.doc This file
Use Bob Santy's IPatch utility to apply the patch. You must use
the stock Tandy SCF manager, who's ident output is below:
Header for: SCF
Module size: $05E3 #1507
Module CRC: $F946CA (Good)
Hdr parity: $0E
Edition: $0D #13
Ty/La At/Rv: $D1 $81
File Man mod, 6809 obj, re-en, R/O
After the patch is applied, the patched SCF's ident output should
match the one below:
Header for: SCF
Module size: $06DA #1754
Module CRC: $B7E7CB (Good)
Hdr parity: $37
Edition: $0E #14
Ty/La At/Rv: $D1 $82
File Man mod, 6809 obj, re-en, R/O
WHAT IS SCF EDITION 14?
SCF #14 adds Kevin Darling's popular SCF patches and (drum roll)
the ability for a device to be non-sharable.
"Necessity is the mother of invention." How true... and this
is something people have been needing for quite a while.
HOW TO MAKE A DEVICE NON-SHARABLE
To make a device non-sharable, add $40 to the byte at offset $0D in
both your device descriptor and its device driver. Only one path can
be opened at a time to a non-sharable device, and any attempt to
open another will result in an ERROR #250 (Device Busy)
WHAT MAKES IT TICK
Within each device's static storage, there is a head pointer to
a linked list of path descriptors. When SCF #14 is called by IOMAN
to open a path to a device, it checks this linked list to see if
it is empty. If it is, then it goes ahead and attempts to open
the path.
If the list is not empty (meaning that there is already a path open
to this device), SCF checks the M$Mode on both the driver and the
descriptor to see if the 6th bit is set (sharable bit). If it is set,
SCF returns ERROR #250, otherwise it adds the new path descriptor
to the linked list.
Enjoy!
Boisy G. Pitre - 5/15/93