Hi, you asked:
1. Does freeDOS have a ramdisk and if so how do I use it?
Yes. It works as a sector providing driver. When it is loaded,
the FAT drivers can use it as a simulated drive. It has no
"idea" of FAT, it just provides disk space. I personally prefer
using XMSDSK, but you can use TDSK (which has open source versions).
For your Solaris project, you should keep things simple. Trap the
disk access at highest possible sector level and translate "write
sector" into "write to (memory area, offset (512*sector number)"
directly. In Solaris, you will need no XMS or EMS memory drivers,
and I assume you will want only one ramdisk and no DOS anyway.
Which leads to the question: Why not use EXISTING FAT drivers and
EXISTING ramdisks in Solaris? There must be some. And after all,
FAT is not even particularily well suited for Unixish file storage.
2. What does execrh do?
It is a quite lowlevel part in the call chain used for disk accesses.
You do not want to port it to Solaris. You want to trap the access
higher (after execrh, the "disk driver" is called, which in turn
calls the BIOS to access the real disk, or calls other drivers to
access the memory which "is" the ramdisk, in the case of RAMDISK
"disk drivers").
You do not need buffers for a RAMDISK either.
What you want is to replace dskxfer() by your own function
which accesses the ramdisk or image file directly:
UWORD dskxfer(COUNT dsk, ULONG blkno, VOID FAR * buf, UWORD numblocks,
COUNT mode)
dsk is the drive number, blkno the sector number, buf a buffer,
numblocks the number of sectors to access, and mode can be one of
DSKWRITE (possibly with verify) or DSKREAD or the variants
DSKWRITEINT26 or DSKREADINT25.
3. Bart wrote:The default block device driver is in dsk.c...
You do not need all this for your ramdisk. I assume you will NOT
have partitions on the ramdisk, and I assume you will just use linear
("lba") sector numbers, not position descriptions in "sector head cylinder"
terms. If you cut the chain at dskxfer, you only have to deal with the
linear blkno and the drive number. No "drive geometry", no partitions.
Eric
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