XHDI Driver Specification
How to Extend An XHDI Driver
(which is what must be done when installing more than one
XHDI driver)
During the installation, check if the cookie is alreay set. If so:
- For XHGetVersion()?, first jump through the old vector and return the minimum of this and your own version number.
- For XHDrvmap(), first jump through the old vector and then add the the drive bits for the devices supported by your driver.
- For all other functions: check if the device is one of thoses supported by your driver. If not, jump through the old vector.
The 'RAW' Partition type
XHDI-1.10 compliant drivers shall support the third partition type
'RAW' (in addition to
'GEM' and
'BGM'). For these partitions, the following should be true:
- The partition size is "arbitrary" (32 bit sector numbers).
- The partition can be accessed as BIOS device; Getbpb() returns a NULL pointer (so that GEMDOS won't access it; however, calling Getbpb() resets the driver internal media change state).
- Rwabs() (in physical or logical mode) and XHReadWrite() may be used to access the partition. The physical block size of the medium is used (see XHInqTarget()?).
- XHInqDev2()? (as compared to XHInqDev()?) returns size and type of the partition.
These extensions have been made to make it easier to create drivers for new filesystems for
MiNT or
MagiC? (like the Minix file system).
Recommended partition types
| Partition Type |
Comment |
| 'BGM' |
GEMDOS partition > 16MB |
| 'GEM' |
GEMDOS partition < 16MB |
| 'RAW' |
see above |
The following types can be supported optionally (for example with a configurable list of partition ID's in the driver).
| Partition Type |
Comment |
| 'F32' |
TOS compatible FAT32 partition |
| 'LNX' |
Linux Ext2? partition, should be handled like 'RAW' |
| 'MAC' |
MAC HFS partition, should be handled like 'RAW' |
| 'MIX' |
Minix partition, should be handled like 'RAW' |
| 'QWA' |
QDOS partition, should be handled like 'RAW' |
| 'SWP' |
Swap partition, should be handled like 'RAW' |
| 'UNX' |
ASV (Atari System V) partition, should be handled like 'RAW' |
Arbitration
For device drivers which support SCSI arbitration, the machine needs an own SCSI device number which must be unique and shouldn't be stored on disk. Atari has reserved byte 16 in the Non Volatile Memory of the Atari TT and Falcon computers. Bit assignments:
| Bit |
Meaning |
| 0..2 |
device number |
| 7 |
arbitration on (1) or off (0) |
The current arbitration number could be inquired this way:
int
arbitration_id (void)
{
long ret = EINVFN;
unsigned char nvmdata = 0;
OSHEADER *Sys;
long oldstack = Super (0L);
Sys = *_sysbase;
Super ((void *)oldstack);
host_id = -1; /* no arbitration by default */
if (Sys->os_version >= 0x300)
ret = NVMaccess (0, 16, (int) sizeof (nvmdata), &nvmdata);
if (ret == E_OK && (nvmdata & 0x80))
host_id = nvmdata & 7;
return host_id;
}
See Also