mtools: Porting mtools
6 Porting mtools to architectures which are not supported yet
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This chapter is only interesting for those who want to port mtools to
an architecture which is not yet supported. For most common systems,
default drives are already defined. If you want to add default drives
for a still unsupported system, run configuration.guess, to see which
identification autoconf uses for that system. This identification is of
the form cpu-vendor-os (for example sparc-sun-sunos). The cpu and the
OS parts are passed to the compiler as preprocessor flags. The OS
part is passed to the compiler in three forms.
1. The complete OS name, with dots replaced by underscores. SCO3.2v2
would yield sco3_2v2
2. The base OS name. SCO3.2v2 would yield Sco
3. The base OS name plus its major version. SCO3.2v2 would yield Sco3
All three versions are passed, if they are different.
To define the devices, use the entries for the systems that are
already present as templates. In general, they have the following form:
#if (defined (my_cpu) && defined(my_os))
#define predefined_devices
struct device devices[] = {
{ "/dev/first_drive", 'drive_letter', drive_description},
...
{ "/dev/last_drive", 'drive_letter', drive_description}
}
#define INIT_NOOP
#endif
"/dev/first_drive" is the name of the device or image file
representing the drive. Drive_letter is a letter ranging from a to z
giving access to the drive. Drive_description describes the type of the
drive:
`ED312'
extra density (2.88M) 3 1/2 disk
`HD312'
high density 3 1/2 disk
`DD312'
double density 3 1/2 disk
`HD514'
high density 5 1/4 disk
`DD514'
double density 5 1/4 disk
`DDsmall'
8 sector double density 5 1/4 disk
`SS514'
single sided double density 5 1/4 disk
`SSsmall'
single sided 8 sector double density 5 1/4 disk
`GENFD'
generic floppy drive (12 bit FAT)
`GENHD'
generic hard disk (16 bit FAT)
`GEN'
generic device (all parameters match)
`ZIPJAZ(flags)'
generic ZIP drive using normal access. This uses partition 4.
`Flags' are any special flags to be passed to open.
`RZIPJAZ(flags)'
generic ZIP drive using raw SCSI access. This uses partition 4.
`Flags' are any special flags to be passed to open.
`REMOTE'
the remote drive used for floppyd. Unlike the other items, this
macro also includes the file name ($DISPLAY) and the drive letter
(X)
Entries may be described in more detail:
fat_bits,open_flags,cylinders,heads,sectors,DEF_ARG
or, if you need to describe an offset (file system doesn't start at
beginning of file system)
fat_bits, open_flags, cylinders, heads, sectors, offset, DEF_ARG0
`fat_bits'
is either 12, 16 or 0. 0 means that the device accepts both types
of FAT.
`open_flags'
may include flags such as O_NDELAY, or O_RDONLY, which might be
necessary to open the device. 0 means no special flags are needed.
`cylinders,heads,sectors'
describe the geometry of the disk. If cylinders is 0, the heads
and sectors parameters are ignored, and the drive accepts any
geometry.
`offset'
is used if the DOS file system doesn't begin at the start of the
device or image file. This is mostly useful for Atari Ram disks
(which contain their device driver at the beginning of the file)
or for DOS emulator images (which may represent a partitioned
device.
Definition of defaults in the devices file should only be done if
these same devices are found on a large number of hosts of this type.
In that case, could you also let me know about your new definitions, so
that I can include them into the next release. For purely local file, I
recommend that you use the `/etc/mtools.conf' and `~/.mtoolsrc'
configuration files.
However, the devices files also allows to supply geometry setting
routines. These are necessary if you want to access high capacity disks.
Two routines should be supplied:
1. Reading the current parameters
static inline int get_parameters(int fd, struct generic_floppy_struct *floppy)
This probes the current configured geometry, and return it in the
structure generic_floppy_struct (which must also be declared).
Fd is an open file descriptor for the device, and buf is an already
filled in stat structure, which may be useful. This routine
should return 1 if the probing fails, and 0 otherwise.
2. Setting new parameters
static inline int set_parameters(int fd, struct generic_floppy_struct *floppy)
struct stat *buf)
This configures the geometry contained in floppy on the file
descriptor fd. Buf is the result of a stat call (already filled
in). This should return 1 if the new geometry cannot be
configured, and 0 otherwise.
A certain number of preprocessor macros should also be supplied:
`TRACKS(floppy)'
refers to the track field in the floppy structure
`HEADS(floppy)'
refers to the heads field in the floppy structure
`SECTORS(floppy)'
refers to the sectors per track field in the floppy structure
`SECTORS_PER_DISK(floppy)'
refers to the sectors per disk field in the floppy structure (if
applicable, otherwise leave undefined)
`BLOCK_MAJOR'
major number of the floppy device, when viewed as a block device
`CHAR_MAJOR'
major number of the floppy device, when viewed as a character
device (a.k.a. "raw" device, used for fsck) (leave this undefined,
if your OS doesn't have raw devices)
For the truly high capacity formats (XDF, 2m, etc), there is no clean
and documented interface yet.
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