ric@mcrware.UUCP (Ric Yeates) (03/07/91)
Netlanders:
I need to write some software to add partitions to the partition table
stored on sector 0 of a hard disk. I will be adding partitions for the
areas that are not yet used on the disk. For instance, Joe User has a
80Meg drive and sets up two 30Meg partitions with HDX.PRG. My program
wants to then go in there (at the request of the user) and add a partition
or two in the unused 20Meg of space. These are not to be GEM partitions, but
they should conform as far as the partition table information is concerned.
What I've been able to figure out so far is:
* the partition table starts at 0x1c7
* the table entries are in the following form:
struct part_entry {
char name[3];
long start; /* 32-bit sector number */
long length; /* 32-bit length in sectors */
char flag; /* 1 byte flag where 0x01 means bootable */
};
* offset 0x1c2 is the start of a 32-bit value for the total number of
sectors on the device
My questions are:
1. Is any of the above information inaccurate? Incomplete?
2. What is the significance of the byte at 0x1c6 (sandwiched between the
total sectors and the partition table)? On my drive it has the value
0x81 (%10000001).
3. Is there other information in this sector that I will need to write a
partitioner?
4. Is there a checksum/parity value kept for sector 0? How does HDX3.01 know
it was used to format the hard disk?
5. How might an application read sector 0? All the GEMDOS calls I found
dealt with files only, not the whole device.
6. Are there any decent/recent books on this sort of thing?
I suppose that's enough for now.
Thanks in advance for any help that you may be able to provide.
Ric Yeates
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
Ric Yeates Microware Systems Corp.
"I found these opinions on the floor, so I don't think they belong
to Microware."
1. Grease Generously
2. Wax Philosophically
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=bjoern@drdhh.hanse.de (Bjoern Kriews) (03/13/91)
From article <5208@mcrware.UUCP>, by ric@mcrware.UUCP (Ric Yeates): > I need to write some software to add partitions to the partition table > stored on sector 0 of a hard disk. > * the table entries are in the following form: > struct part_entry { WRONG !!! flag has to be here, bit 7 means bootable > char name[3]; > long start; /* 32-bit sector number */ > long length; /* 32-bit length in sectors */ > char flag; /* 1 byte flag where 0x01 means bootable */ > }; > 1. Is any of the above information inaccurate? Incomplete? Yes. :-) More questions answered below. > 5. How might an application read sector 0? All the GEMDOS calls I found > dealt with files only, not the whole device. If you detect an AHDI or compatible driver, you can set bit 3 in the Rwabs() mode-word to read physical sectors, but to be safe you will have to use direct DMA access. (Ask your Microware devdrvr writers) In germany, there's a VERY good book, called 'Scheibenkleister', published by Maxon. It's about all mass-storage devices on the ST. I don't think that there is an english version, so you'll have to search somebody reading ger-mish - it worth the action. I include the C definitions I use for such tools: (ICD/Supra Rootsectors only - there are official docs from Atari describing HDX 3.0 Format, but they are (c), so you have to ask Atari. Hope that helps, Bjoern --------- #define PART_EXIST 1 #define PART_BOOT 128 /* partition definition */ struct part { unsigned char flag; /* bit 0: exists bit 7: boot */ unsigned char id[3]; /* partition name */ unsigned long start; /* start sector */ unsigned long size; /* size in sectors */ }; /* rootsector structure */ typedef struct { unsigned char prg[0x150]; /* bootprogram */ unsigned char version; /* rootsector version number */ unsigned long cbhd; /* Driver magic longword */ struct part extp[8]; /* extended parts SED/ICD/Supra */ unsigned int hi_cc; /* cylinders on disk */ unsigned char hi_dhc; /* number of heads */ unsigned char filler; /* unused */ unsigned int hi_rwcc; /* reduced current start */ unsigned int hi_wpc; /* write precomp start */ unsigned char hi_lz; /* landing zone distance */ unsigned char hi_rt; /* steprate */ unsigned char hi_in; /* interleave */ unsigned char hi_spt; /* sectors per track */ unsigned long hi_size; /* total size in sectors */ struct part p[4]; /* atari hdx<3.0 partitions */ unsigned long bsl_start; /* bad sector list start */ unsigned long bsl_count; /* number of sectors in bsl */ unsigned int checksum; /* fixup for $1234 */ } ROOTBLK; * * bjoern@drdhh.hanse.de / Bjoern Kriews, D-2000 Hamburg 76 *
apratt@atari.UUCP (Allan Pratt) (03/22/91)
Somebody asks: >>[How do I read device sector 0?] bjoern@drdhh.hanse.de (Bjoern Kriews) writes: >If you detect an AHDI or compatible driver, you can set bit 3 in the >Rwabs() mode-word to read physical sectors, but to be safe you will >have to use direct DMA access. (Ask your Microware devdrvr writers) Yikes! Do I really have to go into the dangers of this kind of thinking? NEVER use direct DMA access. You are SURE to get it wrong and screw up something. Who has drivers which DON'T support the raw-device bit? Whoever they are, their drivers are not complete, at least as defined by Atari's documentation of the Rwabs() call. ============================================ Opinions expressed above do not necessarily -- Allan Pratt, Atari Corp. reflect those of Atari Corp. or anyone else. ...ames!atari!apratt