Path: utzoo!attcan!uunet!mcvax!unido!fauern!faui44!rtregn
From: rtregn@faui44.informatik.uni-erlangen.de (Robert Regn )
Newsgroups: comp.os.minix
Subject: Re: DOS[READ\WRITE\DIR] on hard disk
Message-ID: <342@faui10.informatik.uni-erlangen.de>
Date: 30 May 88 18:57:43 GMT
References: <2649@louie.udel.EDU>
Organization: CSD., University of Erlangen, W-Germany
Lines: 136
Posted: Mon May 30 19:57:43 1988

I've already tried to modify DOSxxx to handle hard disk's.
It uses the boot sector.  I made a link of /dev/hd<n> to /dev/at2,
so I need not remember which partition is dos.

The program - diff to 1.2 is included - works  (for 12 bit fats) ok as
dosdir and dosread, but as doswrite it destroys my dos partition (e.g.
root dir)!  Make a 100KB backup of the dos partition with dd if you
try doswrite.
I've put debug messages in "disk_io", but the behavior seems ok.
If i use doswrite on a file which contains a copy of the dos partitions
first MB, the program works! (Is the problem caused by the driver ??)

Can somebody send me the "mega-equation"  referenced by Marty ?
Can somebody say what hiddensec means ?

------------------------------ diff to dosread.c 1.2 ---------------
 20a21
 > #define HARDDISK	0xF8
 22,24c23,25
 < #define MAX_CLUSTER_SIZE	1024
 < #define MAX_FAT_SIZE		3584	/* 7 sectoren */
 < #define MAX_ROOT_ENTRIES	224	/* 14 sectoren */
 ---
 > #define MAX_CLUSTER_SIZE	4096
 > #define MAX_FAT_SIZE		6144
 > #define MAX_ROOT_ENTRIES	512
 89c90
 < short total_clusters, cluster_size, fat_size,
 ---
 > unsigned short total_clusters, cluster_size, fat_size,
 114a116,141
 > determine()
 > {
 > 		struct dosboot {
 > 			short   jump;
 > 			char    nop;
 > 			char    name[8];
 > 			char    byteps_1;       /* short wuerde um 1byte hochgeschoben */
 > 			char    byteps_2;
 > 			char    secpclus;
 > 			short   reservsec;
 > 			char    fats;
 > 			char    rooten_1;         /* Alignment    */
 > 			char	rooten_2;
 > 			char	totsec_1;
 > 			char	totsec_2;
 > 			char    media;
 > 			short   secpfat;
 > 			short   secptrack;
 > 			short   heads;
 > 			short   hiddensec;
 > 			/* char    fill[482]; */
 > 		}  boot;
 > 		unsigned int bytepers, dirents, totsec;
 > 		char stderr[100];
 > 			/* read Bios-Parameterblock */
 > 		disk_read(0L, &boot, sizeof boot);
 115a143,190
 > 		bytepers = ((int) boot.byteps_2) <<8 + boot.byteps_1;
 > 		dirents =  ((int) boot.rooten_2) <<8 + boot.rooten_1;
 > 		/*totsec  =  ((int) boot.totsec_2) <<8 + boot.totsec_1;*/
 > 		totsec  = boot.totsec_2 <<8;
 > 		totsec  +=  boot.totsec_1;
 >
 > 		total_clusters = totsec/boot.secpclus;
 > 		cluster_size = bytepers * boot.secpclus;
 > 		fat_size = boot.secpfat * bytepers;
 > 		data_start = bytepers + boot.fats* fat_size + dirents * 32;
 > 		root_entries = dirents;	
 > 		sub_entries = boot.secpclus * bytepers/32;
 >
 > #ifdef debug
 > 		sprintf(stderr, "fatsize: %u totclusters: %u totsec %u ( %x %x)\n",
 > 		fat_size,total_clusters, totsec, boot.totsec_2, boot.totsec_1);
 > 		write(2,stderr, strlen(stderr));
 > 		sprintf(stderr, "dirents %u bytepers %u\n", dirents, bytepers);
 > 		write(2,stderr, strlen(stderr));
 > #endif
 >
 > 		/* safety checking */
 > 		if ( boot.fats != 2 && dos_write)
 > 			{print_string (TRUE, "fats != 2 - Can't handle disk\n");
 > 			 leave (2);
 > 			}
 > 		if ( boot.reservsec != 1)
 > 			{print_string (TRUE, "reserved != 1 - Can't handle disk\n");
 > 			 leave (2);
 > 			}
 > 		if ( total_clusters > 4096)
 > 			{print_string (TRUE, "no 12 Bit fat - Can't handle disk\n");
 > 			 leave (2);
 > 			}
 > 		if (fat_size > MAX_FAT_SIZE)
 > 			{print_string (TRUE, "fatsize to big - Can't handle disk\n");
 > 			 leave (2);
 > 			}
 > 		if (cluster_size > MAX_CLUSTER_SIZE)
 > 			{print_string (TRUE, "clustersize to big - Can't handle disk\n");
 > 			 leave (2);
 > 			}
 > 		if ( boot.media &0xFF != HARDDISK)
 > 			{printf("improper media descriptor: %x\n", boot.media);
 > 			 leave (2);
 > 			}
 > }
 >
 184a260,261
 > 	else if (fat[0] == HARDDISK) 		/*Hard Disk*/
 > 		determine();
 199c276
 < 	if (dos_dir) {
 ---
 > 	if (dos_dir && Lflag) {
 211c288,289
 < 		print(STD_OUT, "Root directory:\n", 0);
 ---
 > 		if (Lflag)
 > 			print(STD_OUT, "Root directory:\n", 0);
 213c291,292
 < 		free_blocks();
 ---
 > 		if (Lflag)
 > 			free_blocks();
 229c308
 < 	if (dos_dir)
 ---
 > 	if (dos_dir && Lflag)
 236c315,316
 < 		free_blocks();
 ---
 > 		if (Lflag)
 > 			free_blocks();

------------------------------ end  diff to dosread.c 1.2 ---------------

					Robert Regn