src/drivers/disk/floppy.c

   1 #if     (TRY_FLOPPY_FIRST > 0)
   2
   3 /*
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public License as
   6  * published by the Free Software Foundation; either version 2, or (at
   7  * your option) any later version.
   8  */
   9
  10 #include "etherboot.h"
  11
  12 #define BOOTSECT ((char *)0x7C00)
  13 #define BOOTSIG  ((unsigned short *)BOOTSECT)[0xFF]
  14 #define PARTTAB  ((partentry *)(BOOTSECT+0x1BE))
  15
  16 typedef struct partentry {
  17         unsigned char flags;
  18         unsigned char start_head;
  19         unsigned char start_sector;
  20         unsigned char start_cylinder;
  21         unsigned char type;
  22         unsigned char end_head;
  23         unsigned char end_sector;
  24         unsigned char end_cylinder;
  25         unsigned long offset;
  26         unsigned long length;
  27 } partentry;
  28
  29 static unsigned int disk_read_retry(int dev,int c,int h,int s)
  30 {
  31         int retry = 3,rc;
  32
  33         while (retry-- && (rc = pcbios_disk_read(dev,c,h,s,BOOTSECT)) != 0);
  34         if (BOOTSIG != 0xAA55) {
  35                 printf("not a boot sector");
  36                 return(0xFFFF); }
  37         return(rc);
  38 }
  39
  40 int bootdisk(int dev,int part)
  41 {
  42         int rc;
  43
  44         disk_init();
  45         if ((rc = disk_read_retry(dev,0,0,1)) != 0) {
  46         readerr:
  47                 if (rc != 0xFFFF)
  48                         printf("read error (%#hhX)",rc/256);
  49                 return(0); }
  50         if (part) {
  51                 partentry *ptr;
  52
  53                 if (part >= 5) {
  54                         int i;
  55                         for (i = 0, ptr = PARTTAB; ptr->type != 5; ptr++)
  56                                 if (++i == 4) {
  57                                         printf("partition not found");
  58                                         return(0); }
  59                         if ((rc = disk_read_retry(dev,
  60                                                   ptr->start_cylinder,
  61                                                   ptr->start_head,
  62                                                   ptr->start_sector)) != 0)
  63                                 goto readerr;
  64                         part -= 4; }
  65                 if (!(ptr = PARTTAB-1+part)->type) {
  66                         printf("empty partition");
  67                         return(0); }
  68                 if ((rc = disk_read_retry(dev,
  69                                           ptr->start_cylinder,
  70                                           ptr->start_head,
  71                                           ptr->start_sector)) != 0)
  72                         goto readerr; }
  73         cleanup();
  74         gateA20_unset();
  75         /* Set %edx to device number to emulate BIOS
  76            Fortunately %edx is not used after this */
  77         __asm__("movl %0,%%edx" : : "g" (dev));
  78         xstart((unsigned long)BOOTSECT, 0, 0);
  79         return(0);
  80 }
  81
  82 #endif
  83
  84 /*
  85  * Local variables:
  86  *  c-basic-offset: 8
  87  * End:
  88  */