drivers/scsi/scsicam.c

   1 /*
   2  * scsicam.c - SCSI CAM support functions, use for HDIO_GETGEO, etc.
   3  *
   4  * Copyright 1993, 1994 Drew Eckhardt
   5  *      Visionary Computing
   6  *      (Unix and Linux consulting and custom programming)
   7  *      drew@Colorado.EDU
   8  *      +1 (303) 786-7975
   9  *
  10  * For more information, please consult the SCSI-CAM draft.
  11  */
  12
  13 #include <linux/module.h>
  14 #include <linux/fs.h>
  15 #include <linux/genhd.h>
  16 #include <linux/kernel.h>
  17 #include <linux/blkdev.h>
  18 #include <linux/buffer_head.h>
  19 #include <asm/unaligned.h>
  20
  21 #include <scsi/scsicam.h>
  22
  23
  24 static int setsize(unsigned long capacity, unsigned int *cyls, unsigned int *hds,
  25                    unsigned int *secs);
  26
  27 unsigned char *scsi_bios_ptable(struct block_device *dev)
  28 {
  29         unsigned char *res = kmalloc(66, GFP_KERNEL);
  30         if (res) {
  31                 struct block_device *bdev = dev->bd_contains;
  32                 Sector sect;
  33                 void *data = read_dev_sector(bdev, 0, &sect);
  34                 if (data) {
  35                         memcpy(res, data + 0x1be, 66);
  36                         put_dev_sector(sect);
  37                 } else {
  38                         kfree(res);
  39                         res = NULL;
  40                 }
  41         }
  42         return res;
  43 }
  44 EXPORT_SYMBOL(scsi_bios_ptable);
  45
  46 /*
  47  * Function : int scsicam_bios_param (struct block_device *bdev, ector_t capacity, int *ip)
  48  *
  49  * Purpose : to determine the BIOS mapping used for a drive in a
  50  *      SCSI-CAM system, storing the results in ip as required
  51  *      by the HDIO_GETGEO ioctl().
  52  *
  53  * Returns : -1 on failure, 0 on success.
  54  *
  55  */
  56
  57 int scsicam_bios_param(struct block_device *bdev, sector_t capacity, int *ip)
  58 {
  59         unsigned char *p;
  60         int ret;
  61
  62         p = scsi_bios_ptable(bdev);
  63         if (!p)
  64                 return -1;
  65
  66         /* try to infer mapping from partition table */
  67         ret = scsi_partsize(p, (unsigned long)capacity, (unsigned int *)ip + 2,
  68                                (unsigned int *)ip + 0, (unsigned int *)ip + 1);
  69         kfree(p);
  70
  71         if (ret == -1) {
  72                 /* pick some standard mapping with at most 1024 cylinders,
  73                    and at most 62 sectors per track - this works up to
  74                    7905 MB */
  75                 ret = setsize((unsigned long)capacity, (unsigned int *)ip + 2,
  76                        (unsigned int *)ip + 0, (unsigned int *)ip + 1);
  77         }
  78
  79         /* if something went wrong, then apparently we have to return
  80            a geometry with more than 1024 cylinders */
  81         if (ret || ip[0] > 255 || ip[1] > 63) {
  82                 if ((capacity >> 11) > 65534) {
  83                         ip[0] = 255;
  84                         ip[1] = 63;
  85                 } else {
  86                         ip[0] = 64;
  87                         ip[1] = 32;
  88                 }
  89
  90                 if (capacity > 65535*63*255)
  91                         ip[2] = 65535;
  92                 else
  93                         ip[2] = (unsigned long)capacity / (ip[0] * ip[1]);
  94         }
  95
  96         return 0;
  97 }
  98 EXPORT_SYMBOL(scsicam_bios_param);
  99
 100 /*
 101  * Function : static int scsi_partsize(unsigned char *buf, unsigned long
 102  *     capacity,unsigned int *cyls, unsigned int *hds, unsigned int *secs);
 103  *
 104  * Purpose : to determine the BIOS mapping used to create the partition
 105  *      table, storing the results in *cyls, *hds, and *secs
 106  *
 107  * Returns : -1 on failure, 0 on success.
 108  *
 109  */
 110
 111 int scsi_partsize(unsigned char *buf, unsigned long capacity,
 112                unsigned int *cyls, unsigned int *hds, unsigned int *secs)
 113 {
 114         struct partition *p = (struct partition *)buf, *largest = NULL;
 115         int i, largest_cyl;
 116         int cyl, ext_cyl, end_head, end_cyl, end_sector;
 117         unsigned int logical_end, physical_end, ext_physical_end;
 118
 119
 120         if (*(unsigned short *) (buf + 64) == 0xAA55) {
 121                 for (largest_cyl = -1, i = 0; i < 4; ++i, ++p) {
 122                         if (!p->sys_ind)
 123                                 continue;
 124 #ifdef DEBUG
 125                         printk("scsicam_bios_param : partition %d has system \n",
 126                                i);
 127 #endif
 128                         cyl = p->cyl + ((p->sector & 0xc0) << 2);
 129                         if (cyl > largest_cyl) {
 130                                 largest_cyl = cyl;
 131                                 largest = p;
 132                         }
 133                 }
 134         }
 135         if (largest) {
 136                 end_cyl = largest->end_cyl + ((largest->end_sector & 0xc0) << 2);
 137                 end_head = largest->end_head;
 138                 end_sector = largest->end_sector & 0x3f;
 139
 140                 if (end_head + 1 == 0 || end_sector == 0)
 141                         return -1;
 142
 143 #ifdef DEBUG
 144                 printk("scsicam_bios_param : end at h = %d, c = %d, s = %d\n",
 145                        end_head, end_cyl, end_sector);
 146 #endif
 147
 148                 physical_end = end_cyl * (end_head + 1) * end_sector +
 149                     end_head * end_sector + end_sector;
 150
 151                 /* This is the actual _sector_ number at the end */
 152                 logical_end = get_unaligned(&largest->start_sect)
 153                     + get_unaligned(&largest->nr_sects);
 154
 155                 /* This is for >1023 cylinders */
 156                 ext_cyl = (logical_end - (end_head * end_sector + end_sector))
 157                     / (end_head + 1) / end_sector;
 158                 ext_physical_end = ext_cyl * (end_head + 1) * end_sector +
 159                     end_head * end_sector + end_sector;
 160
 161 #ifdef DEBUG
 162                 printk("scsicam_bios_param : logical_end=%d physical_end=%d ext_physical_end=%d ext_cyl=%d\n"
 163                   ,logical_end, physical_end, ext_physical_end, ext_cyl);
 164 #endif
 165
 166                 if ((logical_end == physical_end) ||
 167                   (end_cyl == 1023 && ext_physical_end == logical_end)) {
 168                         *secs = end_sector;
 169                         *hds = end_head + 1;
 170                         *cyls = capacity / ((end_head + 1) * end_sector);
 171                         return 0;
 172                 }
 173 #ifdef DEBUG
 174                 printk("scsicam_bios_param : logical (%u) != physical (%u)\n",
 175                        logical_end, physical_end);
 176 #endif
 177         }
 178         return -1;
 179 }
 180 EXPORT_SYMBOL(scsi_partsize);
 181
 182 /*
 183  * Function : static int setsize(unsigned long capacity,unsigned int *cyls,
 184  *      unsigned int *hds, unsigned int *secs);
 185  *
 186  * Purpose : to determine a near-optimal int 0x13 mapping for a
 187  *      SCSI disk in terms of lost space of size capacity, storing
 188  *      the results in *cyls, *hds, and *secs.
 189  *
 190  * Returns : -1 on failure, 0 on success.
 191  *
 192  * Extracted from
 193  *
 194  * WORKING                                                    X3T9.2
 195  * DRAFT                                                        792D
 196  *
 197  *
 198  *                                                        Revision 6
 199  *                                                         10-MAR-94
 200  * Information technology -
 201  * SCSI-2 Common access method
 202  * transport and SCSI interface module
 203  *
 204  * ANNEX A :
 205  *
 206  * setsize() converts a read capacity value to int 13h
 207  * head-cylinder-sector requirements. It minimizes the value for
 208  * number of heads and maximizes the number of cylinders. This
 209  * will support rather large disks before the number of heads
 210  * will not fit in 4 bits (or 6 bits). This algorithm also
 211  * minimizes the number of sectors that will be unused at the end
 212  * of the disk while allowing for very large disks to be
 213  * accommodated. This algorithm does not use physical geometry.
 214  */
 215
 216 static int setsize(unsigned long capacity, unsigned int *cyls, unsigned int *hds,
 217                    unsigned int *secs)
 218 {
 219         unsigned int rv = 0;
 220         unsigned long heads, sectors, cylinders, temp;
 221
 222         cylinders = 1024L;      /* Set number of cylinders to max */
 223         sectors = 62L;          /* Maximize sectors per track */
 224
 225         temp = cylinders * sectors;     /* Compute divisor for heads */
 226         heads = capacity / temp;        /* Compute value for number of heads */
 227         if (capacity % temp) {  /* If no remainder, done! */
 228                 heads++;        /* Else, increment number of heads */
 229                 temp = cylinders * heads;       /* Compute divisor for sectors */
 230                 sectors = capacity / temp;      /* Compute value for sectors per
 231                                                    track */
 232                 if (capacity % temp) {  /* If no remainder, done! */
 233                         sectors++;      /* Else, increment number of sectors */
 234                         temp = heads * sectors;         /* Compute divisor for cylinders */
 235                         cylinders = capacity / temp;    /* Compute number of cylinders */
 236                 }
 237         }
 238         if (cylinders == 0)
 239                 rv = (unsigned) -1;     /* Give error if 0 cylinders */
 240
 241         *cyls = (unsigned int) cylinders;       /* Stuff return values */
 242         *secs = (unsigned int) sectors;
 243         *hds = (unsigned int) heads;
 244         return (rv);
 245 }