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