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         u64 capacity64 = capacity;      /* Suppress gcc warning */
  61         int ret;
  62
  63         p = scsi_bios_ptable(bdev);
  64         if (!p)
  65                 return -1;
  66
  67         /* try to infer mapping from partition table */
  68         ret = scsi_partsize(p, (unsigned long)capacity, (unsigned int *)ip + 2,
  69                                (unsigned int *)ip + 0, (unsigned int *)ip + 1);
  70         kfree(p);
  71
  72         if (ret == -1 && capacity64 < (1ULL << 32)) {
  73                 /* pick some standard mapping with at most 1024 cylinders,
  74                    and at most 62 sectors per track - this works up to
  75                    7905 MB */
  76                 ret = setsize((unsigned long)capacity, (unsigned int *)ip + 2,
  77                        (unsigned int *)ip + 0, (unsigned int *)ip + 1);
  78         }
  79
  80         /* if something went wrong, then apparently we have to return
  81            a geometry with more than 1024 cylinders */
  82         if (ret || ip[0] > 255 || ip[1] > 63) {
  83                 if ((capacity >> 11) > 65534) {
  84                         ip[0] = 255;
  85                         ip[1] = 63;
  86                 } else {
  87                         ip[0] = 64;
  88                         ip[1] = 32;
  89                 }
  90
  91                 if (capacity > 65535*63*255)
  92                         ip[2] = 65535;
  93                 else
  94                         ip[2] = (unsigned long)capacity / (ip[0] * ip[1]);
  95         }
  96
  97         return 0;
  98 }
  99 EXPORT_SYMBOL(scsicam_bios_param);
 100
 101 /*
 102  * Function : static int scsi_partsize(unsigned char *buf, unsigned long
 103  *     capacity,unsigned int *cyls, unsigned int *hds, unsigned int *secs);
 104  *
 105  * Purpose : to determine the BIOS mapping used to create the partition
 106  *      table, storing the results in *cyls, *hds, and *secs
 107  *
 108  * Returns : -1 on failure, 0 on success.
 109  *
 110  */
 111
 112 int scsi_partsize(unsigned char *buf, unsigned long capacity,
 113                unsigned int *cyls, unsigned int *hds, unsigned int *secs)
 114 {
 115         struct partition *p = (struct partition *)buf, *largest = NULL;
 116         int i, largest_cyl;
 117         int cyl, ext_cyl, end_head, end_cyl, end_sector;
 118         unsigned int logical_end, physical_end, ext_physical_end;
 119
 120
 121         if (*(unsigned short *) (buf + 64) == 0xAA55) {
 122                 for (largest_cyl = -1, i = 0; i < 4; ++i, ++p) {
 123                         if (!p->sys_ind)
 124                                 continue;
 125 #ifdef DEBUG
 126                         printk("scsicam_bios_param : partition %d has system \n",
 127                                i);
 128 #endif
 129                         cyl = p->cyl + ((p->sector & 0xc0) << 2);
 130                         if (cyl > largest_cyl) {
 131                                 largest_cyl = cyl;
 132                                 largest = p;
 133                         }
 134                 }
 135         }
 136         if (largest) {
 137                 end_cyl = largest->end_cyl + ((largest->end_sector & 0xc0) << 2);
 138                 end_head = largest->end_head;
 139                 end_sector = largest->end_sector & 0x3f;
 140
 141                 if (end_head + 1 == 0 || end_sector == 0)
 142                         return -1;
 143
 144 #ifdef DEBUG
 145                 printk("scsicam_bios_param : end at h = %d, c = %d, s = %d\n",
 146                        end_head, end_cyl, end_sector);
 147 #endif
 148
 149                 physical_end = end_cyl * (end_head + 1) * end_sector +
 150                     end_head * end_sector + end_sector;
 151
 152                 /* This is the actual _sector_ number at the end */
 153                 logical_end = get_unaligned(&largest->start_sect)
 154                     + get_unaligned(&largest->nr_sects);
 155
 156                 /* This is for >1023 cylinders */
 157                 ext_cyl = (logical_end - (end_head * end_sector + end_sector))
 158                     / (end_head + 1) / end_sector;
 159                 ext_physical_end = ext_cyl * (end_head + 1) * end_sector +
 160                     end_head * end_sector + end_sector;
 161
 162 #ifdef DEBUG
 163                 printk("scsicam_bios_param : logical_end=%d physical_end=%d ext_physical_end=%d ext_cyl=%d\n"
 164                   ,logical_end, physical_end, ext_physical_end, ext_cyl);
 165 #endif
 166
 167                 if ((logical_end == physical_end) ||
 168                   (end_cyl == 1023 && ext_physical_end == logical_end)) {
 169                         *secs = end_sector;
 170                         *hds = end_head + 1;
 171                         *cyls = capacity / ((end_head + 1) * end_sector);
 172                         return 0;
 173                 }
 174 #ifdef DEBUG
 175                 printk("scsicam_bios_param : logical (%u) != physical (%u)\n",
 176                        logical_end, physical_end);
 177 #endif
 178         }
 179         return -1;
 180 }
 181 EXPORT_SYMBOL(scsi_partsize);
 182
 183 /*
 184  * Function : static int setsize(unsigned long capacity,unsigned int *cyls,
 185  *      unsigned int *hds, unsigned int *secs);
 186  *
 187  * Purpose : to determine a near-optimal int 0x13 mapping for a
 188  *      SCSI disk in terms of lost space of size capacity, storing
 189  *      the results in *cyls, *hds, and *secs.
 190  *
 191  * Returns : -1 on failure, 0 on success.
 192  *
 193  * Extracted from
 194  *
 195  * WORKING                                                    X3T9.2
 196  * DRAFT                                                        792D
 197  *
 198  *
 199  *                                                        Revision 6
 200  *                                                         10-MAR-94
 201  * Information technology -
 202  * SCSI-2 Common access method
 203  * transport and SCSI interface module
 204  *
 205  * ANNEX A :
 206  *
 207  * setsize() converts a read capacity value to int 13h
 208  * head-cylinder-sector requirements. It minimizes the value for
 209  * number of heads and maximizes the number of cylinders. This
 210  * will support rather large disks before the number of heads
 211  * will not fit in 4 bits (or 6 bits). This algorithm also
 212  * minimizes the number of sectors that will be unused at the end
 213  * of the disk while allowing for very large disks to be
 214  * accommodated. This algorithm does not use physical geometry.
 215  */
 216
 217 static int setsize(unsigned long capacity, unsigned int *cyls, unsigned int *hds,
 218                    unsigned int *secs)
 219 {
 220         unsigned int rv = 0;
 221         unsigned long heads, sectors, cylinders, temp;
 222
 223         cylinders = 1024L;      /* Set number of cylinders to max */
 224         sectors = 62L;          /* Maximize sectors per track */
 225
 226         temp = cylinders * sectors;     /* Compute divisor for heads */
 227         heads = capacity / temp;        /* Compute value for number of heads */
 228         if (capacity % temp) {  /* If no remainder, done! */
 229                 heads++;        /* Else, increment number of heads */
 230                 temp = cylinders * heads;       /* Compute divisor for sectors */
 231                 sectors = capacity / temp;      /* Compute value for sectors per
 232                                                    track */
 233                 if (capacity % temp) {  /* If no remainder, done! */
 234                         sectors++;      /* Else, increment number of sectors */
 235                         temp = heads * sectors;         /* Compute divisor for cylinders */
 236                         cylinders = capacity / temp;    /* Compute number of cylinders */
 237                 }
 238         }
 239         if (cylinders == 0)
 240                 rv = (unsigned) -1;     /* Give error if 0 cylinders */
 241
 242         *cyls = (unsigned int) cylinders;       /* Stuff return values */
 243         *secs = (unsigned int) sectors;
 244         *hds = (unsigned int) heads;
 245         return (rv);
 246 }