scsicam.c 7.29 KB
Newer Older
Linus Torvalds's avatar
Linus Torvalds committed
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27
/*
 * scsicam.c - SCSI CAM support functions, use for HDIO_GETGEO, etc.
 *
 * Copyright 1993, 1994 Drew Eckhardt
 *      Visionary Computing 
 *      (Unix and Linux consulting and custom programming)
 *      drew@Colorado.EDU
 *      +1 (303) 786-7975
 *
 * For more information, please consult the SCSI-CAM draft.
 */

#include <linux/module.h>

#include <linux/fs.h>
#include <linux/genhd.h>
#include <linux/kernel.h>
#include <linux/blk.h>
#include <asm/unaligned.h>
#include "scsi.h"
#include "hosts.h"
#include "sd.h"
#include <scsi/scsicam.h>

static int setsize(unsigned long capacity, unsigned int *cyls, unsigned int *hds,
		   unsigned int *secs);

Linus Torvalds's avatar
Linus Torvalds committed
28 29
unsigned char *scsi_bios_ptable(kdev_t dev)
{
Linus Torvalds's avatar
Linus Torvalds committed
30
	struct block_device *bdev;
Linus Torvalds's avatar
Linus Torvalds committed
31
	unsigned char *res = kmalloc(66, GFP_KERNEL);
Linus Torvalds's avatar
Linus Torvalds committed
32
	kdev_t rdev = mk_kdev(major(dev), minor(dev) & ~0x0f);
Linus Torvalds's avatar
Linus Torvalds committed
33 34

	if (res) {
Linus Torvalds's avatar
Linus Torvalds committed
35 36 37 38 39 40 41 42 43 44 45 46 47 48 49
		struct buffer_head *bh;
		int err;

		bdev = bdget(kdev_t_to_nr(rdev));
		if (!bdev)
			goto fail;
		err = blkdev_get(bdev, FMODE_READ, 0, BDEV_FILE);
		if (err)
			goto fail;
		bh = __bread(bdev, 0, block_size(rdev));
		if (!bh)
			goto fail2;
		memcpy(res, bh->b_data + 0x1be, 66);
		brelse(bh);
		blkdev_put(bdev, BDEV_FILE);
Linus Torvalds's avatar
Linus Torvalds committed
50 51
	}
	return res;
Linus Torvalds's avatar
Linus Torvalds committed
52 53 54 55 56
fail2:
	blkdev_put(bdev, BDEV_FILE);
fail:
	kfree(res);
	return NULL;
Linus Torvalds's avatar
Linus Torvalds committed
57
}
Linus Torvalds's avatar
Linus Torvalds committed
58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76

/*
 * Function : int scsicam_bios_param (Disk *disk, int dev, int *ip)
 *
 * Purpose : to determine the BIOS mapping used for a drive in a 
 *      SCSI-CAM system, storing the results in ip as required
 *      by the HDIO_GETGEO ioctl().
 *
 * Returns : -1 on failure, 0 on success.
 *
 */

int scsicam_bios_param(Disk * disk,	/* SCSI disk */
		       kdev_t dev,	/* Device major, minor */
		  int *ip /* Heads, sectors, cylinders in that order */ )
{
	int ret_code;
	int size = disk->capacity;
	unsigned long temp_cyl;
Linus Torvalds's avatar
Linus Torvalds committed
77
	unsigned char *p = scsi_bios_ptable(dev);
Linus Torvalds's avatar
Linus Torvalds committed
78

Linus Torvalds's avatar
Linus Torvalds committed
79
	if (!p)
Linus Torvalds's avatar
Linus Torvalds committed
80 81 82
		return -1;

	/* try to infer mapping from partition table */
Linus Torvalds's avatar
Linus Torvalds committed
83
	ret_code = scsi_partsize(p, (unsigned long) size, (unsigned int *) ip + 2,
Linus Torvalds's avatar
Linus Torvalds committed
84
		       (unsigned int *) ip + 0, (unsigned int *) ip + 1);
Linus Torvalds's avatar
Linus Torvalds committed
85
	kfree(p);
Linus Torvalds's avatar
Linus Torvalds committed
86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109

	if (ret_code == -1) {
		/* pick some standard mapping with at most 1024 cylinders,
		   and at most 62 sectors per track - this works up to
		   7905 MB */
		ret_code = setsize((unsigned long) size, (unsigned int *) ip + 2,
		       (unsigned int *) ip + 0, (unsigned int *) ip + 1);
	}
	/* if something went wrong, then apparently we have to return
	   a geometry with more than 1024 cylinders */
	if (ret_code || ip[0] > 255 || ip[1] > 63) {
		ip[0] = 64;
		ip[1] = 32;
		temp_cyl = size / (ip[0] * ip[1]);
		if (temp_cyl > 65534) {
			ip[0] = 255;
			ip[1] = 63;
		}
		ip[2] = size / (ip[0] * ip[1]);
	}
	return 0;
}

/*
Linus Torvalds's avatar
Linus Torvalds committed
110
 * Function : static int scsi_partsize(unsigned char *buf, unsigned long 
Linus Torvalds's avatar
Linus Torvalds committed
111 112 113 114 115 116 117 118 119
 *     capacity,unsigned int *cyls, unsigned int *hds, unsigned int *secs);
 *
 * Purpose : to determine the BIOS mapping used to create the partition
 *      table, storing the results in *cyls, *hds, and *secs 
 *
 * Returns : -1 on failure, 0 on success.
 *
 */

Linus Torvalds's avatar
Linus Torvalds committed
120
int scsi_partsize(unsigned char *buf, unsigned long capacity,
Linus Torvalds's avatar
Linus Torvalds committed
121 122
	       unsigned int *cyls, unsigned int *hds, unsigned int *secs)
{
Linus Torvalds's avatar
Linus Torvalds committed
123
	struct partition *p = (struct partition *)buf, *largest = NULL;
Linus Torvalds's avatar
Linus Torvalds committed
124 125 126 127 128
	int i, largest_cyl;
	int cyl, ext_cyl, end_head, end_cyl, end_sector;
	unsigned int logical_end, physical_end, ext_physical_end;


129
	if (*(unsigned short *) (buf + 64) == 0xAA55) {
Linus Torvalds's avatar
Linus Torvalds committed
130
		for (largest_cyl = -1, i = 0; i < 4; ++i, ++p) {
Linus Torvalds's avatar
Linus Torvalds committed
131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253
			if (!p->sys_ind)
				continue;
#ifdef DEBUG
			printk("scsicam_bios_param : partition %d has system \n",
			       i);
#endif
			cyl = p->cyl + ((p->sector & 0xc0) << 2);
			if (cyl > largest_cyl) {
				largest_cyl = cyl;
				largest = p;
			}
		}
	}
	if (largest) {
		end_cyl = largest->end_cyl + ((largest->end_sector & 0xc0) << 2);
		end_head = largest->end_head;
		end_sector = largest->end_sector & 0x3f;

		if (end_head + 1 == 0 || end_sector == 0)
			return -1;

#ifdef DEBUG
		printk("scsicam_bios_param : end at h = %d, c = %d, s = %d\n",
		       end_head, end_cyl, end_sector);
#endif

		physical_end = end_cyl * (end_head + 1) * end_sector +
		    end_head * end_sector + end_sector;

		/* This is the actual _sector_ number at the end */
		logical_end = get_unaligned(&largest->start_sect)
		    + get_unaligned(&largest->nr_sects);

		/* This is for >1023 cylinders */
		ext_cyl = (logical_end - (end_head * end_sector + end_sector))
		    / (end_head + 1) / end_sector;
		ext_physical_end = ext_cyl * (end_head + 1) * end_sector +
		    end_head * end_sector + end_sector;

#ifdef DEBUG
		printk("scsicam_bios_param : logical_end=%d physical_end=%d ext_physical_end=%d ext_cyl=%d\n"
		  ,logical_end, physical_end, ext_physical_end, ext_cyl);
#endif

		if ((logical_end == physical_end) ||
		  (end_cyl == 1023 && ext_physical_end == logical_end)) {
			*secs = end_sector;
			*hds = end_head + 1;
			*cyls = capacity / ((end_head + 1) * end_sector);
			return 0;
		}
#ifdef DEBUG
		printk("scsicam_bios_param : logical (%u) != physical (%u)\n",
		       logical_end, physical_end);
#endif
	}
	return -1;
}

/*
 * Function : static int setsize(unsigned long capacity,unsigned int *cyls,
 *      unsigned int *hds, unsigned int *secs);
 *
 * Purpose : to determine a near-optimal int 0x13 mapping for a
 *      SCSI disk in terms of lost space of size capacity, storing
 *      the results in *cyls, *hds, and *secs.
 *
 * Returns : -1 on failure, 0 on success.
 *
 * Extracted from
 *
 * WORKING                                                    X3T9.2
 * DRAFT                                                        792D
 *
 *
 *                                                        Revision 6
 *                                                         10-MAR-94
 * Information technology -
 * SCSI-2 Common access method
 * transport and SCSI interface module
 * 
 * ANNEX A :
 *
 * setsize() converts a read capacity value to int 13h
 * head-cylinder-sector requirements. It minimizes the value for
 * number of heads and maximizes the number of cylinders. This
 * will support rather large disks before the number of heads
 * will not fit in 4 bits (or 6 bits). This algorithm also
 * minimizes the number of sectors that will be unused at the end
 * of the disk while allowing for very large disks to be
 * accommodated. This algorithm does not use physical geometry. 
 */

static int setsize(unsigned long capacity, unsigned int *cyls, unsigned int *hds,
		   unsigned int *secs)
{
	unsigned int rv = 0;
	unsigned long heads, sectors, cylinders, temp;

	cylinders = 1024L;	/* Set number of cylinders to max */
	sectors = 62L;		/* Maximize sectors per track */

	temp = cylinders * sectors;	/* Compute divisor for heads */
	heads = capacity / temp;	/* Compute value for number of heads */
	if (capacity % temp) {	/* If no remainder, done! */
		heads++;	/* Else, increment number of heads */
		temp = cylinders * heads;	/* Compute divisor for sectors */
		sectors = capacity / temp;	/* Compute value for sectors per
						   track */
		if (capacity % temp) {	/* If no remainder, done! */
			sectors++;	/* Else, increment number of sectors */
			temp = heads * sectors;		/* Compute divisor for cylinders */
			cylinders = capacity / temp;	/* Compute number of cylinders */
		}
	}
	if (cylinders == 0)
		rv = (unsigned) -1;	/* Give error if 0 cylinders */

	*cyls = (unsigned int) cylinders;	/* Stuff return values */
	*secs = (unsigned int) sectors;
	*hds = (unsigned int) heads;
	return (rv);
}