summaryrefslogtreecommitdiffstats
path: root/drivers/scsi/scsicam.c
blob: 9a7c32e23461271f72d23fc4a1b1ff2ba5db7e88 (plain)
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
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
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
/*
 * 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.
 */

#define __NO_VERSION__
#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);


/*
 * 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 */ )
{
	struct buffer_head *bh;
	int ret_code;
	int size = disk->capacity;
	unsigned long temp_cyl;

	int ma = MAJOR(dev);
	int mi = (MINOR(dev) & ~0xf);

	int block = 1024; 

	if(blksize_size[ma])
		block = blksize_size[ma][mi];
		
	if (!(bh = bread(MKDEV(ma,mi), 0, block)))
		return -1;

	/* try to infer mapping from partition table */
	ret_code = scsi_partsize(bh, (unsigned long) size, (unsigned int *) ip + 2,
		       (unsigned int *) ip + 0, (unsigned int *) ip + 1);
	brelse(bh);

	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;
}

/*
 * Function : static int scsi_partsize(struct buffer_head *bh, unsigned long 
 *     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.
 *
 */

int scsi_partsize(struct buffer_head *bh, unsigned long capacity,
	       unsigned int *cyls, unsigned int *hds, unsigned int *secs)
{
	struct partition *p, *largest = NULL;
	int i, largest_cyl;
	int cyl, ext_cyl, end_head, end_cyl, end_sector;
	unsigned int logical_end, physical_end, ext_physical_end;


	if (*(unsigned short *) (bh->b_data + 510) == 0xAA55) {
		for (largest_cyl = -1, p = (struct partition *)
		     (0x1BE + bh->b_data), i = 0; i < 4; ++i, ++p) {
			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);
}