blob: b78354fc4b1715fe0ffc08c3500a9937075e245f [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
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
24static int setsize(unsigned long capacity, unsigned int *cyls, unsigned int *hds,
25 unsigned int *secs);
26
27unsigned 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}
44EXPORT_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
57int 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}
98EXPORT_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
111int 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}
180EXPORT_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
216static 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}