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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/slab.h>
15#include <linux/fs.h>
16#include <linux/genhd.h>
17#include <linux/kernel.h>
18#include <linux/blkdev.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
27/**
28 * scsi_bios_ptable - Read PC partition table out of first sector of device.
29 * @dev: from this device
30 *
31 * Description: Reads the first sector from the device and returns %0x42 bytes
32 * starting at offset %0x1be.
33 * Returns: partition table in kmalloc(GFP_KERNEL) memory, or NULL on error.
34 */
35unsigned char *scsi_bios_ptable(struct block_device *dev)
36{
37 unsigned char *res = kmalloc(66, GFP_KERNEL);
38 if (res) {
39 struct block_device *bdev = dev->bd_contains;
40 Sector sect;
41 void *data = read_dev_sector(bdev, 0, §);
42 if (data) {
43 memcpy(res, data + 0x1be, 66);
44 put_dev_sector(sect);
45 } else {
46 kfree(res);
47 res = NULL;
48 }
49 }
50 return res;
51}
52EXPORT_SYMBOL(scsi_bios_ptable);
53
54/**
55 * scsicam_bios_param - Determine geometry of a disk in cylinders/heads/sectors.
56 * @bdev: which device
57 * @capacity: size of the disk in sectors
58 * @ip: return value: ip[0]=heads, ip[1]=sectors, ip[2]=cylinders
59 *
60 * Description : determine the BIOS mapping/geometry used for a drive in a
61 * SCSI-CAM system, storing the results in ip as required
62 * by the HDIO_GETGEO ioctl().
63 *
64 * Returns : -1 on failure, 0 on success.
65 */
66
67int scsicam_bios_param(struct block_device *bdev, sector_t capacity, int *ip)
68{
69 unsigned char *p;
70 u64 capacity64 = capacity; /* Suppress gcc warning */
71 int ret;
72
73 p = scsi_bios_ptable(bdev);
74 if (!p)
75 return -1;
76
77 /* try to infer mapping from partition table */
78 ret = scsi_partsize(p, (unsigned long)capacity, (unsigned int *)ip + 2,
79 (unsigned int *)ip + 0, (unsigned int *)ip + 1);
80 kfree(p);
81
82 if (ret == -1 && capacity64 < (1ULL << 32)) {
83 /* pick some standard mapping with at most 1024 cylinders,
84 and at most 62 sectors per track - this works up to
85 7905 MB */
86 ret = setsize((unsigned long)capacity, (unsigned int *)ip + 2,
87 (unsigned int *)ip + 0, (unsigned int *)ip + 1);
88 }
89
90 /* if something went wrong, then apparently we have to return
91 a geometry with more than 1024 cylinders */
92 if (ret || ip[0] > 255 || ip[1] > 63) {
93 if ((capacity >> 11) > 65534) {
94 ip[0] = 255;
95 ip[1] = 63;
96 } else {
97 ip[0] = 64;
98 ip[1] = 32;
99 }
100
101 if (capacity > 65535*63*255)
102 ip[2] = 65535;
103 else
104 ip[2] = (unsigned long)capacity / (ip[0] * ip[1]);
105 }
106
107 return 0;
108}
109EXPORT_SYMBOL(scsicam_bios_param);
110
111/**
112 * scsi_partsize - Parse cylinders/heads/sectors from PC partition table
113 * @buf: partition table, see scsi_bios_ptable()
114 * @capacity: size of the disk in sectors
115 * @cyls: put cylinders here
116 * @hds: put heads here
117 * @secs: put sectors here
118 *
119 * Description: determine the BIOS mapping/geometry used to create the partition
120 * table, storing the results in *cyls, *hds, and *secs
121 *
122 * Returns: -1 on failure, 0 on success.
123 */
124
125int scsi_partsize(unsigned char *buf, unsigned long capacity,
126 unsigned int *cyls, unsigned int *hds, unsigned int *secs)
127{
128 struct partition *p = (struct partition *)buf, *largest = NULL;
129 int i, largest_cyl;
130 int cyl, ext_cyl, end_head, end_cyl, end_sector;
131 unsigned int logical_end, physical_end, ext_physical_end;
132
133
134 if (*(unsigned short *) (buf + 64) == 0xAA55) {
135 for (largest_cyl = -1, i = 0; i < 4; ++i, ++p) {
136 if (!p->sys_ind)
137 continue;
138#ifdef DEBUG
139 printk("scsicam_bios_param : partition %d has system \n",
140 i);
141#endif
142 cyl = p->cyl + ((p->sector & 0xc0) << 2);
143 if (cyl > largest_cyl) {
144 largest_cyl = cyl;
145 largest = p;
146 }
147 }
148 }
149 if (largest) {
150 end_cyl = largest->end_cyl + ((largest->end_sector & 0xc0) << 2);
151 end_head = largest->end_head;
152 end_sector = largest->end_sector & 0x3f;
153
154 if (end_head + 1 == 0 || end_sector == 0)
155 return -1;
156
157#ifdef DEBUG
158 printk("scsicam_bios_param : end at h = %d, c = %d, s = %d\n",
159 end_head, end_cyl, end_sector);
160#endif
161
162 physical_end = end_cyl * (end_head + 1) * end_sector +
163 end_head * end_sector + end_sector;
164
165 /* This is the actual _sector_ number at the end */
166 logical_end = get_unaligned_le32(&largest->start_sect)
167 + get_unaligned_le32(&largest->nr_sects);
168
169 /* This is for >1023 cylinders */
170 ext_cyl = (logical_end - (end_head * end_sector + end_sector))
171 / (end_head + 1) / end_sector;
172 ext_physical_end = ext_cyl * (end_head + 1) * end_sector +
173 end_head * end_sector + end_sector;
174
175#ifdef DEBUG
176 printk("scsicam_bios_param : logical_end=%d physical_end=%d ext_physical_end=%d ext_cyl=%d\n"
177 ,logical_end, physical_end, ext_physical_end, ext_cyl);
178#endif
179
180 if ((logical_end == physical_end) ||
181 (end_cyl == 1023 && ext_physical_end == logical_end)) {
182 *secs = end_sector;
183 *hds = end_head + 1;
184 *cyls = capacity / ((end_head + 1) * end_sector);
185 return 0;
186 }
187#ifdef DEBUG
188 printk("scsicam_bios_param : logical (%u) != physical (%u)\n",
189 logical_end, physical_end);
190#endif
191 }
192 return -1;
193}
194EXPORT_SYMBOL(scsi_partsize);
195
196/*
197 * Function : static int setsize(unsigned long capacity,unsigned int *cyls,
198 * unsigned int *hds, unsigned int *secs);
199 *
200 * Purpose : to determine a near-optimal int 0x13 mapping for a
201 * SCSI disk in terms of lost space of size capacity, storing
202 * the results in *cyls, *hds, and *secs.
203 *
204 * Returns : -1 on failure, 0 on success.
205 *
206 * Extracted from
207 *
208 * WORKING X3T9.2
209 * DRAFT 792D
210 * see http://www.t10.org/ftp/t10/drafts/cam/cam-r12b.pdf
211 *
212 * Revision 6
213 * 10-MAR-94
214 * Information technology -
215 * SCSI-2 Common access method
216 * transport and SCSI interface module
217 *
218 * ANNEX A :
219 *
220 * setsize() converts a read capacity value to int 13h
221 * head-cylinder-sector requirements. It minimizes the value for
222 * number of heads and maximizes the number of cylinders. This
223 * will support rather large disks before the number of heads
224 * will not fit in 4 bits (or 6 bits). This algorithm also
225 * minimizes the number of sectors that will be unused at the end
226 * of the disk while allowing for very large disks to be
227 * accommodated. This algorithm does not use physical geometry.
228 */
229
230static int setsize(unsigned long capacity, unsigned int *cyls, unsigned int *hds,
231 unsigned int *secs)
232{
233 unsigned int rv = 0;
234 unsigned long heads, sectors, cylinders, temp;
235
236 cylinders = 1024L; /* Set number of cylinders to max */
237 sectors = 62L; /* Maximize sectors per track */
238
239 temp = cylinders * sectors; /* Compute divisor for heads */
240 heads = capacity / temp; /* Compute value for number of heads */
241 if (capacity % temp) { /* If no remainder, done! */
242 heads++; /* Else, increment number of heads */
243 temp = cylinders * heads; /* Compute divisor for sectors */
244 sectors = capacity / temp; /* Compute value for sectors per
245 track */
246 if (capacity % temp) { /* If no remainder, done! */
247 sectors++; /* Else, increment number of sectors */
248 temp = heads * sectors; /* Compute divisor for cylinders */
249 cylinders = capacity / temp; /* Compute number of cylinders */
250 }
251 }
252 if (cylinders == 0)
253 rv = (unsigned) -1; /* Give error if 0 cylinders */
254
255 *cyls = (unsigned int) cylinders; /* Stuff return values */
256 *secs = (unsigned int) sectors;
257 *hds = (unsigned int) heads;
258 return (rv);
259}
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * scsicam.c - SCSI CAM support functions, use for HDIO_GETGEO, etc.
4 *
5 * Copyright 1993, 1994 Drew Eckhardt
6 * Visionary Computing
7 * (Unix and Linux consulting and custom programming)
8 * drew@Colorado.EDU
9 * +1 (303) 786-7975
10 *
11 * For more information, please consult the SCSI-CAM draft.
12 */
13
14#include <linux/module.h>
15#include <linux/slab.h>
16#include <linux/fs.h>
17#include <linux/genhd.h>
18#include <linux/kernel.h>
19#include <linux/blkdev.h>
20#include <linux/msdos_partition.h>
21#include <asm/unaligned.h>
22
23#include <scsi/scsicam.h>
24
25/**
26 * scsi_bios_ptable - Read PC partition table out of first sector of device.
27 * @dev: from this device
28 *
29 * Description: Reads the first sector from the device and returns %0x42 bytes
30 * starting at offset %0x1be.
31 * Returns: partition table in kmalloc(GFP_KERNEL) memory, or NULL on error.
32 */
33unsigned char *scsi_bios_ptable(struct block_device *dev)
34{
35 struct address_space *mapping = dev->bd_contains->bd_inode->i_mapping;
36 unsigned char *res = NULL;
37 struct page *page;
38
39 page = read_mapping_page(mapping, 0, NULL);
40 if (IS_ERR(page))
41 return NULL;
42
43 if (!PageError(page))
44 res = kmemdup(page_address(page) + 0x1be, 66, GFP_KERNEL);
45 put_page(page);
46 return res;
47}
48EXPORT_SYMBOL(scsi_bios_ptable);
49
50/**
51 * scsi_partsize - Parse cylinders/heads/sectors from PC partition table
52 * @bdev: block device to parse
53 * @capacity: size of the disk in sectors
54 * @geom: output in form of [hds, cylinders, sectors]
55 *
56 * Determine the BIOS mapping/geometry used to create the partition
57 * table, storing the results in @geom.
58 *
59 * Returns: %false on failure, %true on success.
60 */
61bool scsi_partsize(struct block_device *bdev, sector_t capacity, int geom[3])
62{
63 int cyl, ext_cyl, end_head, end_cyl, end_sector;
64 unsigned int logical_end, physical_end, ext_physical_end;
65 struct msdos_partition *p, *largest = NULL;
66 void *buf;
67 int ret = false;
68
69 buf = scsi_bios_ptable(bdev);
70 if (!buf)
71 return false;
72
73 if (*(unsigned short *) (buf + 64) == 0xAA55) {
74 int largest_cyl = -1, i;
75
76 for (i = 0, p = buf; i < 4; i++, p++) {
77 if (!p->sys_ind)
78 continue;
79#ifdef DEBUG
80 printk("scsicam_bios_param : partition %d has system \n",
81 i);
82#endif
83 cyl = p->cyl + ((p->sector & 0xc0) << 2);
84 if (cyl > largest_cyl) {
85 largest_cyl = cyl;
86 largest = p;
87 }
88 }
89 }
90 if (largest) {
91 end_cyl = largest->end_cyl + ((largest->end_sector & 0xc0) << 2);
92 end_head = largest->end_head;
93 end_sector = largest->end_sector & 0x3f;
94
95 if (end_head + 1 == 0 || end_sector == 0)
96 goto out_free_buf;
97
98#ifdef DEBUG
99 printk("scsicam_bios_param : end at h = %d, c = %d, s = %d\n",
100 end_head, end_cyl, end_sector);
101#endif
102
103 physical_end = end_cyl * (end_head + 1) * end_sector +
104 end_head * end_sector + end_sector;
105
106 /* This is the actual _sector_ number at the end */
107 logical_end = get_unaligned_le32(&largest->start_sect)
108 + get_unaligned_le32(&largest->nr_sects);
109
110 /* This is for >1023 cylinders */
111 ext_cyl = (logical_end - (end_head * end_sector + end_sector))
112 / (end_head + 1) / end_sector;
113 ext_physical_end = ext_cyl * (end_head + 1) * end_sector +
114 end_head * end_sector + end_sector;
115
116#ifdef DEBUG
117 printk("scsicam_bios_param : logical_end=%d physical_end=%d ext_physical_end=%d ext_cyl=%d\n"
118 ,logical_end, physical_end, ext_physical_end, ext_cyl);
119#endif
120
121 if (logical_end == physical_end ||
122 (end_cyl == 1023 && ext_physical_end == logical_end)) {
123 geom[0] = end_head + 1;
124 geom[1] = end_sector;
125 geom[2] = (unsigned long)capacity /
126 ((end_head + 1) * end_sector);
127 ret = true;
128 goto out_free_buf;
129 }
130#ifdef DEBUG
131 printk("scsicam_bios_param : logical (%u) != physical (%u)\n",
132 logical_end, physical_end);
133#endif
134 }
135
136out_free_buf:
137 kfree(buf);
138 return ret;
139}
140EXPORT_SYMBOL(scsi_partsize);
141
142/*
143 * Function : static int setsize(unsigned long capacity,unsigned int *cyls,
144 * unsigned int *hds, unsigned int *secs);
145 *
146 * Purpose : to determine a near-optimal int 0x13 mapping for a
147 * SCSI disk in terms of lost space of size capacity, storing
148 * the results in *cyls, *hds, and *secs.
149 *
150 * Returns : -1 on failure, 0 on success.
151 *
152 * Extracted from
153 *
154 * WORKING X3T9.2
155 * DRAFT 792D
156 * see http://www.t10.org/ftp/t10/drafts/cam/cam-r12b.pdf
157 *
158 * Revision 6
159 * 10-MAR-94
160 * Information technology -
161 * SCSI-2 Common access method
162 * transport and SCSI interface module
163 *
164 * ANNEX A :
165 *
166 * setsize() converts a read capacity value to int 13h
167 * head-cylinder-sector requirements. It minimizes the value for
168 * number of heads and maximizes the number of cylinders. This
169 * will support rather large disks before the number of heads
170 * will not fit in 4 bits (or 6 bits). This algorithm also
171 * minimizes the number of sectors that will be unused at the end
172 * of the disk while allowing for very large disks to be
173 * accommodated. This algorithm does not use physical geometry.
174 */
175
176static int setsize(unsigned long capacity, unsigned int *cyls, unsigned int *hds,
177 unsigned int *secs)
178{
179 unsigned int rv = 0;
180 unsigned long heads, sectors, cylinders, temp;
181
182 cylinders = 1024L; /* Set number of cylinders to max */
183 sectors = 62L; /* Maximize sectors per track */
184
185 temp = cylinders * sectors; /* Compute divisor for heads */
186 heads = capacity / temp; /* Compute value for number of heads */
187 if (capacity % temp) { /* If no remainder, done! */
188 heads++; /* Else, increment number of heads */
189 temp = cylinders * heads; /* Compute divisor for sectors */
190 sectors = capacity / temp; /* Compute value for sectors per
191 track */
192 if (capacity % temp) { /* If no remainder, done! */
193 sectors++; /* Else, increment number of sectors */
194 temp = heads * sectors; /* Compute divisor for cylinders */
195 cylinders = capacity / temp; /* Compute number of cylinders */
196 }
197 }
198 if (cylinders == 0)
199 rv = (unsigned) -1; /* Give error if 0 cylinders */
200
201 *cyls = (unsigned int) cylinders; /* Stuff return values */
202 *secs = (unsigned int) sectors;
203 *hds = (unsigned int) heads;
204 return (rv);
205}
206
207/**
208 * scsicam_bios_param - Determine geometry of a disk in cylinders/heads/sectors.
209 * @bdev: which device
210 * @capacity: size of the disk in sectors
211 * @ip: return value: ip[0]=heads, ip[1]=sectors, ip[2]=cylinders
212 *
213 * Description : determine the BIOS mapping/geometry used for a drive in a
214 * SCSI-CAM system, storing the results in ip as required
215 * by the HDIO_GETGEO ioctl().
216 *
217 * Returns : -1 on failure, 0 on success.
218 */
219int scsicam_bios_param(struct block_device *bdev, sector_t capacity, int *ip)
220{
221 u64 capacity64 = capacity; /* Suppress gcc warning */
222 int ret = 0;
223
224 /* try to infer mapping from partition table */
225 if (scsi_partsize(bdev, capacity, ip))
226 return 0;
227
228 if (capacity64 < (1ULL << 32)) {
229 /*
230 * Pick some standard mapping with at most 1024 cylinders, and
231 * at most 62 sectors per track - this works up to 7905 MB.
232 */
233 ret = setsize((unsigned long)capacity, (unsigned int *)ip + 2,
234 (unsigned int *)ip + 0, (unsigned int *)ip + 1);
235 }
236
237 /*
238 * If something went wrong, then apparently we have to return a geometry
239 * with more than 1024 cylinders.
240 */
241 if (ret || ip[0] > 255 || ip[1] > 63) {
242 if ((capacity >> 11) > 65534) {
243 ip[0] = 255;
244 ip[1] = 63;
245 } else {
246 ip[0] = 64;
247 ip[1] = 32;
248 }
249
250 if (capacity > 65535*63*255)
251 ip[2] = 65535;
252 else
253 ip[2] = (unsigned long)capacity / (ip[0] * ip[1]);
254 }
255
256 return 0;
257}
258EXPORT_SYMBOL(scsicam_bios_param);