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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 <asm/unaligned.h>
21 : :
22 : : #include <scsi/scsicam.h>
23 : :
24 : :
25 : : static int setsize(unsigned long capacity, unsigned int *cyls, unsigned int *hds,
26 : : unsigned int *secs);
27 : :
28 : : /**
29 : : * scsi_bios_ptable - Read PC partition table out of first sector of device.
30 : : * @dev: from this device
31 : : *
32 : : * Description: Reads the first sector from the device and returns %0x42 bytes
33 : : * starting at offset %0x1be.
34 : : * Returns: partition table in kmalloc(GFP_KERNEL) memory, or NULL on error.
35 : : */
36 : 0 : unsigned char *scsi_bios_ptable(struct block_device *dev)
37 : : {
38 : : unsigned char *res = kmalloc(66, GFP_KERNEL);
39 [ # # ]: 0 : if (res) {
40 : 0 : struct block_device *bdev = dev->bd_contains;
41 : : Sector sect;
42 : 0 : void *data = read_dev_sector(bdev, 0, §);
43 [ # # ]: 0 : if (data) {
44 : 0 : memcpy(res, data + 0x1be, 66);
45 : : put_dev_sector(sect);
46 : : } else {
47 : 0 : kfree(res);
48 : : res = NULL;
49 : : }
50 : : }
51 : 0 : return res;
52 : : }
53 : : EXPORT_SYMBOL(scsi_bios_ptable);
54 : :
55 : : /**
56 : : * scsicam_bios_param - Determine geometry of a disk in cylinders/heads/sectors.
57 : : * @bdev: which device
58 : : * @capacity: size of the disk in sectors
59 : : * @ip: return value: ip[0]=heads, ip[1]=sectors, ip[2]=cylinders
60 : : *
61 : : * Description : determine the BIOS mapping/geometry used for a drive in a
62 : : * SCSI-CAM system, storing the results in ip as required
63 : : * by the HDIO_GETGEO ioctl().
64 : : *
65 : : * Returns : -1 on failure, 0 on success.
66 : : */
67 : :
68 : 0 : int scsicam_bios_param(struct block_device *bdev, sector_t capacity, int *ip)
69 : : {
70 : : unsigned char *p;
71 : : u64 capacity64 = capacity; /* Suppress gcc warning */
72 : : int ret;
73 : :
74 : 0 : p = scsi_bios_ptable(bdev);
75 [ # # ]: 0 : if (!p)
76 : : return -1;
77 : :
78 : : /* try to infer mapping from partition table */
79 : 0 : ret = scsi_partsize(p, (unsigned long)capacity, (unsigned int *)ip + 2,
80 : : (unsigned int *)ip + 0, (unsigned int *)ip + 1);
81 : 0 : kfree(p);
82 : :
83 [ # # ]: 0 : if (ret == -1 && capacity64 < (1ULL << 32)) {
84 : : /* pick some standard mapping with at most 1024 cylinders,
85 : : and at most 62 sectors per track - this works up to
86 : : 7905 MB */
87 : : ret = setsize((unsigned long)capacity, (unsigned int *)ip + 2,
88 : : (unsigned int *)ip + 0, (unsigned int *)ip + 1);
89 : : }
90 : :
91 : : /* if something went wrong, then apparently we have to return
92 : : a geometry with more than 1024 cylinders */
93 [ # # # # : 0 : if (ret || ip[0] > 255 || ip[1] > 63) {
# # ]
94 [ # # ]: 0 : if ((capacity >> 11) > 65534) {
95 : 0 : ip[0] = 255;
96 : 0 : ip[1] = 63;
97 : : } else {
98 : 0 : ip[0] = 64;
99 : 0 : ip[1] = 32;
100 : : }
101 : :
102 [ # # ]: 0 : if (capacity > 65535*63*255)
103 : 0 : ip[2] = 65535;
104 : : else
105 : 0 : ip[2] = (unsigned long)capacity / (ip[0] * ip[1]);
106 : : }
107 : :
108 : : return 0;
109 : : }
110 : : EXPORT_SYMBOL(scsicam_bios_param);
111 : :
112 : : /**
113 : : * scsi_partsize - Parse cylinders/heads/sectors from PC partition table
114 : : * @buf: partition table, see scsi_bios_ptable()
115 : : * @capacity: size of the disk in sectors
116 : : * @cyls: put cylinders here
117 : : * @hds: put heads here
118 : : * @secs: put sectors here
119 : : *
120 : : * Determine the BIOS mapping/geometry used to create the partition
121 : : * table, storing the results in @cyls, @hds, and @secs
122 : : *
123 : : * Returns: -1 on failure, 0 on success.
124 : : */
125 : :
126 : 0 : int scsi_partsize(unsigned char *buf, unsigned long capacity,
127 : : unsigned int *cyls, unsigned int *hds, unsigned int *secs)
128 : : {
129 : : struct partition *p = (struct partition *)buf, *largest = NULL;
130 : : int i, largest_cyl;
131 : : int cyl, ext_cyl, end_head, end_cyl, end_sector;
132 : : unsigned int logical_end, physical_end, ext_physical_end;
133 : :
134 : :
135 [ # # ]: 0 : if (*(unsigned short *) (buf + 64) == 0xAA55) {
136 [ # # ]: 0 : for (largest_cyl = -1, i = 0; i < 4; ++i, ++p) {
137 [ # # ]: 0 : if (!p->sys_ind)
138 : 0 : continue;
139 : : #ifdef DEBUG
140 : : printk("scsicam_bios_param : partition %d has system \n",
141 : : i);
142 : : #endif
143 : 0 : cyl = p->cyl + ((p->sector & 0xc0) << 2);
144 [ # # ]: 0 : if (cyl > largest_cyl) {
145 : : largest_cyl = cyl;
146 : : largest = p;
147 : : }
148 : : }
149 : : }
150 [ # # ]: 0 : if (largest) {
151 : 0 : end_cyl = largest->end_cyl + ((largest->end_sector & 0xc0) << 2);
152 : 0 : end_head = largest->end_head;
153 : 0 : end_sector = largest->end_sector & 0x3f;
154 : :
155 [ # # ]: 0 : if (end_head + 1 == 0 || end_sector == 0)
156 : : return -1;
157 : :
158 : : #ifdef DEBUG
159 : : printk("scsicam_bios_param : end at h = %d, c = %d, s = %d\n",
160 : : end_head, end_cyl, end_sector);
161 : : #endif
162 : :
163 : 0 : physical_end = end_cyl * (end_head + 1) * end_sector +
164 : 0 : end_head * end_sector + end_sector;
165 : :
166 : : /* This is the actual _sector_ number at the end */
167 : 0 : logical_end = get_unaligned_le32(&largest->start_sect)
168 : : + get_unaligned_le32(&largest->nr_sects);
169 : :
170 : : /* This is for >1023 cylinders */
171 : 0 : ext_cyl = (logical_end - (end_head * end_sector + end_sector))
172 : 0 : / (end_head + 1) / end_sector;
173 : 0 : ext_physical_end = ext_cyl * (end_head + 1) * end_sector +
174 : 0 : end_head * end_sector + end_sector;
175 : :
176 : : #ifdef DEBUG
177 : : printk("scsicam_bios_param : logical_end=%d physical_end=%d ext_physical_end=%d ext_cyl=%d\n"
178 : : ,logical_end, physical_end, ext_physical_end, ext_cyl);
179 : : #endif
180 : :
181 [ # # # # ]: 0 : if ((logical_end == physical_end) ||
182 : 0 : (end_cyl == 1023 && ext_physical_end == logical_end)) {
183 : 0 : *secs = end_sector;
184 : 0 : *hds = end_head + 1;
185 : 0 : *cyls = capacity / ((end_head + 1) * end_sector);
186 : 0 : return 0;
187 : : }
188 : : #ifdef DEBUG
189 : : printk("scsicam_bios_param : logical (%u) != physical (%u)\n",
190 : : logical_end, physical_end);
191 : : #endif
192 : : }
193 : : return -1;
194 : : }
195 : : EXPORT_SYMBOL(scsi_partsize);
196 : :
197 : : /*
198 : : * Function : static int setsize(unsigned long capacity,unsigned int *cyls,
199 : : * unsigned int *hds, unsigned int *secs);
200 : : *
201 : : * Purpose : to determine a near-optimal int 0x13 mapping for a
202 : : * SCSI disk in terms of lost space of size capacity, storing
203 : : * the results in *cyls, *hds, and *secs.
204 : : *
205 : : * Returns : -1 on failure, 0 on success.
206 : : *
207 : : * Extracted from
208 : : *
209 : : * WORKING X3T9.2
210 : : * DRAFT 792D
211 : : * see http://www.t10.org/ftp/t10/drafts/cam/cam-r12b.pdf
212 : : *
213 : : * Revision 6
214 : : * 10-MAR-94
215 : : * Information technology -
216 : : * SCSI-2 Common access method
217 : : * transport and SCSI interface module
218 : : *
219 : : * ANNEX A :
220 : : *
221 : : * setsize() converts a read capacity value to int 13h
222 : : * head-cylinder-sector requirements. It minimizes the value for
223 : : * number of heads and maximizes the number of cylinders. This
224 : : * will support rather large disks before the number of heads
225 : : * will not fit in 4 bits (or 6 bits). This algorithm also
226 : : * minimizes the number of sectors that will be unused at the end
227 : : * of the disk while allowing for very large disks to be
228 : : * accommodated. This algorithm does not use physical geometry.
229 : : */
230 : :
231 : : static int setsize(unsigned long capacity, unsigned int *cyls, unsigned int *hds,
232 : : unsigned int *secs)
233 : : {
234 : : unsigned int rv = 0;
235 : : unsigned long heads, sectors, cylinders, temp;
236 : :
237 : : cylinders = 1024L; /* Set number of cylinders to max */
238 : : sectors = 62L; /* Maximize sectors per track */
239 : :
240 : : temp = cylinders * sectors; /* Compute divisor for heads */
241 : 0 : heads = capacity / temp; /* Compute value for number of heads */
242 [ # # ]: 0 : if (capacity % temp) { /* If no remainder, done! */
243 : 0 : heads++; /* Else, increment number of heads */
244 : 0 : temp = cylinders * heads; /* Compute divisor for sectors */
245 : 0 : sectors = capacity / temp; /* Compute value for sectors per
246 : : track */
247 [ # # ]: 0 : if (capacity % temp) { /* If no remainder, done! */
248 : 0 : sectors++; /* Else, increment number of sectors */
249 : 0 : temp = heads * sectors; /* Compute divisor for cylinders */
250 : 0 : cylinders = capacity / temp; /* Compute number of cylinders */
251 : : }
252 : : }
253 [ # # ]: 0 : if (cylinders == 0)
254 : : rv = (unsigned) -1; /* Give error if 0 cylinders */
255 : :
256 : 0 : *cyls = (unsigned int) cylinders; /* Stuff return values */
257 : 0 : *secs = (unsigned int) sectors;
258 : 0 : *hds = (unsigned int) heads;
259 : 0 : return (rv);
260 : : }
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