Line data Source code
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/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 :
24 : static 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 : */
35 : unsigned char *scsi_bios_ptable(struct block_device *dev)
36 : {
37 0 : unsigned char *res = kmalloc(66, GFP_KERNEL);
38 0 : if (res) {
39 0 : struct block_device *bdev = dev->bd_contains;
40 0 : Sector sect;
41 0 : void *data = read_dev_sector(bdev, 0, §);
42 0 : if (data) {
43 0 : memcpy(res, data + 0x1be, 66);
44 0 : put_dev_sector(sect);
45 : } else {
46 0 : kfree(res);
47 0 : res = NULL;
48 : }
49 : }
50 0 : return res;
51 : }
52 : EXPORT_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 :
67 : int scsicam_bios_param(struct block_device *bdev, sector_t capacity, int *ip)
68 : {
69 0 : unsigned char *p;
70 0 : u64 capacity64 = capacity; /* Suppress gcc warning */
71 0 : int ret;
72 :
73 0 : p = scsi_bios_ptable(bdev);
74 0 : if (!p)
75 0 : return -1;
76 :
77 : /* try to infer mapping from partition table */
78 0 : ret = scsi_partsize(p, (unsigned long)capacity, (unsigned int *)ip + 2,
79 : (unsigned int *)ip + 0, (unsigned int *)ip + 1);
80 0 : kfree(p);
81 :
82 0 : 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 0 : 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 0 : if (ret || ip[0] > 255 || ip[1] > 63) {
93 0 : if ((capacity >> 11) > 65534) {
94 0 : ip[0] = 255;
95 0 : ip[1] = 63;
96 : } else {
97 0 : ip[0] = 64;
98 0 : ip[1] = 32;
99 : }
100 :
101 0 : if (capacity > 65535*63*255)
102 0 : ip[2] = 65535;
103 : else
104 0 : ip[2] = (unsigned long)capacity / (ip[0] * ip[1]);
105 : }
106 :
107 0 : return 0;
108 : }
109 : EXPORT_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 :
125 : int scsi_partsize(unsigned char *buf, unsigned long capacity,
126 : unsigned int *cyls, unsigned int *hds, unsigned int *secs)
127 : {
128 0 : struct partition *p = (struct partition *)buf, *largest = NULL;
129 0 : int i, largest_cyl;
130 0 : int cyl, ext_cyl, end_head, end_cyl, end_sector;
131 0 : unsigned int logical_end, physical_end, ext_physical_end;
132 0 :
133 0 :
134 0 : if (*(unsigned short *) (buf + 64) == 0xAA55) {
135 0 : for (largest_cyl = -1, i = 0; i < 4; ++i, ++p) {
136 0 : if (!p->sys_ind)
137 0 : continue;
138 0 : #ifdef DEBUG
139 0 : printk("scsicam_bios_param : partition %d has system \n",
140 0 : i);
141 0 : #endif
142 0 : cyl = p->cyl + ((p->sector & 0xc0) << 2);
143 0 : if (cyl > largest_cyl) {
144 0 : largest_cyl = cyl;
145 0 : largest = p;
146 : }
147 : }
148 : }
149 0 : if (largest) {
150 0 : end_cyl = largest->end_cyl + ((largest->end_sector & 0xc0) << 2);
151 0 : end_head = largest->end_head;
152 0 : end_sector = largest->end_sector & 0x3f;
153 :
154 0 : if (end_head + 1 == 0 || end_sector == 0)
155 0 : 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 0 : 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 0 : logical_end = get_unaligned(&largest->start_sect)
167 : + get_unaligned(&largest->nr_sects);
168 :
169 : /* This is for >1023 cylinders */
170 0 : ext_cyl = (logical_end - (end_head * end_sector + end_sector))
171 : / (end_head + 1) / end_sector;
172 0 : 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 0 : if ((logical_end == physical_end) ||
181 : (end_cyl == 1023 && ext_physical_end == logical_end)) {
182 0 : *secs = end_sector;
183 0 : *hds = end_head + 1;
184 0 : *cyls = capacity / ((end_head + 1) * end_sector);
185 0 : 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 0 : return -1;
193 : }
194 : EXPORT_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 :
230 : static int setsize(unsigned long capacity, unsigned int *cyls, unsigned int *hds,
231 : unsigned int *secs)
232 : {
233 0 : unsigned int rv = 0;
234 0 : unsigned long heads, sectors, cylinders, temp;
235 0 :
236 0 : cylinders = 1024L; /* Set number of cylinders to max */
237 0 : sectors = 62L; /* Maximize sectors per track */
238 :
239 0 : temp = cylinders * sectors; /* Compute divisor for heads */
240 0 : heads = capacity / temp; /* Compute value for number of heads */
241 0 : if (capacity % temp) { /* If no remainder, done! */
242 0 : heads++; /* Else, increment number of heads */
243 0 : temp = cylinders * heads; /* Compute divisor for sectors */
244 0 : sectors = capacity / temp; /* Compute value for sectors per
245 : track */
246 0 : if (capacity % temp) { /* If no remainder, done! */
247 0 : sectors++; /* Else, increment number of sectors */
248 0 : temp = heads * sectors; /* Compute divisor for cylinders */
249 0 : cylinders = capacity / temp; /* Compute number of cylinders */
250 : }
251 : }
252 0 : if (cylinders == 0)
253 0 : rv = (unsigned) -1; /* Give error if 0 cylinders */
254 :
255 0 : *cyls = (unsigned int) cylinders; /* Stuff return values */
256 0 : *secs = (unsigned int) sectors;
257 0 : *hds = (unsigned int) heads;
258 0 : return (rv);
259 : }
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