Branch data 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/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 : :
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 : 0 : unsigned char *scsi_bios_ptable(struct block_device *dev)
36 : : {
37 : : unsigned char *res = kmalloc(66, GFP_KERNEL);
38 [ # # ]: 0 : if (res) {
39 : 0 : struct block_device *bdev = dev->bd_contains;
40 : : Sector sect;
41 : 0 : void *data = read_dev_sector(bdev, 0, §);
42 [ # # ]: 0 : if (data) {
43 : 0 : memcpy(res, data + 0x1be, 66);
44 : : put_dev_sector(sect);
45 : : } else {
46 : 0 : kfree(res);
47 : : 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 : 0 : int 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 : 0 : p = scsi_bios_ptable(bdev);
74 [ # # ]: 0 : if (!p)
75 : : 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 : : 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 : : 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 : 0 : int 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 [ # # ]: 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 : : #ifdef DEBUG
139 : : printk("scsicam_bios_param : partition %d has system \n",
140 : : i);
141 : : #endif
142 : 0 : cyl = p->cyl + ((p->sector & 0xc0) << 2);
143 [ # # ]: 0 : if (cyl > largest_cyl) {
144 : : largest_cyl = cyl;
145 : : 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 : : 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 : 0 : 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 : 0 : / (end_head + 1) / end_sector;
172 : 0 : ext_physical_end = ext_cyl * (end_head + 1) * end_sector +
173 : 0 : 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 : 0 : (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 : : 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 : : 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 : 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 : : 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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