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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 <linux/buffer_head.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 | unsigned char *scsi_bios_ptable(struct block_device *dev) |
37 | { |
38 | unsigned char *res = kmalloc(66, GFP_KERNEL); |
39 | if (res) { |
40 | struct block_device *bdev = dev->bd_contains; |
41 | Sector sect; |
42 | void *data = read_dev_sector(bdev, 0, §); |
43 | if (data) { |
44 | memcpy(res, data + 0x1be, 66); |
45 | put_dev_sector(sect); |
46 | } else { |
47 | kfree(res); |
48 | res = NULL; |
49 | } |
50 | } |
51 | 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 | 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 | p = scsi_bios_ptable(bdev); |
75 | if (!p) |
76 | return -1; |
77 | |
78 | /* try to infer mapping from partition table */ |
79 | ret = scsi_partsize(p, (unsigned long)capacity, (unsigned int *)ip + 2, |
80 | (unsigned int *)ip + 0, (unsigned int *)ip + 1); |
81 | kfree(p); |
82 | |
83 | 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 | if (ret || ip[0] > 255 || ip[1] > 63) { |
94 | if ((capacity >> 11) > 65534) { |
95 | ip[0] = 255; |
96 | ip[1] = 63; |
97 | } else { |
98 | ip[0] = 64; |
99 | ip[1] = 32; |
100 | } |
101 | |
102 | if (capacity > 65535*63*255) |
103 | ip[2] = 65535; |
104 | else |
105 | 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 | * Description: 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 | 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 | if (*(unsigned short *) (buf + 64) == 0xAA55) { |
136 | for (largest_cyl = -1, i = 0; i < 4; ++i, ++p) { |
137 | if (!p->sys_ind) |
138 | continue; |
139 | #ifdef DEBUG |
140 | printk("scsicam_bios_param : partition %d has system \n", |
141 | i); |
142 | #endif |
143 | cyl = p->cyl + ((p->sector & 0xc0) << 2); |
144 | if (cyl > largest_cyl) { |
145 | largest_cyl = cyl; |
146 | largest = p; |
147 | } |
148 | } |
149 | } |
150 | if (largest) { |
151 | end_cyl = largest->end_cyl + ((largest->end_sector & 0xc0) << 2); |
152 | end_head = largest->end_head; |
153 | end_sector = largest->end_sector & 0x3f; |
154 | |
155 | 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 | physical_end = end_cyl * (end_head + 1) * end_sector + |
164 | end_head * end_sector + end_sector; |
165 | |
166 | /* This is the actual _sector_ number at the end */ |
167 | logical_end = get_unaligned(&largest->start_sect) |
168 | + get_unaligned(&largest->nr_sects); |
169 | |
170 | /* This is for >1023 cylinders */ |
171 | ext_cyl = (logical_end - (end_head * end_sector + end_sector)) |
172 | / (end_head + 1) / end_sector; |
173 | ext_physical_end = ext_cyl * (end_head + 1) * end_sector + |
174 | 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 | if ((logical_end == physical_end) || |
182 | (end_cyl == 1023 && ext_physical_end == logical_end)) { |
183 | *secs = end_sector; |
184 | *hds = end_head + 1; |
185 | *cyls = capacity / ((end_head + 1) * end_sector); |
186 | 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 | heads = capacity / temp; /* Compute value for number of heads */ |
242 | if (capacity % temp) { /* If no remainder, done! */ |
243 | heads++; /* Else, increment number of heads */ |
244 | temp = cylinders * heads; /* Compute divisor for sectors */ |
245 | sectors = capacity / temp; /* Compute value for sectors per |
246 | track */ |
247 | if (capacity % temp) { /* If no remainder, done! */ |
248 | sectors++; /* Else, increment number of sectors */ |
249 | temp = heads * sectors; /* Compute divisor for cylinders */ |
250 | cylinders = capacity / temp; /* Compute number of cylinders */ |
251 | } |
252 | } |
253 | if (cylinders == 0) |
254 | rv = (unsigned) -1; /* Give error if 0 cylinders */ |
255 | |
256 | *cyls = (unsigned int) cylinders; /* Stuff return values */ |
257 | *secs = (unsigned int) sectors; |
258 | *hds = (unsigned int) heads; |
259 | return (rv); |
260 | } |
261 |
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