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b2441318 | 1 | // SPDX-License-Identifier: GPL-2.0 |
1da177e4 LT |
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> | |
5a0e3ad6 | 15 | #include <linux/slab.h> |
1da177e4 | 16 | #include <linux/fs.h> |
1da177e4 LT |
17 | #include <linux/kernel.h> |
18 | #include <linux/blkdev.h> | |
4ee60ec1 | 19 | #include <linux/pagemap.h> |
1442f76d | 20 | #include <linux/msdos_partition.h> |
1da177e4 LT |
21 | #include <asm/unaligned.h> |
22 | ||
23 | #include <scsi/scsicam.h> | |
24 | ||
eb44820c RL |
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 | */ | |
1da177e4 LT |
33 | unsigned char *scsi_bios_ptable(struct block_device *dev) |
34 | { | |
a954ea81 | 35 | struct address_space *mapping = bdev_whole(dev)->bd_inode->i_mapping; |
e63105df | 36 | unsigned char *res = NULL; |
5fb9bfe0 | 37 | struct folio *folio; |
e63105df | 38 | |
5fb9bfe0 MWO |
39 | folio = read_mapping_folio(mapping, 0, NULL); |
40 | if (IS_ERR(folio)) | |
e63105df CH |
41 | return NULL; |
42 | ||
5fb9bfe0 MWO |
43 | res = kmemdup(folio_address(folio) + 0x1be, 66, GFP_KERNEL); |
44 | folio_put(folio); | |
1da177e4 LT |
45 | return res; |
46 | } | |
47 | EXPORT_SYMBOL(scsi_bios_ptable); | |
48 | ||
eb44820c RL |
49 | /** |
50 | * scsi_partsize - Parse cylinders/heads/sectors from PC partition table | |
a10183d7 | 51 | * @bdev: block device to parse |
eb44820c | 52 | * @capacity: size of the disk in sectors |
a10183d7 | 53 | * @geom: output in form of [hds, cylinders, sectors] |
1da177e4 | 54 | * |
739aca06 | 55 | * Determine the BIOS mapping/geometry used to create the partition |
a10183d7 | 56 | * table, storing the results in @geom. |
1da177e4 | 57 | * |
a10183d7 | 58 | * Returns: %false on failure, %true on success. |
1da177e4 | 59 | */ |
a10183d7 | 60 | bool scsi_partsize(struct block_device *bdev, sector_t capacity, int geom[3]) |
1da177e4 | 61 | { |
1da177e4 LT |
62 | int cyl, ext_cyl, end_head, end_cyl, end_sector; |
63 | unsigned int logical_end, physical_end, ext_physical_end; | |
1442f76d | 64 | struct msdos_partition *p, *largest = NULL; |
a10183d7 CH |
65 | void *buf; |
66 | int ret = false; | |
1da177e4 | 67 | |
a10183d7 CH |
68 | buf = scsi_bios_ptable(bdev); |
69 | if (!buf) | |
70 | return false; | |
1da177e4 LT |
71 | |
72 | if (*(unsigned short *) (buf + 64) == 0xAA55) { | |
a10183d7 CH |
73 | int largest_cyl = -1, i; |
74 | ||
75 | for (i = 0, p = buf; i < 4; i++, p++) { | |
1da177e4 LT |
76 | if (!p->sys_ind) |
77 | continue; | |
78 | #ifdef DEBUG | |
79 | printk("scsicam_bios_param : partition %d has system \n", | |
80 | i); | |
81 | #endif | |
82 | cyl = p->cyl + ((p->sector & 0xc0) << 2); | |
83 | if (cyl > largest_cyl) { | |
84 | largest_cyl = cyl; | |
85 | largest = p; | |
86 | } | |
87 | } | |
88 | } | |
89 | if (largest) { | |
90 | end_cyl = largest->end_cyl + ((largest->end_sector & 0xc0) << 2); | |
91 | end_head = largest->end_head; | |
92 | end_sector = largest->end_sector & 0x3f; | |
93 | ||
94 | if (end_head + 1 == 0 || end_sector == 0) | |
a10183d7 | 95 | goto out_free_buf; |
1da177e4 LT |
96 | |
97 | #ifdef DEBUG | |
98 | printk("scsicam_bios_param : end at h = %d, c = %d, s = %d\n", | |
99 | end_head, end_cyl, end_sector); | |
100 | #endif | |
101 | ||
102 | physical_end = end_cyl * (end_head + 1) * end_sector + | |
103 | end_head * end_sector + end_sector; | |
104 | ||
105 | /* This is the actual _sector_ number at the end */ | |
678e2757 CH |
106 | logical_end = get_unaligned_le32(&largest->start_sect) |
107 | + get_unaligned_le32(&largest->nr_sects); | |
1da177e4 LT |
108 | |
109 | /* This is for >1023 cylinders */ | |
110 | ext_cyl = (logical_end - (end_head * end_sector + end_sector)) | |
111 | / (end_head + 1) / end_sector; | |
112 | ext_physical_end = ext_cyl * (end_head + 1) * end_sector + | |
113 | end_head * end_sector + end_sector; | |
114 | ||
115 | #ifdef DEBUG | |
116 | printk("scsicam_bios_param : logical_end=%d physical_end=%d ext_physical_end=%d ext_cyl=%d\n" | |
117 | ,logical_end, physical_end, ext_physical_end, ext_cyl); | |
118 | #endif | |
119 | ||
a10183d7 CH |
120 | if (logical_end == physical_end || |
121 | (end_cyl == 1023 && ext_physical_end == logical_end)) { | |
122 | geom[0] = end_head + 1; | |
123 | geom[1] = end_sector; | |
124 | geom[2] = (unsigned long)capacity / | |
125 | ((end_head + 1) * end_sector); | |
126 | ret = true; | |
127 | goto out_free_buf; | |
1da177e4 LT |
128 | } |
129 | #ifdef DEBUG | |
130 | printk("scsicam_bios_param : logical (%u) != physical (%u)\n", | |
131 | logical_end, physical_end); | |
132 | #endif | |
133 | } | |
a10183d7 CH |
134 | |
135 | out_free_buf: | |
136 | kfree(buf); | |
137 | return ret; | |
1da177e4 LT |
138 | } |
139 | EXPORT_SYMBOL(scsi_partsize); | |
140 | ||
141 | /* | |
142 | * Function : static int setsize(unsigned long capacity,unsigned int *cyls, | |
143 | * unsigned int *hds, unsigned int *secs); | |
144 | * | |
145 | * Purpose : to determine a near-optimal int 0x13 mapping for a | |
146 | * SCSI disk in terms of lost space of size capacity, storing | |
147 | * the results in *cyls, *hds, and *secs. | |
148 | * | |
149 | * Returns : -1 on failure, 0 on success. | |
150 | * | |
151 | * Extracted from | |
152 | * | |
153 | * WORKING X3T9.2 | |
154 | * DRAFT 792D | |
eb44820c | 155 | * see http://www.t10.org/ftp/t10/drafts/cam/cam-r12b.pdf |
1da177e4 LT |
156 | * |
157 | * Revision 6 | |
158 | * 10-MAR-94 | |
159 | * Information technology - | |
160 | * SCSI-2 Common access method | |
161 | * transport and SCSI interface module | |
162 | * | |
163 | * ANNEX A : | |
164 | * | |
165 | * setsize() converts a read capacity value to int 13h | |
166 | * head-cylinder-sector requirements. It minimizes the value for | |
167 | * number of heads and maximizes the number of cylinders. This | |
168 | * will support rather large disks before the number of heads | |
169 | * will not fit in 4 bits (or 6 bits). This algorithm also | |
170 | * minimizes the number of sectors that will be unused at the end | |
171 | * of the disk while allowing for very large disks to be | |
172 | * accommodated. This algorithm does not use physical geometry. | |
173 | */ | |
174 | ||
175 | static int setsize(unsigned long capacity, unsigned int *cyls, unsigned int *hds, | |
176 | unsigned int *secs) | |
177 | { | |
178 | unsigned int rv = 0; | |
179 | unsigned long heads, sectors, cylinders, temp; | |
180 | ||
181 | cylinders = 1024L; /* Set number of cylinders to max */ | |
182 | sectors = 62L; /* Maximize sectors per track */ | |
183 | ||
184 | temp = cylinders * sectors; /* Compute divisor for heads */ | |
185 | heads = capacity / temp; /* Compute value for number of heads */ | |
186 | if (capacity % temp) { /* If no remainder, done! */ | |
187 | heads++; /* Else, increment number of heads */ | |
188 | temp = cylinders * heads; /* Compute divisor for sectors */ | |
189 | sectors = capacity / temp; /* Compute value for sectors per | |
190 | track */ | |
191 | if (capacity % temp) { /* If no remainder, done! */ | |
192 | sectors++; /* Else, increment number of sectors */ | |
193 | temp = heads * sectors; /* Compute divisor for cylinders */ | |
194 | cylinders = capacity / temp; /* Compute number of cylinders */ | |
195 | } | |
196 | } | |
197 | if (cylinders == 0) | |
198 | rv = (unsigned) -1; /* Give error if 0 cylinders */ | |
199 | ||
200 | *cyls = (unsigned int) cylinders; /* Stuff return values */ | |
201 | *secs = (unsigned int) sectors; | |
202 | *hds = (unsigned int) heads; | |
203 | return (rv); | |
204 | } | |
26ae3533 CH |
205 | |
206 | /** | |
207 | * scsicam_bios_param - Determine geometry of a disk in cylinders/heads/sectors. | |
208 | * @bdev: which device | |
209 | * @capacity: size of the disk in sectors | |
210 | * @ip: return value: ip[0]=heads, ip[1]=sectors, ip[2]=cylinders | |
211 | * | |
212 | * Description : determine the BIOS mapping/geometry used for a drive in a | |
213 | * SCSI-CAM system, storing the results in ip as required | |
214 | * by the HDIO_GETGEO ioctl(). | |
215 | * | |
216 | * Returns : -1 on failure, 0 on success. | |
217 | */ | |
218 | int scsicam_bios_param(struct block_device *bdev, sector_t capacity, int *ip) | |
219 | { | |
26ae3533 | 220 | u64 capacity64 = capacity; /* Suppress gcc warning */ |
a10183d7 | 221 | int ret = 0; |
26ae3533 CH |
222 | |
223 | /* try to infer mapping from partition table */ | |
a10183d7 CH |
224 | if (scsi_partsize(bdev, capacity, ip)) |
225 | return 0; | |
26ae3533 | 226 | |
a10183d7 | 227 | if (capacity64 < (1ULL << 32)) { |
26ae3533 CH |
228 | /* |
229 | * Pick some standard mapping with at most 1024 cylinders, and | |
230 | * at most 62 sectors per track - this works up to 7905 MB. | |
231 | */ | |
232 | ret = setsize((unsigned long)capacity, (unsigned int *)ip + 2, | |
233 | (unsigned int *)ip + 0, (unsigned int *)ip + 1); | |
234 | } | |
235 | ||
236 | /* | |
237 | * If something went wrong, then apparently we have to return a geometry | |
238 | * with more than 1024 cylinders. | |
239 | */ | |
240 | if (ret || ip[0] > 255 || ip[1] > 63) { | |
241 | if ((capacity >> 11) > 65534) { | |
242 | ip[0] = 255; | |
243 | ip[1] = 63; | |
244 | } else { | |
245 | ip[0] = 64; | |
246 | ip[1] = 32; | |
247 | } | |
248 | ||
249 | if (capacity > 65535*63*255) | |
250 | ip[2] = 65535; | |
251 | else | |
252 | ip[2] = (unsigned long)capacity / (ip[0] * ip[1]); | |
253 | } | |
254 | ||
255 | return 0; | |
256 | } | |
257 | EXPORT_SYMBOL(scsicam_bios_param); |