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 unsigned char *scsi_bios_ptable(struct block_device *dev) 36 { 37 unsigned char *res = kmalloc(66, GFP_KERNEL); 38 if (res) { 39 struct block_device *bdev = dev->bd_contains; 40 Sector sect; 41 void *data = read_dev_sector(bdev, 0, §); 42 if (data) { 43 memcpy(res, data + 0x1be, 66); 44 put_dev_sector(sect); 45 } else { 46 kfree(res); 47 res = NULL; 48 } 49 } 50 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 unsigned char *p; 70 u64 capacity64 = capacity; /* Suppress gcc warning */ 71 int ret; 72 73 p = scsi_bios_ptable(bdev); 74 if (!p) 75 return -1; 76 77 /* try to infer mapping from partition table */ 78 ret = scsi_partsize(p, (unsigned long)capacity, (unsigned int *)ip + 2, 79 (unsigned int *)ip + 0, (unsigned int *)ip + 1); 80 kfree(p); 81 82 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 if (ret || ip[0] > 255 || ip[1] > 63) { 93 if ((capacity >> 11) > 65534) { 94 ip[0] = 255; 95 ip[1] = 63; 96 } else { 97 ip[0] = 64; 98 ip[1] = 32; 99 } 100 101 if (capacity > 65535*63*255) 102 ip[2] = 65535; 103 else 104 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 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 if (*(unsigned short *) (buf + 64) == 0xAA55) { 135 for (largest_cyl = -1, i = 0; i < 4; ++i, ++p) { 136 if (!p->sys_ind) 137 continue; 138 #ifdef DEBUG 139 printk("scsicam_bios_param : partition %d has system \n", 140 i); 141 #endif 142 cyl = p->cyl + ((p->sector & 0xc0) << 2); 143 if (cyl > largest_cyl) { 144 largest_cyl = cyl; 145 largest = p; 146 } 147 } 148 } 149 if (largest) { 150 end_cyl = largest->end_cyl + ((largest->end_sector & 0xc0) << 2); 151 end_head = largest->end_head; 152 end_sector = largest->end_sector & 0x3f; 153 154 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 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 logical_end = get_unaligned(&largest->start_sect) 167 + get_unaligned(&largest->nr_sects); 168 169 /* This is for >1023 cylinders */ 170 ext_cyl = (logical_end - (end_head * end_sector + end_sector)) 171 / (end_head + 1) / end_sector; 172 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 if ((logical_end == physical_end) || 181 (end_cyl == 1023 && ext_physical_end == logical_end)) { 182 *secs = end_sector; 183 *hds = end_head + 1; 184 *cyls = capacity / ((end_head + 1) * end_sector); 185 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 heads = capacity / temp; /* Compute value for number of heads */ 241 if (capacity % temp) { /* If no remainder, done! */ 242 heads++; /* Else, increment number of heads */ 243 temp = cylinders * heads; /* Compute divisor for sectors */ 244 sectors = capacity / temp; /* Compute value for sectors per 245 track */ 246 if (capacity % temp) { /* If no remainder, done! */ 247 sectors++; /* Else, increment number of sectors */ 248 temp = heads * sectors; /* Compute divisor for cylinders */ 249 cylinders = capacity / temp; /* Compute number of cylinders */ 250 } 251 } 252 if (cylinders == 0) 253 rv = (unsigned) -1; /* Give error if 0 cylinders */ 254 255 *cyls = (unsigned int) cylinders; /* Stuff return values */ 256 *secs = (unsigned int) sectors; 257 *hds = (unsigned int) heads; 258 return (rv); 259 } 260