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 unsigned char *scsi_bios_ptable(struct block_device *dev) 28 { 29 unsigned char *res = kmalloc(66, GFP_KERNEL); 30 if (res) { 31 struct block_device *bdev = dev->bd_contains; 32 Sector sect; 33 void *data = read_dev_sector(bdev, 0, §); 34 if (data) { 35 memcpy(res, data + 0x1be, 66); 36 put_dev_sector(sect); 37 } else { 38 kfree(res); 39 res = NULL; 40 } 41 } 42 return res; 43 } 44 EXPORT_SYMBOL(scsi_bios_ptable); 45 46 /* 47 * Function : int scsicam_bios_param (struct block_device *bdev, ector_t capacity, int *ip) 48 * 49 * Purpose : to determine the BIOS mapping used for a drive in a 50 * SCSI-CAM system, storing the results in ip as required 51 * by the HDIO_GETGEO ioctl(). 52 * 53 * Returns : -1 on failure, 0 on success. 54 * 55 */ 56 57 int scsicam_bios_param(struct block_device *bdev, sector_t capacity, int *ip) 58 { 59 unsigned char *p; 60 u64 capacity64 = capacity; /* Suppress gcc warning */ 61 int ret; 62 63 p = scsi_bios_ptable(bdev); 64 if (!p) 65 return -1; 66 67 /* try to infer mapping from partition table */ 68 ret = scsi_partsize(p, (unsigned long)capacity, (unsigned int *)ip + 2, 69 (unsigned int *)ip + 0, (unsigned int *)ip + 1); 70 kfree(p); 71 72 if (ret == -1 && capacity64 < (1ULL << 32)) { 73 /* pick some standard mapping with at most 1024 cylinders, 74 and at most 62 sectors per track - this works up to 75 7905 MB */ 76 ret = setsize((unsigned long)capacity, (unsigned int *)ip + 2, 77 (unsigned int *)ip + 0, (unsigned int *)ip + 1); 78 } 79 80 /* if something went wrong, then apparently we have to return 81 a geometry with more than 1024 cylinders */ 82 if (ret || ip[0] > 255 || ip[1] > 63) { 83 if ((capacity >> 11) > 65534) { 84 ip[0] = 255; 85 ip[1] = 63; 86 } else { 87 ip[0] = 64; 88 ip[1] = 32; 89 } 90 91 if (capacity > 65535*63*255) 92 ip[2] = 65535; 93 else 94 ip[2] = (unsigned long)capacity / (ip[0] * ip[1]); 95 } 96 97 return 0; 98 } 99 EXPORT_SYMBOL(scsicam_bios_param); 100 101 /* 102 * Function : static int scsi_partsize(unsigned char *buf, unsigned long 103 * capacity,unsigned int *cyls, unsigned int *hds, unsigned int *secs); 104 * 105 * Purpose : to determine the BIOS mapping used to create the partition 106 * table, storing the results in *cyls, *hds, and *secs 107 * 108 * Returns : -1 on failure, 0 on success. 109 * 110 */ 111 112 int scsi_partsize(unsigned char *buf, unsigned long capacity, 113 unsigned int *cyls, unsigned int *hds, unsigned int *secs) 114 { 115 struct partition *p = (struct partition *)buf, *largest = NULL; 116 int i, largest_cyl; 117 int cyl, ext_cyl, end_head, end_cyl, end_sector; 118 unsigned int logical_end, physical_end, ext_physical_end; 119 120 121 if (*(unsigned short *) (buf + 64) == 0xAA55) { 122 for (largest_cyl = -1, i = 0; i < 4; ++i, ++p) { 123 if (!p->sys_ind) 124 continue; 125 #ifdef DEBUG 126 printk("scsicam_bios_param : partition %d has system \n", 127 i); 128 #endif 129 cyl = p->cyl + ((p->sector & 0xc0) << 2); 130 if (cyl > largest_cyl) { 131 largest_cyl = cyl; 132 largest = p; 133 } 134 } 135 } 136 if (largest) { 137 end_cyl = largest->end_cyl + ((largest->end_sector & 0xc0) << 2); 138 end_head = largest->end_head; 139 end_sector = largest->end_sector & 0x3f; 140 141 if (end_head + 1 == 0 || end_sector == 0) 142 return -1; 143 144 #ifdef DEBUG 145 printk("scsicam_bios_param : end at h = %d, c = %d, s = %d\n", 146 end_head, end_cyl, end_sector); 147 #endif 148 149 physical_end = end_cyl * (end_head + 1) * end_sector + 150 end_head * end_sector + end_sector; 151 152 /* This is the actual _sector_ number at the end */ 153 logical_end = get_unaligned(&largest->start_sect) 154 + get_unaligned(&largest->nr_sects); 155 156 /* This is for >1023 cylinders */ 157 ext_cyl = (logical_end - (end_head * end_sector + end_sector)) 158 / (end_head + 1) / end_sector; 159 ext_physical_end = ext_cyl * (end_head + 1) * end_sector + 160 end_head * end_sector + end_sector; 161 162 #ifdef DEBUG 163 printk("scsicam_bios_param : logical_end=%d physical_end=%d ext_physical_end=%d ext_cyl=%d\n" 164 ,logical_end, physical_end, ext_physical_end, ext_cyl); 165 #endif 166 167 if ((logical_end == physical_end) || 168 (end_cyl == 1023 && ext_physical_end == logical_end)) { 169 *secs = end_sector; 170 *hds = end_head + 1; 171 *cyls = capacity / ((end_head + 1) * end_sector); 172 return 0; 173 } 174 #ifdef DEBUG 175 printk("scsicam_bios_param : logical (%u) != physical (%u)\n", 176 logical_end, physical_end); 177 #endif 178 } 179 return -1; 180 } 181 EXPORT_SYMBOL(scsi_partsize); 182 183 /* 184 * Function : static int setsize(unsigned long capacity,unsigned int *cyls, 185 * unsigned int *hds, unsigned int *secs); 186 * 187 * Purpose : to determine a near-optimal int 0x13 mapping for a 188 * SCSI disk in terms of lost space of size capacity, storing 189 * the results in *cyls, *hds, and *secs. 190 * 191 * Returns : -1 on failure, 0 on success. 192 * 193 * Extracted from 194 * 195 * WORKING X3T9.2 196 * DRAFT 792D 197 * 198 * 199 * Revision 6 200 * 10-MAR-94 201 * Information technology - 202 * SCSI-2 Common access method 203 * transport and SCSI interface module 204 * 205 * ANNEX A : 206 * 207 * setsize() converts a read capacity value to int 13h 208 * head-cylinder-sector requirements. It minimizes the value for 209 * number of heads and maximizes the number of cylinders. This 210 * will support rather large disks before the number of heads 211 * will not fit in 4 bits (or 6 bits). This algorithm also 212 * minimizes the number of sectors that will be unused at the end 213 * of the disk while allowing for very large disks to be 214 * accommodated. This algorithm does not use physical geometry. 215 */ 216 217 static int setsize(unsigned long capacity, unsigned int *cyls, unsigned int *hds, 218 unsigned int *secs) 219 { 220 unsigned int rv = 0; 221 unsigned long heads, sectors, cylinders, temp; 222 223 cylinders = 1024L; /* Set number of cylinders to max */ 224 sectors = 62L; /* Maximize sectors per track */ 225 226 temp = cylinders * sectors; /* Compute divisor for heads */ 227 heads = capacity / temp; /* Compute value for number of heads */ 228 if (capacity % temp) { /* If no remainder, done! */ 229 heads++; /* Else, increment number of heads */ 230 temp = cylinders * heads; /* Compute divisor for sectors */ 231 sectors = capacity / temp; /* Compute value for sectors per 232 track */ 233 if (capacity % temp) { /* If no remainder, done! */ 234 sectors++; /* Else, increment number of sectors */ 235 temp = heads * sectors; /* Compute divisor for cylinders */ 236 cylinders = capacity / temp; /* Compute number of cylinders */ 237 } 238 } 239 if (cylinders == 0) 240 rv = (unsigned) -1; /* Give error if 0 cylinders */ 241 242 *cyls = (unsigned int) cylinders; /* Stuff return values */ 243 *secs = (unsigned int) sectors; 244 *hds = (unsigned int) heads; 245 return (rv); 246 } 247