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