2 * scsicam.c - SCSI CAM support functions, use for HDIO_GETGEO, etc.
4 * Copyright 1993, 1994 Drew Eckhardt
6 * (Unix and Linux consulting and custom programming)
10 * For more information, please consult the SCSI-CAM draft.
13 #include <linux/module.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>
21 #include <scsi/scsicam.h>
24 static int setsize(unsigned long capacity, unsigned int *cyls, unsigned int *hds,
27 unsigned char *scsi_bios_ptable(struct block_device *dev)
29 unsigned char *res = kmalloc(66, GFP_KERNEL);
31 struct block_device *bdev = dev->bd_contains;
33 void *data = read_dev_sector(bdev, 0, §);
35 memcpy(res, data + 0x1be, 66);
44 EXPORT_SYMBOL(scsi_bios_ptable);
47 * Function : int scsicam_bios_param (struct block_device *bdev, ector_t capacity, int *ip)
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().
53 * Returns : -1 on failure, 0 on success.
57 int scsicam_bios_param(struct block_device *bdev, sector_t capacity, int *ip)
62 /* Are we above the max. allowed for cylinder/sector/head? */
63 if (capacity > 65535*63*255) {
71 p = scsi_bios_ptable(bdev);
75 /* try to infer mapping from partition table */
76 ret = scsi_partsize(p, (unsigned long)capacity, (unsigned int *)ip + 2,
77 (unsigned int *)ip + 0, (unsigned int *)ip + 1);
81 /* pick some standard mapping with at most 1024 cylinders,
82 and at most 62 sectors per track - this works up to
84 ret = setsize((unsigned long)capacity, (unsigned int *)ip + 2,
85 (unsigned int *)ip + 0, (unsigned int *)ip + 1);
88 /* if something went wrong, then apparently we have to return
89 a geometry with more than 1024 cylinders */
90 if (ret || ip[0] > 255 || ip[1] > 63) {
91 if ((capacity >> 11) > 65534) {
98 ip[2] = (unsigned long)capacity / (ip[0] * ip[1]);
103 EXPORT_SYMBOL(scsicam_bios_param);
106 * Function : static int scsi_partsize(unsigned char *buf, unsigned long
107 * capacity,unsigned int *cyls, unsigned int *hds, unsigned int *secs);
109 * Purpose : to determine the BIOS mapping used to create the partition
110 * table, storing the results in *cyls, *hds, and *secs
112 * Returns : -1 on failure, 0 on success.
116 int scsi_partsize(unsigned char *buf, unsigned long capacity,
117 unsigned int *cyls, unsigned int *hds, unsigned int *secs)
119 struct partition *p = (struct partition *)buf, *largest = NULL;
121 int cyl, ext_cyl, end_head, end_cyl, end_sector;
122 unsigned int logical_end, physical_end, ext_physical_end;
125 if (*(unsigned short *) (buf + 64) == 0xAA55) {
126 for (largest_cyl = -1, i = 0; i < 4; ++i, ++p) {
130 printk("scsicam_bios_param : partition %d has system \n",
133 cyl = p->cyl + ((p->sector & 0xc0) << 2);
134 if (cyl > largest_cyl) {
141 end_cyl = largest->end_cyl + ((largest->end_sector & 0xc0) << 2);
142 end_head = largest->end_head;
143 end_sector = largest->end_sector & 0x3f;
145 if (end_head + 1 == 0 || end_sector == 0)
149 printk("scsicam_bios_param : end at h = %d, c = %d, s = %d\n",
150 end_head, end_cyl, end_sector);
153 physical_end = end_cyl * (end_head + 1) * end_sector +
154 end_head * end_sector + end_sector;
156 /* This is the actual _sector_ number at the end */
157 logical_end = get_unaligned(&largest->start_sect)
158 + get_unaligned(&largest->nr_sects);
160 /* This is for >1023 cylinders */
161 ext_cyl = (logical_end - (end_head * end_sector + end_sector))
162 / (end_head + 1) / end_sector;
163 ext_physical_end = ext_cyl * (end_head + 1) * end_sector +
164 end_head * end_sector + end_sector;
167 printk("scsicam_bios_param : logical_end=%d physical_end=%d ext_physical_end=%d ext_cyl=%d\n"
168 ,logical_end, physical_end, ext_physical_end, ext_cyl);
171 if ((logical_end == physical_end) ||
172 (end_cyl == 1023 && ext_physical_end == logical_end)) {
175 *cyls = capacity / ((end_head + 1) * end_sector);
179 printk("scsicam_bios_param : logical (%u) != physical (%u)\n",
180 logical_end, physical_end);
185 EXPORT_SYMBOL(scsi_partsize);
188 * Function : static int setsize(unsigned long capacity,unsigned int *cyls,
189 * unsigned int *hds, unsigned int *secs);
191 * Purpose : to determine a near-optimal int 0x13 mapping for a
192 * SCSI disk in terms of lost space of size capacity, storing
193 * the results in *cyls, *hds, and *secs.
195 * Returns : -1 on failure, 0 on success.
205 * Information technology -
206 * SCSI-2 Common access method
207 * transport and SCSI interface module
211 * setsize() converts a read capacity value to int 13h
212 * head-cylinder-sector requirements. It minimizes the value for
213 * number of heads and maximizes the number of cylinders. This
214 * will support rather large disks before the number of heads
215 * will not fit in 4 bits (or 6 bits). This algorithm also
216 * minimizes the number of sectors that will be unused at the end
217 * of the disk while allowing for very large disks to be
218 * accommodated. This algorithm does not use physical geometry.
221 static int setsize(unsigned long capacity, unsigned int *cyls, unsigned int *hds,
225 unsigned long heads, sectors, cylinders, temp;
227 cylinders = 1024L; /* Set number of cylinders to max */
228 sectors = 62L; /* Maximize sectors per track */
230 temp = cylinders * sectors; /* Compute divisor for heads */
231 heads = capacity / temp; /* Compute value for number of heads */
232 if (capacity % temp) { /* If no remainder, done! */
233 heads++; /* Else, increment number of heads */
234 temp = cylinders * heads; /* Compute divisor for sectors */
235 sectors = capacity / temp; /* Compute value for sectors per
237 if (capacity % temp) { /* If no remainder, done! */
238 sectors++; /* Else, increment number of sectors */
239 temp = heads * sectors; /* Compute divisor for cylinders */
240 cylinders = capacity / temp; /* Compute number of cylinders */
244 rv = (unsigned) -1; /* Give error if 0 cylinders */
246 *cyls = (unsigned int) cylinders; /* Stuff return values */
247 *secs = (unsigned int) sectors;
248 *hds = (unsigned int) heads;