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>
16 #include <linux/genhd.h>
17 #include <linux/kernel.h>
18 #include <linux/blkdev.h>
19 #include <linux/buffer_head.h>
20 #include <asm/unaligned.h>
23 #include <scsi/scsicam.h>
25 static int setsize(unsigned long capacity, unsigned int *cyls, unsigned int *hds,
28 unsigned char *scsi_bios_ptable(struct block_device *dev)
30 unsigned char *res = kmalloc(66, GFP_KERNEL);
32 struct block_device *bdev = dev->bd_contains;
33 struct buffer_head *bh = __bread(bdev, 0, block_size(bdev));
35 memcpy(res, bh->b_data + 0x1be, 66);
46 * Function : int scsicam_bios_param (struct block_device *bdev, ector_t capacity, int *ip)
48 * Purpose : to determine the BIOS mapping used for a drive in a
49 * SCSI-CAM system, storing the results in ip as required
50 * by the HDIO_GETGEO ioctl().
52 * Returns : -1 on failure, 0 on success.
56 int scsicam_bios_param(struct block_device *bdev, sector_t capacity, int *ip)
61 p = scsi_bios_ptable(bdev);
65 /* try to infer mapping from partition table */
66 ret = scsi_partsize(p, (unsigned long)capacity, (unsigned int *)ip + 2,
67 (unsigned int *)ip + 0, (unsigned int *)ip + 1);
71 /* pick some standard mapping with at most 1024 cylinders,
72 and at most 62 sectors per track - this works up to
74 ret = setsize((unsigned long)capacity, (unsigned int *)ip + 2,
75 (unsigned int *)ip + 0, (unsigned int *)ip + 1);
78 /* if something went wrong, then apparently we have to return
79 a geometry with more than 1024 cylinders */
80 if (ret || ip[0] > 255 || ip[1] > 63) {
81 if ((capacity >> 11) > 65534) {
89 if (capacity > 65535*63*255)
92 ip[2] = (unsigned long)capacity / (ip[0] * ip[1]);
99 * Function : static int scsi_partsize(unsigned char *buf, unsigned long
100 * capacity,unsigned int *cyls, unsigned int *hds, unsigned int *secs);
102 * Purpose : to determine the BIOS mapping used to create the partition
103 * table, storing the results in *cyls, *hds, and *secs
105 * Returns : -1 on failure, 0 on success.
109 int scsi_partsize(unsigned char *buf, unsigned long capacity,
110 unsigned int *cyls, unsigned int *hds, unsigned int *secs)
112 struct partition *p = (struct partition *)buf, *largest = NULL;
114 int cyl, ext_cyl, end_head, end_cyl, end_sector;
115 unsigned int logical_end, physical_end, ext_physical_end;
118 if (*(unsigned short *) (buf + 64) == 0xAA55) {
119 for (largest_cyl = -1, i = 0; i < 4; ++i, ++p) {
123 printk("scsicam_bios_param : partition %d has system \n",
126 cyl = p->cyl + ((p->sector & 0xc0) << 2);
127 if (cyl > largest_cyl) {
134 end_cyl = largest->end_cyl + ((largest->end_sector & 0xc0) << 2);
135 end_head = largest->end_head;
136 end_sector = largest->end_sector & 0x3f;
138 if (end_head + 1 == 0 || end_sector == 0)
142 printk("scsicam_bios_param : end at h = %d, c = %d, s = %d\n",
143 end_head, end_cyl, end_sector);
146 physical_end = end_cyl * (end_head + 1) * end_sector +
147 end_head * end_sector + end_sector;
149 /* This is the actual _sector_ number at the end */
150 logical_end = get_unaligned(&largest->start_sect)
151 + get_unaligned(&largest->nr_sects);
153 /* This is for >1023 cylinders */
154 ext_cyl = (logical_end - (end_head * end_sector + end_sector))
155 / (end_head + 1) / end_sector;
156 ext_physical_end = ext_cyl * (end_head + 1) * end_sector +
157 end_head * end_sector + end_sector;
160 printk("scsicam_bios_param : logical_end=%d physical_end=%d ext_physical_end=%d ext_cyl=%d\n"
161 ,logical_end, physical_end, ext_physical_end, ext_cyl);
164 if ((logical_end == physical_end) ||
165 (end_cyl == 1023 && ext_physical_end == logical_end)) {
168 *cyls = capacity / ((end_head + 1) * end_sector);
172 printk("scsicam_bios_param : logical (%u) != physical (%u)\n",
173 logical_end, physical_end);
180 * Function : static int setsize(unsigned long capacity,unsigned int *cyls,
181 * unsigned int *hds, unsigned int *secs);
183 * Purpose : to determine a near-optimal int 0x13 mapping for a
184 * SCSI disk in terms of lost space of size capacity, storing
185 * the results in *cyls, *hds, and *secs.
187 * Returns : -1 on failure, 0 on success.
197 * Information technology -
198 * SCSI-2 Common access method
199 * transport and SCSI interface module
203 * setsize() converts a read capacity value to int 13h
204 * head-cylinder-sector requirements. It minimizes the value for
205 * number of heads and maximizes the number of cylinders. This
206 * will support rather large disks before the number of heads
207 * will not fit in 4 bits (or 6 bits). This algorithm also
208 * minimizes the number of sectors that will be unused at the end
209 * of the disk while allowing for very large disks to be
210 * accommodated. This algorithm does not use physical geometry.
213 static int setsize(unsigned long capacity, unsigned int *cyls, unsigned int *hds,
217 unsigned long heads, sectors, cylinders, temp;
219 cylinders = 1024L; /* Set number of cylinders to max */
220 sectors = 62L; /* Maximize sectors per track */
222 temp = cylinders * sectors; /* Compute divisor for heads */
223 heads = capacity / temp; /* Compute value for number of heads */
224 if (capacity % temp) { /* If no remainder, done! */
225 heads++; /* Else, increment number of heads */
226 temp = cylinders * heads; /* Compute divisor for sectors */
227 sectors = capacity / temp; /* Compute value for sectors per
229 if (capacity % temp) { /* If no remainder, done! */
230 sectors++; /* Else, increment number of sectors */
231 temp = heads * sectors; /* Compute divisor for cylinders */
232 cylinders = capacity / temp; /* Compute number of cylinders */
236 rv = (unsigned) -1; /* Give error if 0 cylinders */
238 *cyls = (unsigned int) cylinders; /* Stuff return values */
239 *secs = (unsigned int) sectors;
240 *hds = (unsigned int) heads;