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 #define __NO_VERSION__
14 #include <linux/module.h>
17 #include <linux/genhd.h>
18 #include <linux/kernel.h>
19 #include <linux/blk.h>
20 #include <asm/unaligned.h>
24 #include <scsi/scsicam.h>
26 static int setsize(unsigned long capacity, unsigned int *cyls, unsigned int *hds,
31 * Function : int scsicam_bios_param (Disk *disk, int dev, int *ip)
33 * Purpose : to determine the BIOS mapping used for a drive in a
34 * SCSI-CAM system, storing the results in ip as required
35 * by the HDIO_GETGEO ioctl().
37 * Returns : -1 on failure, 0 on success.
41 int scsicam_bios_param(Disk * disk, /* SCSI disk */
42 kdev_t dev, /* Device major, minor */
43 int *ip /* Heads, sectors, cylinders in that order */ )
45 struct buffer_head *bh;
47 int size = disk->capacity;
48 unsigned long temp_cyl;
50 if (!(bh = bread(MKDEV(MAJOR(dev), MINOR(dev)&~0xf), 0, block_size(dev))))
53 /* try to infer mapping from partition table */
54 ret_code = scsi_partsize(bh, (unsigned long) size, (unsigned int *) ip + 2,
55 (unsigned int *) ip + 0, (unsigned int *) ip + 1);
59 /* pick some standard mapping with at most 1024 cylinders,
60 and at most 62 sectors per track - this works up to
62 ret_code = setsize((unsigned long) size, (unsigned int *) ip + 2,
63 (unsigned int *) ip + 0, (unsigned int *) ip + 1);
65 /* if something went wrong, then apparently we have to return
66 a geometry with more than 1024 cylinders */
67 if (ret_code || ip[0] > 255 || ip[1] > 63) {
70 temp_cyl = size / (ip[0] * ip[1]);
71 if (temp_cyl > 65534) {
75 ip[2] = size / (ip[0] * ip[1]);
81 * Function : static int scsi_partsize(struct buffer_head *bh, unsigned long
82 * capacity,unsigned int *cyls, unsigned int *hds, unsigned int *secs);
84 * Purpose : to determine the BIOS mapping used to create the partition
85 * table, storing the results in *cyls, *hds, and *secs
87 * Returns : -1 on failure, 0 on success.
91 int scsi_partsize(struct buffer_head *bh, unsigned long capacity,
92 unsigned int *cyls, unsigned int *hds, unsigned int *secs)
94 struct partition *p, *largest = NULL;
96 int cyl, ext_cyl, end_head, end_cyl, end_sector;
97 unsigned int logical_end, physical_end, ext_physical_end;
100 if (*(unsigned short *) (bh->b_data + 510) == 0xAA55) {
101 for (largest_cyl = -1, p = (struct partition *)
102 (0x1BE + bh->b_data), i = 0; i < 4; ++i, ++p) {
106 printk("scsicam_bios_param : partition %d has system \n",
109 cyl = p->cyl + ((p->sector & 0xc0) << 2);
110 if (cyl > largest_cyl) {
117 end_cyl = largest->end_cyl + ((largest->end_sector & 0xc0) << 2);
118 end_head = largest->end_head;
119 end_sector = largest->end_sector & 0x3f;
121 if (end_head + 1 == 0 || end_sector == 0)
125 printk("scsicam_bios_param : end at h = %d, c = %d, s = %d\n",
126 end_head, end_cyl, end_sector);
129 physical_end = end_cyl * (end_head + 1) * end_sector +
130 end_head * end_sector + end_sector;
132 /* This is the actual _sector_ number at the end */
133 logical_end = get_unaligned(&largest->start_sect)
134 + get_unaligned(&largest->nr_sects);
136 /* This is for >1023 cylinders */
137 ext_cyl = (logical_end - (end_head * end_sector + end_sector))
138 / (end_head + 1) / end_sector;
139 ext_physical_end = ext_cyl * (end_head + 1) * end_sector +
140 end_head * end_sector + end_sector;
143 printk("scsicam_bios_param : logical_end=%d physical_end=%d ext_physical_end=%d ext_cyl=%d\n"
144 ,logical_end, physical_end, ext_physical_end, ext_cyl);
147 if ((logical_end == physical_end) ||
148 (end_cyl == 1023 && ext_physical_end == logical_end)) {
151 *cyls = capacity / ((end_head + 1) * end_sector);
155 printk("scsicam_bios_param : logical (%u) != physical (%u)\n",
156 logical_end, physical_end);
163 * Function : static int setsize(unsigned long capacity,unsigned int *cyls,
164 * unsigned int *hds, unsigned int *secs);
166 * Purpose : to determine a near-optimal int 0x13 mapping for a
167 * SCSI disk in terms of lost space of size capacity, storing
168 * the results in *cyls, *hds, and *secs.
170 * Returns : -1 on failure, 0 on success.
180 * Information technology -
181 * SCSI-2 Common access method
182 * transport and SCSI interface module
186 * setsize() converts a read capacity value to int 13h
187 * head-cylinder-sector requirements. It minimizes the value for
188 * number of heads and maximizes the number of cylinders. This
189 * will support rather large disks before the number of heads
190 * will not fit in 4 bits (or 6 bits). This algorithm also
191 * minimizes the number of sectors that will be unused at the end
192 * of the disk while allowing for very large disks to be
193 * accommodated. This algorithm does not use physical geometry.
196 static int setsize(unsigned long capacity, unsigned int *cyls, unsigned int *hds,
200 unsigned long heads, sectors, cylinders, temp;
202 cylinders = 1024L; /* Set number of cylinders to max */
203 sectors = 62L; /* Maximize sectors per track */
205 temp = cylinders * sectors; /* Compute divisor for heads */
206 heads = capacity / temp; /* Compute value for number of heads */
207 if (capacity % temp) { /* If no remainder, done! */
208 heads++; /* Else, increment number of heads */
209 temp = cylinders * heads; /* Compute divisor for sectors */
210 sectors = capacity / temp; /* Compute value for sectors per
212 if (capacity % temp) { /* If no remainder, done! */
213 sectors++; /* Else, increment number of sectors */
214 temp = heads * sectors; /* Compute divisor for cylinders */
215 cylinders = capacity / temp; /* Compute number of cylinders */
219 rv = (unsigned) -1; /* Give error if 0 cylinders */
221 *cyls = (unsigned int) cylinders; /* Stuff return values */
222 *secs = (unsigned int) sectors;
223 *hds = (unsigned int) heads;