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;
32 struct buffer_head *bh = __bread(bdev, 0, block_size(bdev));
34 memcpy(res, bh->b_data + 0x1be, 66);
45 * Function : int scsicam_bios_param (struct block_device *bdev, ector_t capacity, int *ip)
47 * Purpose : to determine the BIOS mapping used for a drive in a
48 * SCSI-CAM system, storing the results in ip as required
49 * by the HDIO_GETGEO ioctl().
51 * Returns : -1 on failure, 0 on success.
55 int scsicam_bios_param(struct block_device *bdev, sector_t capacity, int *ip)
60 p = scsi_bios_ptable(bdev);
64 /* try to infer mapping from partition table */
65 ret = scsi_partsize(p, (unsigned long)capacity, (unsigned int *)ip + 2,
66 (unsigned int *)ip + 0, (unsigned int *)ip + 1);
70 /* pick some standard mapping with at most 1024 cylinders,
71 and at most 62 sectors per track - this works up to
73 ret = setsize((unsigned long)capacity, (unsigned int *)ip + 2,
74 (unsigned int *)ip + 0, (unsigned int *)ip + 1);
77 /* if something went wrong, then apparently we have to return
78 a geometry with more than 1024 cylinders */
79 if (ret || ip[0] > 255 || ip[1] > 63) {
80 if ((capacity >> 11) > 65534) {
88 if (capacity > 65535*63*255)
91 ip[2] = (unsigned long)capacity / (ip[0] * ip[1]);
98 * Function : static int scsi_partsize(unsigned char *buf, unsigned long
99 * capacity,unsigned int *cyls, unsigned int *hds, unsigned int *secs);
101 * Purpose : to determine the BIOS mapping used to create the partition
102 * table, storing the results in *cyls, *hds, and *secs
104 * Returns : -1 on failure, 0 on success.
108 int scsi_partsize(unsigned char *buf, unsigned long capacity,
109 unsigned int *cyls, unsigned int *hds, unsigned int *secs)
111 struct partition *p = (struct partition *)buf, *largest = NULL;
113 int cyl, ext_cyl, end_head, end_cyl, end_sector;
114 unsigned int logical_end, physical_end, ext_physical_end;
117 if (*(unsigned short *) (buf + 64) == 0xAA55) {
118 for (largest_cyl = -1, i = 0; i < 4; ++i, ++p) {
122 printk("scsicam_bios_param : partition %d has system \n",
125 cyl = p->cyl + ((p->sector & 0xc0) << 2);
126 if (cyl > largest_cyl) {
133 end_cyl = largest->end_cyl + ((largest->end_sector & 0xc0) << 2);
134 end_head = largest->end_head;
135 end_sector = largest->end_sector & 0x3f;
137 if (end_head + 1 == 0 || end_sector == 0)
141 printk("scsicam_bios_param : end at h = %d, c = %d, s = %d\n",
142 end_head, end_cyl, end_sector);
145 physical_end = end_cyl * (end_head + 1) * end_sector +
146 end_head * end_sector + end_sector;
148 /* This is the actual _sector_ number at the end */
149 logical_end = get_unaligned(&largest->start_sect)
150 + get_unaligned(&largest->nr_sects);
152 /* This is for >1023 cylinders */
153 ext_cyl = (logical_end - (end_head * end_sector + end_sector))
154 / (end_head + 1) / end_sector;
155 ext_physical_end = ext_cyl * (end_head + 1) * end_sector +
156 end_head * end_sector + end_sector;
159 printk("scsicam_bios_param : logical_end=%d physical_end=%d ext_physical_end=%d ext_cyl=%d\n"
160 ,logical_end, physical_end, ext_physical_end, ext_cyl);
163 if ((logical_end == physical_end) ||
164 (end_cyl == 1023 && ext_physical_end == logical_end)) {
167 *cyls = capacity / ((end_head + 1) * end_sector);
171 printk("scsicam_bios_param : logical (%u) != physical (%u)\n",
172 logical_end, physical_end);
179 * Function : static int setsize(unsigned long capacity,unsigned int *cyls,
180 * unsigned int *hds, unsigned int *secs);
182 * Purpose : to determine a near-optimal int 0x13 mapping for a
183 * SCSI disk in terms of lost space of size capacity, storing
184 * the results in *cyls, *hds, and *secs.
186 * Returns : -1 on failure, 0 on success.
196 * Information technology -
197 * SCSI-2 Common access method
198 * transport and SCSI interface module
202 * setsize() converts a read capacity value to int 13h
203 * head-cylinder-sector requirements. It minimizes the value for
204 * number of heads and maximizes the number of cylinders. This
205 * will support rather large disks before the number of heads
206 * will not fit in 4 bits (or 6 bits). This algorithm also
207 * minimizes the number of sectors that will be unused at the end
208 * of the disk while allowing for very large disks to be
209 * accommodated. This algorithm does not use physical geometry.
212 static int setsize(unsigned long capacity, unsigned int *cyls, unsigned int *hds,
216 unsigned long heads, sectors, cylinders, temp;
218 cylinders = 1024L; /* Set number of cylinders to max */
219 sectors = 62L; /* Maximize sectors per track */
221 temp = cylinders * sectors; /* Compute divisor for heads */
222 heads = capacity / temp; /* Compute value for number of heads */
223 if (capacity % temp) { /* If no remainder, done! */
224 heads++; /* Else, increment number of heads */
225 temp = cylinders * heads; /* Compute divisor for sectors */
226 sectors = capacity / temp; /* Compute value for sectors per
228 if (capacity % temp) { /* If no remainder, done! */
229 sectors++; /* Else, increment number of sectors */
230 temp = heads * sectors; /* Compute divisor for cylinders */
231 cylinders = capacity / temp; /* Compute number of cylinders */
235 rv = (unsigned) -1; /* Give error if 0 cylinders */
237 *cyls = (unsigned int) cylinders; /* Stuff return values */
238 *secs = (unsigned int) sectors;
239 *hds = (unsigned int) heads;