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
,
28 * scsi_bios_ptable - Read PC partition table out of first sector of device.
29 * @dev: from this device
31 * Description: Reads the first sector from the device and returns %0x42 bytes
32 * starting at offset %0x1be.
33 * Returns: partition table in kmalloc(GFP_KERNEL) memory, or NULL on error.
35 unsigned char *scsi_bios_ptable(struct block_device
*dev
)
37 unsigned char *res
= kmalloc(66, GFP_KERNEL
);
39 struct block_device
*bdev
= dev
->bd_contains
;
41 void *data
= read_dev_sector(bdev
, 0, §
);
43 memcpy(res
, data
+ 0x1be, 66);
52 EXPORT_SYMBOL(scsi_bios_ptable
);
55 * scsicam_bios_param - Determine geometry of a disk in cylinders/heads/sectors.
57 * @capacity: size of the disk in sectors
58 * @ip: return value: ip[0]=heads, ip[1]=sectors, ip[2]=cylinders
60 * Description : determine the BIOS mapping/geometry used for a drive in a
61 * SCSI-CAM system, storing the results in ip as required
62 * by the HDIO_GETGEO ioctl().
64 * Returns : -1 on failure, 0 on success.
67 int scsicam_bios_param(struct block_device
*bdev
, sector_t capacity
, int *ip
)
70 u64 capacity64
= capacity
; /* Suppress gcc warning */
73 p
= scsi_bios_ptable(bdev
);
77 /* try to infer mapping from partition table */
78 ret
= scsi_partsize(p
, (unsigned long)capacity
, (unsigned int *)ip
+ 2,
79 (unsigned int *)ip
+ 0, (unsigned int *)ip
+ 1);
82 if (ret
== -1 && capacity64
< (1ULL << 32)) {
83 /* pick some standard mapping with at most 1024 cylinders,
84 and at most 62 sectors per track - this works up to
86 ret
= setsize((unsigned long)capacity
, (unsigned int *)ip
+ 2,
87 (unsigned int *)ip
+ 0, (unsigned int *)ip
+ 1);
90 /* if something went wrong, then apparently we have to return
91 a geometry with more than 1024 cylinders */
92 if (ret
|| ip
[0] > 255 || ip
[1] > 63) {
93 if ((capacity
>> 11) > 65534) {
101 if (capacity
> 65535*63*255)
104 ip
[2] = (unsigned long)capacity
/ (ip
[0] * ip
[1]);
109 EXPORT_SYMBOL(scsicam_bios_param
);
112 * scsi_partsize - Parse cylinders/heads/sectors from PC partition table
113 * @buf: partition table, see scsi_bios_ptable()
114 * @capacity: size of the disk in sectors
115 * @cyls: put cylinders here
116 * @hds: put heads here
117 * @secs: put sectors here
119 * Description: determine the BIOS mapping/geometry used to create the partition
120 * table, storing the results in *cyls, *hds, and *secs
122 * Returns: -1 on failure, 0 on success.
125 int scsi_partsize(unsigned char *buf
, unsigned long capacity
,
126 unsigned int *cyls
, unsigned int *hds
, unsigned int *secs
)
128 struct partition
*p
= (struct partition
*)buf
, *largest
= NULL
;
130 int cyl
, ext_cyl
, end_head
, end_cyl
, end_sector
;
131 unsigned int logical_end
, physical_end
, ext_physical_end
;
134 if (*(unsigned short *) (buf
+ 64) == 0xAA55) {
135 for (largest_cyl
= -1, i
= 0; i
< 4; ++i
, ++p
) {
139 printk("scsicam_bios_param : partition %d has system \n",
142 cyl
= p
->cyl
+ ((p
->sector
& 0xc0) << 2);
143 if (cyl
> largest_cyl
) {
150 end_cyl
= largest
->end_cyl
+ ((largest
->end_sector
& 0xc0) << 2);
151 end_head
= largest
->end_head
;
152 end_sector
= largest
->end_sector
& 0x3f;
154 if (end_head
+ 1 == 0 || end_sector
== 0)
158 printk("scsicam_bios_param : end at h = %d, c = %d, s = %d\n",
159 end_head
, end_cyl
, end_sector
);
162 physical_end
= end_cyl
* (end_head
+ 1) * end_sector
+
163 end_head
* end_sector
+ end_sector
;
165 /* This is the actual _sector_ number at the end */
166 logical_end
= get_unaligned(&largest
->start_sect
)
167 + get_unaligned(&largest
->nr_sects
);
169 /* This is for >1023 cylinders */
170 ext_cyl
= (logical_end
- (end_head
* end_sector
+ end_sector
))
171 / (end_head
+ 1) / end_sector
;
172 ext_physical_end
= ext_cyl
* (end_head
+ 1) * end_sector
+
173 end_head
* end_sector
+ end_sector
;
176 printk("scsicam_bios_param : logical_end=%d physical_end=%d ext_physical_end=%d ext_cyl=%d\n"
177 ,logical_end
, physical_end
, ext_physical_end
, ext_cyl
);
180 if ((logical_end
== physical_end
) ||
181 (end_cyl
== 1023 && ext_physical_end
== logical_end
)) {
184 *cyls
= capacity
/ ((end_head
+ 1) * end_sector
);
188 printk("scsicam_bios_param : logical (%u) != physical (%u)\n",
189 logical_end
, physical_end
);
194 EXPORT_SYMBOL(scsi_partsize
);
197 * Function : static int setsize(unsigned long capacity,unsigned int *cyls,
198 * unsigned int *hds, unsigned int *secs);
200 * Purpose : to determine a near-optimal int 0x13 mapping for a
201 * SCSI disk in terms of lost space of size capacity, storing
202 * the results in *cyls, *hds, and *secs.
204 * Returns : -1 on failure, 0 on success.
210 * see http://www.t10.org/ftp/t10/drafts/cam/cam-r12b.pdf
214 * Information technology -
215 * SCSI-2 Common access method
216 * transport and SCSI interface module
220 * setsize() converts a read capacity value to int 13h
221 * head-cylinder-sector requirements. It minimizes the value for
222 * number of heads and maximizes the number of cylinders. This
223 * will support rather large disks before the number of heads
224 * will not fit in 4 bits (or 6 bits). This algorithm also
225 * minimizes the number of sectors that will be unused at the end
226 * of the disk while allowing for very large disks to be
227 * accommodated. This algorithm does not use physical geometry.
230 static int setsize(unsigned long capacity
, unsigned int *cyls
, unsigned int *hds
,
234 unsigned long heads
, sectors
, cylinders
, temp
;
236 cylinders
= 1024L; /* Set number of cylinders to max */
237 sectors
= 62L; /* Maximize sectors per track */
239 temp
= cylinders
* sectors
; /* Compute divisor for heads */
240 heads
= capacity
/ temp
; /* Compute value for number of heads */
241 if (capacity
% temp
) { /* If no remainder, done! */
242 heads
++; /* Else, increment number of heads */
243 temp
= cylinders
* heads
; /* Compute divisor for sectors */
244 sectors
= capacity
/ temp
; /* Compute value for sectors per
246 if (capacity
% temp
) { /* If no remainder, done! */
247 sectors
++; /* Else, increment number of sectors */
248 temp
= heads
* sectors
; /* Compute divisor for cylinders */
249 cylinders
= capacity
/ temp
; /* Compute number of cylinders */
253 rv
= (unsigned) -1; /* Give error if 0 cylinders */
255 *cyls
= (unsigned int) cylinders
; /* Stuff return values */
256 *secs
= (unsigned int) sectors
;
257 *hds
= (unsigned int) heads
;
This page took 0.035117 seconds and 5 git commands to generate.