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/*
* scsicam.c - SCSI CAM support functions, use for HDIO_GETGEO, etc.
*
* Copyright 1993, 1994 Drew Eckhardt
* Visionary Computing
* (Unix and Linux consulting and custom programming)
* drew@Colorado.EDU
* +1 (303) 786-7975
*
* For more information, please consult the SCSI-CAM draft.
*/
/*
* Don't import our own symbols, as this would severely mess up our
* symbol tables.
*/
#define _SCSI_SYMS_VER_
#define __NO_VERSION__
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/genhd.h>
#include <linux/kernel.h>
#include <linux/blk.h>
#include <asm/unaligned.h>
#include "scsi.h"
#include "hosts.h"
#include "sd.h"
static int partsize(struct buffer_head *bh, unsigned long capacity,
unsigned int *cyls, unsigned int *hds, unsigned int *secs);
static int setsize(unsigned long capacity,unsigned int *cyls,unsigned int *hds,
unsigned int *secs);
/*
* Function : int scsicam_bios_param (Disk *disk, int dev, int *ip)
*
* Purpose : to determine the BIOS mapping used for a drive in a
* SCSI-CAM system, storing the results in ip as required
* by the HDIO_GETGEO ioctl().
*
* Returns : -1 on failure, 0 on success.
*
*/
int scsicam_bios_param (Disk *disk, /* SCSI disk */
kdev_t dev, /* Device major, minor */
int *ip /* Heads, sectors, cylinders in that order */) {
struct buffer_head *bh;
int ret_code;
int size = disk->capacity;
unsigned long temp_cyl;
if (!(bh = bread(MKDEV(MAJOR(dev), MINOR(dev)&~0xf), 0, 1024)))
return -1;
/* try to infer mapping from partition table */
ret_code = partsize (bh, (unsigned long) size, (unsigned int *) ip + 2,
(unsigned int *) ip + 0, (unsigned int *) ip + 1);
brelse (bh);
if (ret_code == -1) {
/* pick some standard mapping with at most 1024 cylinders,
and at most 62 sectors per track - this works up to
7905 MB */
ret_code = setsize ((unsigned long) size, (unsigned int *) ip + 2,
(unsigned int *) ip + 0, (unsigned int *) ip + 1);
}
/* if something went wrong, then apparently we have to return
a geometry with more than 1024 cylinders */
if (ret_code || ip[0] > 255 || ip[1] > 63) {
ip[0] = 64;
ip[1] = 32;
temp_cyl = size / (ip[0] * ip[1]);
if (temp_cyl > 65534) {
ip[0] = 255;
ip[1] = 63;
}
ip[2] = size / (ip[0] * ip[1]);
}
return 0;
}
/*
* Function : static int partsize(struct buffer_head *bh, unsigned long
* capacity,unsigned int *cyls, unsigned int *hds, unsigned int *secs);
*
* Purpose : to determine the BIOS mapping used to create the partition
* table, storing the results in *cyls, *hds, and *secs
*
* Returns : -1 on failure, 0 on success.
*
*/
static int partsize(struct buffer_head *bh, unsigned long capacity,
unsigned int *cyls, unsigned int *hds, unsigned int *secs) {
struct partition *p, *largest = NULL;
int i, largest_cyl;
int cyl, ext_cyl, end_head, end_cyl, end_sector;
unsigned int logical_end, physical_end, ext_physical_end;
if (*(unsigned short *) (bh->b_data+510) == 0xAA55) {
for (largest_cyl = -1, p = (struct partition *)
(0x1BE + bh->b_data), i = 0; i < 4; ++i, ++p) {
if (!p->sys_ind)
continue;
#ifdef DEBUG
printk ("scsicam_bios_param : partition %d has system \n",
i);
#endif
cyl = p->cyl + ((p->sector & 0xc0) << 2);
if (cyl > largest_cyl) {
largest_cyl = cyl;
largest = p;
}
}
}
if (largest) {
end_cyl = largest->end_cyl + ((largest->end_sector & 0xc0) << 2);
end_head = largest->end_head;
end_sector = largest->end_sector & 0x3f;
if( end_head + 1 == 0 || end_sector == 0 ) return -1;
#ifdef DEBUG
printk ("scsicam_bios_param : end at h = %d, c = %d, s = %d\n",
end_head, end_cyl, end_sector);
#endif
physical_end = end_cyl * (end_head + 1) * end_sector +
end_head * end_sector + end_sector;
/* This is the actual _sector_ number at the end */
logical_end = get_unaligned(&largest->start_sect)
+ get_unaligned(&largest->nr_sects);
/* This is for >1023 cylinders */
ext_cyl= (logical_end-(end_head * end_sector + end_sector))
/(end_head + 1) / end_sector;
ext_physical_end = ext_cyl * (end_head + 1) * end_sector +
end_head * end_sector + end_sector;
#ifdef DEBUG
printk("scsicam_bios_param : logical_end=%d physical_end=%d ext_physical_end=%d ext_cyl=%d\n"
,logical_end,physical_end,ext_physical_end,ext_cyl);
#endif
if ((logical_end == physical_end) ||
(end_cyl==1023 && ext_physical_end==logical_end)) {
*secs = end_sector;
*hds = end_head + 1;
*cyls = capacity / ((end_head + 1) * end_sector);
return 0;
}
#ifdef DEBUG
printk ("scsicam_bios_param : logical (%u) != physical (%u)\n",
logical_end, physical_end);
#endif
}
return -1;
}
/*
* Function : static int setsize(unsigned long capacity,unsigned int *cyls,
* unsigned int *hds, unsigned int *secs);
*
* Purpose : to determine a near-optimal int 0x13 mapping for a
* SCSI disk in terms of lost space of size capacity, storing
* the results in *cyls, *hds, and *secs.
*
* Returns : -1 on failure, 0 on success.
*
* Extracted from
*
* WORKING X3T9.2
* DRAFT 792D
*
*
* Revision 6
* 10-MAR-94
* Information technology -
* SCSI-2 Common access method
* transport and SCSI interface module
*
* ANNEX A :
*
* setsize() converts a read capacity value to int 13h
* head-cylinder-sector requirements. It minimizes the value for
* number of heads and maximizes the number of cylinders. This
* will support rather large disks before the number of heads
* will not fit in 4 bits (or 6 bits). This algorithm also
* minimizes the number of sectors that will be unused at the end
* of the disk while allowing for very large disks to be
* accommodated. This algorithm does not use physical geometry.
*/
static int setsize(unsigned long capacity,unsigned int *cyls,unsigned int *hds,
unsigned int *secs) {
unsigned int rv = 0;
unsigned long heads, sectors, cylinders, temp;
cylinders = 1024L; /* Set number of cylinders to max */
sectors = 62L; /* Maximize sectors per track */
temp = cylinders * sectors; /* Compute divisor for heads */
heads = capacity / temp; /* Compute value for number of heads */
if (capacity % temp) { /* If no remainder, done! */
heads++; /* Else, increment number of heads */
temp = cylinders * heads; /* Compute divisor for sectors */
sectors = capacity / temp; /* Compute value for sectors per
track */
if (capacity % temp) { /* If no remainder, done! */
sectors++; /* Else, increment number of sectors */
temp = heads * sectors; /* Compute divisor for cylinders */
cylinders = capacity / temp;/* Compute number of cylinders */
}
}
if (cylinders == 0) rv=(unsigned)-1;/* Give error if 0 cylinders */
*cyls = (unsigned int) cylinders; /* Stuff return values */
*secs = (unsigned int) sectors;
*hds = (unsigned int) heads;
return(rv);
}
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