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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"

#include <scsi/scsicam.h>

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 = scsi_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 scsi_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.

 *

 */

int scsi_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);

}