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678e275732
As sparse correctly pointed out, scsi_partsize should use get_unaligned_le32 to read PC partition tables from disk, as they are little endian. The result of this bug is that we returned incorrect geometries on big endian systems when using the scsicam variant. Which probably doesn't matter as only old x86 systems every cared about the geometry. Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com> Reviewed-by: Hannes Reinecke <hare@suse.de>
260 lines
7.7 KiB
C
260 lines
7.7 KiB
C
/*
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* scsicam.c - SCSI CAM support functions, use for HDIO_GETGEO, etc.
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*
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* Copyright 1993, 1994 Drew Eckhardt
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* Visionary Computing
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* (Unix and Linux consulting and custom programming)
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* drew@Colorado.EDU
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* +1 (303) 786-7975
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*
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* For more information, please consult the SCSI-CAM draft.
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*/
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#include <linux/module.h>
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#include <linux/slab.h>
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#include <linux/fs.h>
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#include <linux/genhd.h>
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#include <linux/kernel.h>
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#include <linux/blkdev.h>
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#include <asm/unaligned.h>
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#include <scsi/scsicam.h>
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static int setsize(unsigned long capacity, unsigned int *cyls, unsigned int *hds,
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unsigned int *secs);
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/**
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* scsi_bios_ptable - Read PC partition table out of first sector of device.
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* @dev: from this device
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*
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* Description: Reads the first sector from the device and returns %0x42 bytes
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* starting at offset %0x1be.
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* Returns: partition table in kmalloc(GFP_KERNEL) memory, or NULL on error.
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*/
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unsigned char *scsi_bios_ptable(struct block_device *dev)
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{
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unsigned char *res = kmalloc(66, GFP_KERNEL);
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if (res) {
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struct block_device *bdev = dev->bd_contains;
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Sector sect;
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void *data = read_dev_sector(bdev, 0, §);
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if (data) {
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memcpy(res, data + 0x1be, 66);
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put_dev_sector(sect);
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} else {
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kfree(res);
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res = NULL;
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}
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}
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return res;
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}
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EXPORT_SYMBOL(scsi_bios_ptable);
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/**
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* scsicam_bios_param - Determine geometry of a disk in cylinders/heads/sectors.
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* @bdev: which device
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* @capacity: size of the disk in sectors
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* @ip: return value: ip[0]=heads, ip[1]=sectors, ip[2]=cylinders
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*
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* Description : determine the BIOS mapping/geometry used for a drive in a
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* SCSI-CAM system, storing the results in ip as required
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* by the HDIO_GETGEO ioctl().
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*
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* Returns : -1 on failure, 0 on success.
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*/
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int scsicam_bios_param(struct block_device *bdev, sector_t capacity, int *ip)
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{
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unsigned char *p;
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u64 capacity64 = capacity; /* Suppress gcc warning */
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int ret;
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p = scsi_bios_ptable(bdev);
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if (!p)
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return -1;
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/* try to infer mapping from partition table */
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ret = scsi_partsize(p, (unsigned long)capacity, (unsigned int *)ip + 2,
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(unsigned int *)ip + 0, (unsigned int *)ip + 1);
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kfree(p);
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if (ret == -1 && capacity64 < (1ULL << 32)) {
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/* pick some standard mapping with at most 1024 cylinders,
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and at most 62 sectors per track - this works up to
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7905 MB */
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ret = setsize((unsigned long)capacity, (unsigned int *)ip + 2,
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(unsigned int *)ip + 0, (unsigned int *)ip + 1);
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}
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/* if something went wrong, then apparently we have to return
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a geometry with more than 1024 cylinders */
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if (ret || ip[0] > 255 || ip[1] > 63) {
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if ((capacity >> 11) > 65534) {
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ip[0] = 255;
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ip[1] = 63;
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} else {
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ip[0] = 64;
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ip[1] = 32;
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}
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if (capacity > 65535*63*255)
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ip[2] = 65535;
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else
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ip[2] = (unsigned long)capacity / (ip[0] * ip[1]);
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}
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return 0;
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}
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EXPORT_SYMBOL(scsicam_bios_param);
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/**
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* scsi_partsize - Parse cylinders/heads/sectors from PC partition table
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* @buf: partition table, see scsi_bios_ptable()
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* @capacity: size of the disk in sectors
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* @cyls: put cylinders here
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* @hds: put heads here
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* @secs: put sectors here
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*
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* Description: determine the BIOS mapping/geometry used to create the partition
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* table, storing the results in *cyls, *hds, and *secs
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*
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* Returns: -1 on failure, 0 on success.
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*/
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int scsi_partsize(unsigned char *buf, unsigned long capacity,
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unsigned int *cyls, unsigned int *hds, unsigned int *secs)
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{
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struct partition *p = (struct partition *)buf, *largest = NULL;
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int i, largest_cyl;
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int cyl, ext_cyl, end_head, end_cyl, end_sector;
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unsigned int logical_end, physical_end, ext_physical_end;
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if (*(unsigned short *) (buf + 64) == 0xAA55) {
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for (largest_cyl = -1, i = 0; i < 4; ++i, ++p) {
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if (!p->sys_ind)
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continue;
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#ifdef DEBUG
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printk("scsicam_bios_param : partition %d has system \n",
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i);
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#endif
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cyl = p->cyl + ((p->sector & 0xc0) << 2);
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if (cyl > largest_cyl) {
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largest_cyl = cyl;
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largest = p;
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}
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}
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}
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if (largest) {
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end_cyl = largest->end_cyl + ((largest->end_sector & 0xc0) << 2);
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end_head = largest->end_head;
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end_sector = largest->end_sector & 0x3f;
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if (end_head + 1 == 0 || end_sector == 0)
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return -1;
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#ifdef DEBUG
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printk("scsicam_bios_param : end at h = %d, c = %d, s = %d\n",
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end_head, end_cyl, end_sector);
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#endif
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physical_end = end_cyl * (end_head + 1) * end_sector +
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end_head * end_sector + end_sector;
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/* This is the actual _sector_ number at the end */
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logical_end = get_unaligned_le32(&largest->start_sect)
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+ get_unaligned_le32(&largest->nr_sects);
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/* This is for >1023 cylinders */
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ext_cyl = (logical_end - (end_head * end_sector + end_sector))
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/ (end_head + 1) / end_sector;
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ext_physical_end = ext_cyl * (end_head + 1) * end_sector +
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end_head * end_sector + end_sector;
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#ifdef DEBUG
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printk("scsicam_bios_param : logical_end=%d physical_end=%d ext_physical_end=%d ext_cyl=%d\n"
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,logical_end, physical_end, ext_physical_end, ext_cyl);
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#endif
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if ((logical_end == physical_end) ||
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(end_cyl == 1023 && ext_physical_end == logical_end)) {
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*secs = end_sector;
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*hds = end_head + 1;
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*cyls = capacity / ((end_head + 1) * end_sector);
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return 0;
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}
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#ifdef DEBUG
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printk("scsicam_bios_param : logical (%u) != physical (%u)\n",
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logical_end, physical_end);
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#endif
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}
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return -1;
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}
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EXPORT_SYMBOL(scsi_partsize);
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/*
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* Function : static int setsize(unsigned long capacity,unsigned int *cyls,
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* unsigned int *hds, unsigned int *secs);
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*
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* Purpose : to determine a near-optimal int 0x13 mapping for a
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* SCSI disk in terms of lost space of size capacity, storing
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* the results in *cyls, *hds, and *secs.
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*
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* Returns : -1 on failure, 0 on success.
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*
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* Extracted from
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*
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* WORKING X3T9.2
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* DRAFT 792D
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* see http://www.t10.org/ftp/t10/drafts/cam/cam-r12b.pdf
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*
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* Revision 6
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* 10-MAR-94
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* Information technology -
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* SCSI-2 Common access method
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* transport and SCSI interface module
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*
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* ANNEX A :
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*
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* setsize() converts a read capacity value to int 13h
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* head-cylinder-sector requirements. It minimizes the value for
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* number of heads and maximizes the number of cylinders. This
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* will support rather large disks before the number of heads
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* will not fit in 4 bits (or 6 bits). This algorithm also
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* minimizes the number of sectors that will be unused at the end
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* of the disk while allowing for very large disks to be
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* accommodated. This algorithm does not use physical geometry.
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*/
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static int setsize(unsigned long capacity, unsigned int *cyls, unsigned int *hds,
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unsigned int *secs)
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{
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unsigned int rv = 0;
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unsigned long heads, sectors, cylinders, temp;
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cylinders = 1024L; /* Set number of cylinders to max */
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sectors = 62L; /* Maximize sectors per track */
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temp = cylinders * sectors; /* Compute divisor for heads */
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heads = capacity / temp; /* Compute value for number of heads */
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if (capacity % temp) { /* If no remainder, done! */
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heads++; /* Else, increment number of heads */
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temp = cylinders * heads; /* Compute divisor for sectors */
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sectors = capacity / temp; /* Compute value for sectors per
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track */
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if (capacity % temp) { /* If no remainder, done! */
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sectors++; /* Else, increment number of sectors */
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temp = heads * sectors; /* Compute divisor for cylinders */
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cylinders = capacity / temp; /* Compute number of cylinders */
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}
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}
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if (cylinders == 0)
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rv = (unsigned) -1; /* Give error if 0 cylinders */
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*cyls = (unsigned int) cylinders; /* Stuff return values */
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*secs = (unsigned int) sectors;
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*hds = (unsigned int) heads;
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return (rv);
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}
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