259 lines
7.6 KiB
C
259 lines
7.6 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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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 <linux/msdos_partition.h>
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#include <asm/unaligned.h>
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#include <scsi/scsicam.h>
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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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struct address_space *mapping = dev->bd_contains->bd_inode->i_mapping;
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unsigned char *res = NULL;
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struct page *page;
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page = read_mapping_page(mapping, 0, NULL);
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if (IS_ERR(page))
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return NULL;
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if (!PageError(page))
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res = kmemdup(page_address(page) + 0x1be, 66, GFP_KERNEL);
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put_page(page);
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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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* scsi_partsize - Parse cylinders/heads/sectors from PC partition table
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* @bdev: block device to parse
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* @capacity: size of the disk in sectors
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* @geom: output in form of [hds, cylinders, sectors]
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*
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* Determine the BIOS mapping/geometry used to create the partition
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* table, storing the results in @geom.
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*
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* Returns: %false on failure, %true on success.
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*/
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bool scsi_partsize(struct block_device *bdev, sector_t capacity, int geom[3])
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{
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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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struct msdos_partition *p, *largest = NULL;
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void *buf;
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int ret = false;
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buf = scsi_bios_ptable(bdev);
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if (!buf)
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return false;
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if (*(unsigned short *) (buf + 64) == 0xAA55) {
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int largest_cyl = -1, i;
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for (i = 0, p = buf; 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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goto out_free_buf;
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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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geom[0] = end_head + 1;
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geom[1] = end_sector;
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geom[2] = (unsigned long)capacity /
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((end_head + 1) * end_sector);
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ret = true;
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goto out_free_buf;
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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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out_free_buf:
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kfree(buf);
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return ret;
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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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/**
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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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u64 capacity64 = capacity; /* Suppress gcc warning */
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int ret = 0;
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/* try to infer mapping from partition table */
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if (scsi_partsize(bdev, capacity, ip))
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return 0;
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if (capacity64 < (1ULL << 32)) {
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/*
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* Pick some standard mapping with at most 1024 cylinders, and
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* at most 62 sectors per track - this works up to 7905 MB.
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*/
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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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/*
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* If something went wrong, then apparently we have to return a geometry
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* with more than 1024 cylinders.
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*/
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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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