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       1                 :            : // SPDX-License-Identifier: GPL-2.0
       2                 :            : /*
       3                 :            :  * scsicam.c - SCSI CAM support functions, use for HDIO_GETGEO, etc.
       4                 :            :  *
       5                 :            :  * Copyright 1993, 1994 Drew Eckhardt
       6                 :            :  *      Visionary Computing 
       7                 :            :  *      (Unix and Linux consulting and custom programming)
       8                 :            :  *      drew@Colorado.EDU
       9                 :            :  *      +1 (303) 786-7975
      10                 :            :  *
      11                 :            :  * For more information, please consult the SCSI-CAM draft.
      12                 :            :  */
      13                 :            : 
      14                 :            : #include <linux/module.h>
      15                 :            : #include <linux/slab.h>
      16                 :            : #include <linux/fs.h>
      17                 :            : #include <linux/genhd.h>
      18                 :            : #include <linux/kernel.h>
      19                 :            : #include <linux/blkdev.h>
      20                 :            : #include <asm/unaligned.h>
      21                 :            : 
      22                 :            : #include <scsi/scsicam.h>
      23                 :            : 
      24                 :            : 
      25                 :            : static int setsize(unsigned long capacity, unsigned int *cyls, unsigned int *hds,
      26                 :            :                    unsigned int *secs);
      27                 :            : 
      28                 :            : /**
      29                 :            :  * scsi_bios_ptable - Read PC partition table out of first sector of device.
      30                 :            :  * @dev: from this device
      31                 :            :  *
      32                 :            :  * Description: Reads the first sector from the device and returns %0x42 bytes
      33                 :            :  *              starting at offset %0x1be.
      34                 :            :  * Returns: partition table in kmalloc(GFP_KERNEL) memory, or NULL on error.
      35                 :            :  */
      36                 :          0 : unsigned char *scsi_bios_ptable(struct block_device *dev)
      37                 :            : {
      38                 :            :         unsigned char *res = kmalloc(66, GFP_KERNEL);
      39                 :          0 :         if (res) {
      40                 :          0 :                 struct block_device *bdev = dev->bd_contains;
      41                 :            :                 Sector sect;
      42                 :          0 :                 void *data = read_dev_sector(bdev, 0, &sect);
      43                 :          0 :                 if (data) {
      44                 :          0 :                         memcpy(res, data + 0x1be, 66);
      45                 :            :                         put_dev_sector(sect);
      46                 :            :                 } else {
      47                 :          0 :                         kfree(res);
      48                 :            :                         res = NULL;
      49                 :            :                 }
      50                 :            :         }
      51                 :          0 :         return res;
      52                 :            : }
      53                 :            : EXPORT_SYMBOL(scsi_bios_ptable);
      54                 :            : 
      55                 :            : /**
      56                 :            :  * scsicam_bios_param - Determine geometry of a disk in cylinders/heads/sectors.
      57                 :            :  * @bdev: which device
      58                 :            :  * @capacity: size of the disk in sectors
      59                 :            :  * @ip: return value: ip[0]=heads, ip[1]=sectors, ip[2]=cylinders
      60                 :            :  *
      61                 :            :  * Description : determine the BIOS mapping/geometry used for a drive in a
      62                 :            :  *      SCSI-CAM system, storing the results in ip as required
      63                 :            :  *      by the HDIO_GETGEO ioctl().
      64                 :            :  *
      65                 :            :  * Returns : -1 on failure, 0 on success.
      66                 :            :  */
      67                 :            : 
      68                 :          0 : int scsicam_bios_param(struct block_device *bdev, sector_t capacity, int *ip)
      69                 :            : {
      70                 :            :         unsigned char *p;
      71                 :            :         u64 capacity64 = capacity;      /* Suppress gcc warning */
      72                 :            :         int ret;
      73                 :            : 
      74                 :          0 :         p = scsi_bios_ptable(bdev);
      75                 :          0 :         if (!p)
      76                 :            :                 return -1;
      77                 :            : 
      78                 :            :         /* try to infer mapping from partition table */
      79                 :          0 :         ret = scsi_partsize(p, (unsigned long)capacity, (unsigned int *)ip + 2,
      80                 :            :                                (unsigned int *)ip + 0, (unsigned int *)ip + 1);
      81                 :          0 :         kfree(p);
      82                 :            : 
      83                 :          0 :         if (ret == -1 && capacity64 < (1ULL << 32)) {
      84                 :            :                 /* pick some standard mapping with at most 1024 cylinders,
      85                 :            :                    and at most 62 sectors per track - this works up to
      86                 :            :                    7905 MB */
      87                 :            :                 ret = setsize((unsigned long)capacity, (unsigned int *)ip + 2,
      88                 :            :                        (unsigned int *)ip + 0, (unsigned int *)ip + 1);
      89                 :            :         }
      90                 :            : 
      91                 :            :         /* if something went wrong, then apparently we have to return
      92                 :            :            a geometry with more than 1024 cylinders */
      93                 :          0 :         if (ret || ip[0] > 255 || ip[1] > 63) {
      94                 :          0 :                 if ((capacity >> 11) > 65534) {
      95                 :          0 :                         ip[0] = 255;
      96                 :          0 :                         ip[1] = 63;
      97                 :            :                 } else {
      98                 :          0 :                         ip[0] = 64;
      99                 :          0 :                         ip[1] = 32;
     100                 :            :                 }
     101                 :            : 
     102                 :          0 :                 if (capacity > 65535*63*255)
     103                 :          0 :                         ip[2] = 65535;
     104                 :            :                 else
     105                 :          0 :                         ip[2] = (unsigned long)capacity / (ip[0] * ip[1]);
     106                 :            :         }
     107                 :            : 
     108                 :            :         return 0;
     109                 :            : }
     110                 :            : EXPORT_SYMBOL(scsicam_bios_param);
     111                 :            : 
     112                 :            : /**
     113                 :            :  * scsi_partsize - Parse cylinders/heads/sectors from PC partition table
     114                 :            :  * @buf: partition table, see scsi_bios_ptable()
     115                 :            :  * @capacity: size of the disk in sectors
     116                 :            :  * @cyls: put cylinders here
     117                 :            :  * @hds: put heads here
     118                 :            :  * @secs: put sectors here
     119                 :            :  *
     120                 :            :  * Determine the BIOS mapping/geometry used to create the partition
     121                 :            :  * table, storing the results in @cyls, @hds, and @secs
     122                 :            :  *
     123                 :            :  * Returns: -1 on failure, 0 on success.
     124                 :            :  */
     125                 :            : 
     126                 :          0 : int scsi_partsize(unsigned char *buf, unsigned long capacity,
     127                 :            :                unsigned int *cyls, unsigned int *hds, unsigned int *secs)
     128                 :            : {
     129                 :            :         struct partition *p = (struct partition *)buf, *largest = NULL;
     130                 :            :         int i, largest_cyl;
     131                 :            :         int cyl, ext_cyl, end_head, end_cyl, end_sector;
     132                 :            :         unsigned int logical_end, physical_end, ext_physical_end;
     133                 :            : 
     134                 :            : 
     135                 :          0 :         if (*(unsigned short *) (buf + 64) == 0xAA55) {
     136                 :          0 :                 for (largest_cyl = -1, i = 0; i < 4; ++i, ++p) {
     137                 :          0 :                         if (!p->sys_ind)
     138                 :          0 :                                 continue;
     139                 :            : #ifdef DEBUG
     140                 :            :                         printk("scsicam_bios_param : partition %d has system \n",
     141                 :            :                                i);
     142                 :            : #endif
     143                 :          0 :                         cyl = p->cyl + ((p->sector & 0xc0) << 2);
     144                 :          0 :                         if (cyl > largest_cyl) {
     145                 :            :                                 largest_cyl = cyl;
     146                 :            :                                 largest = p;
     147                 :            :                         }
     148                 :            :                 }
     149                 :            :         }
     150                 :          0 :         if (largest) {
     151                 :          0 :                 end_cyl = largest->end_cyl + ((largest->end_sector & 0xc0) << 2);
     152                 :          0 :                 end_head = largest->end_head;
     153                 :          0 :                 end_sector = largest->end_sector & 0x3f;
     154                 :            : 
     155                 :          0 :                 if (end_head + 1 == 0 || end_sector == 0)
     156                 :            :                         return -1;
     157                 :            : 
     158                 :            : #ifdef DEBUG
     159                 :            :                 printk("scsicam_bios_param : end at h = %d, c = %d, s = %d\n",
     160                 :            :                        end_head, end_cyl, end_sector);
     161                 :            : #endif
     162                 :            : 
     163                 :          0 :                 physical_end = end_cyl * (end_head + 1) * end_sector +
     164                 :          0 :                     end_head * end_sector + end_sector;
     165                 :            : 
     166                 :            :                 /* This is the actual _sector_ number at the end */
     167                 :          0 :                 logical_end = get_unaligned_le32(&largest->start_sect)
     168                 :            :                     + get_unaligned_le32(&largest->nr_sects);
     169                 :            : 
     170                 :            :                 /* This is for >1023 cylinders */
     171                 :          0 :                 ext_cyl = (logical_end - (end_head * end_sector + end_sector))
     172                 :          0 :                     / (end_head + 1) / end_sector;
     173                 :          0 :                 ext_physical_end = ext_cyl * (end_head + 1) * end_sector +
     174                 :          0 :                     end_head * end_sector + end_sector;
     175                 :            : 
     176                 :            : #ifdef DEBUG
     177                 :            :                 printk("scsicam_bios_param : logical_end=%d physical_end=%d ext_physical_end=%d ext_cyl=%d\n"
     178                 :            :                   ,logical_end, physical_end, ext_physical_end, ext_cyl);
     179                 :            : #endif
     180                 :            : 
     181                 :          0 :                 if ((logical_end == physical_end) ||
     182                 :          0 :                   (end_cyl == 1023 && ext_physical_end == logical_end)) {
     183                 :          0 :                         *secs = end_sector;
     184                 :          0 :                         *hds = end_head + 1;
     185                 :          0 :                         *cyls = capacity / ((end_head + 1) * end_sector);
     186                 :          0 :                         return 0;
     187                 :            :                 }
     188                 :            : #ifdef DEBUG
     189                 :            :                 printk("scsicam_bios_param : logical (%u) != physical (%u)\n",
     190                 :            :                        logical_end, physical_end);
     191                 :            : #endif
     192                 :            :         }
     193                 :            :         return -1;
     194                 :            : }
     195                 :            : EXPORT_SYMBOL(scsi_partsize);
     196                 :            : 
     197                 :            : /*
     198                 :            :  * Function : static int setsize(unsigned long capacity,unsigned int *cyls,
     199                 :            :  *      unsigned int *hds, unsigned int *secs);
     200                 :            :  *
     201                 :            :  * Purpose : to determine a near-optimal int 0x13 mapping for a
     202                 :            :  *      SCSI disk in terms of lost space of size capacity, storing
     203                 :            :  *      the results in *cyls, *hds, and *secs.
     204                 :            :  *
     205                 :            :  * Returns : -1 on failure, 0 on success.
     206                 :            :  *
     207                 :            :  * Extracted from
     208                 :            :  *
     209                 :            :  * WORKING                                                    X3T9.2
     210                 :            :  * DRAFT                                                        792D
     211                 :            :  * see http://www.t10.org/ftp/t10/drafts/cam/cam-r12b.pdf
     212                 :            :  *
     213                 :            :  *                                                        Revision 6
     214                 :            :  *                                                         10-MAR-94
     215                 :            :  * Information technology -
     216                 :            :  * SCSI-2 Common access method
     217                 :            :  * transport and SCSI interface module
     218                 :            :  * 
     219                 :            :  * ANNEX A :
     220                 :            :  *
     221                 :            :  * setsize() converts a read capacity value to int 13h
     222                 :            :  * head-cylinder-sector requirements. It minimizes the value for
     223                 :            :  * number of heads and maximizes the number of cylinders. This
     224                 :            :  * will support rather large disks before the number of heads
     225                 :            :  * will not fit in 4 bits (or 6 bits). This algorithm also
     226                 :            :  * minimizes the number of sectors that will be unused at the end
     227                 :            :  * of the disk while allowing for very large disks to be
     228                 :            :  * accommodated. This algorithm does not use physical geometry. 
     229                 :            :  */
     230                 :            : 
     231                 :            : static int setsize(unsigned long capacity, unsigned int *cyls, unsigned int *hds,
     232                 :            :                    unsigned int *secs)
     233                 :            : {
     234                 :            :         unsigned int rv = 0;
     235                 :            :         unsigned long heads, sectors, cylinders, temp;
     236                 :            : 
     237                 :            :         cylinders = 1024L;      /* Set number of cylinders to max */
     238                 :            :         sectors = 62L;          /* Maximize sectors per track */
     239                 :            : 
     240                 :            :         temp = cylinders * sectors;     /* Compute divisor for heads */
     241                 :          0 :         heads = capacity / temp;        /* Compute value for number of heads */
     242                 :          0 :         if (capacity % temp) {  /* If no remainder, done! */
     243                 :          0 :                 heads++;        /* Else, increment number of heads */
     244                 :          0 :                 temp = cylinders * heads;       /* Compute divisor for sectors */
     245                 :          0 :                 sectors = capacity / temp;      /* Compute value for sectors per
     246                 :            :                                                    track */
     247                 :          0 :                 if (capacity % temp) {  /* If no remainder, done! */
     248                 :          0 :                         sectors++;      /* Else, increment number of sectors */
     249                 :          0 :                         temp = heads * sectors;         /* Compute divisor for cylinders */
     250                 :          0 :                         cylinders = capacity / temp;    /* Compute number of cylinders */
     251                 :            :                 }
     252                 :            :         }
     253                 :          0 :         if (cylinders == 0)
     254                 :            :                 rv = (unsigned) -1;     /* Give error if 0 cylinders */
     255                 :            : 
     256                 :          0 :         *cyls = (unsigned int) cylinders;       /* Stuff return values */
     257                 :          0 :         *secs = (unsigned int) sectors;
     258                 :          0 :         *hds = (unsigned int) heads;
     259                 :          0 :         return (rv);
     260                 :            : }