cdprobe.c

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    1 /* This file contains some code to guess where we have to load the
    2  * RAM image device from, if started from CD. (In this case it's hard
    3  * to tell where this is without diving into BIOS heuristics.)
    4  *
    5  * There is some nasty hard-codery in here (e.g. AT minor device numbers,
    6  * MINIX cd label) that can be improved on.
    7  *
    8  * Changes:
    9  *   Jul 14, 2005   Created (Ben Gras)
   10  */
   11 
   12 #include "fs.h"
   13 #include "super.h"
   14 
   15 #include <minix/com.h>
   16 #include <string.h>
   17 
   18 /*===========================================================================*
   19  *                              cdprobe                                      *
   20  *===========================================================================*/
   21 PUBLIC int cdprobe(void)
   22 {
   23 #define CD_SECTOR       2048
   24 #define AT_MAJOR        3
   25 #define AT_MINORS       4
   26         int i, minors[AT_MINORS] = { 0, 5, 10, 15 }, dev = 0, found = 0;
   27         char pvd[CD_SECTOR];
   28         printf("\nLooking for boot CD. This may take a minute.\n"
   29                 "Please ignore any error messages.\n\n");
   30         for(i = 0; i < AT_MINORS && !found; i++) {
   31                 struct super_block probe_super;
   32                 int r, minor;
   33 
   34                 dev = (AT_MAJOR << MAJOR) | minors[i];
   35 
   36                 /* Open device readonly. (This fails if the device
   37                  * is also writable, which a CD isn't.)
   38                  */
   39                 if ((r = dev_open(dev, FS_PROC_NR, RO_BIT)) != OK) {
   40                         continue;
   41                 }
   42 
   43                 if ((r = dev_io(DEV_READ, dev, FS_PROC_NR, pvd,
   44                         16*CD_SECTOR, sizeof(pvd), 0)) != sizeof(pvd)) {
   45                         dev_close(dev);
   46                         continue;
   47                 }
   48                 dev_close(dev);
   49 
   50                 /* Check PVD ID. */
   51                 if (pvd[0] !=  1  || pvd[1] != 'C' || pvd[2] != 'D' ||
   52                    pvd[3] != '' || pvd[4] != '' || pvd[5] != '1' || pvd[6] != 1 ||
   53                    strncmp(pvd + 40, "MINIX", 5)) {
   54                         continue;
   55                    }
   56 
   57                 /* 3. Both c0dXp1 and p2 should have a superblock. */
   58                 for(minor = minors[i]+2; minor <= minors[i]+3; minor++) {
   59                         dev = (AT_MAJOR << MAJOR) | minor;
   60                         if ((r = dev_open(dev, FS_PROC_NR, R_BIT)) != OK) {
   61                                 break;
   62                         }
   63                         probe_super.s_dev = dev;
   64                         r = read_super(&probe_super);
   65                         dev_close(dev);
   66                         if (r != OK) {
   67                                 break;
   68                         }
   69                 }
   70 
   71                 if (minor > minors[i]+3) {
   72                         /* Success? Then set dev to p1. */
   73                         dev = (AT_MAJOR << MAJOR) | (minors[i]+2);
   74                         found = 1;
   75                         break;
   76                 }
   77         }
   78 
   79         if (!found) return NO_DEV;
   80 
   81         return dev;
   82 }
   83

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FreeBSD/Linux Kernel Cross Reference sys/servers/fs/cdprobe.c

FreeBSD/Linux Kernel Cross Reference
sys/servers/fs/cdprobe.c