minix/servers/fs/cdprobe.c

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/* This file contains some code to guess where we have to load the
* RAM image device from, if started from CD. (In this case it's hard
* to tell where this is without diving into BIOS heuristics.)
*
* There is some nasty hard-codery in here (e.g. AT minor device numbers,
* MINIX cd label) that can be improved on.
*
* Changes:
* Jul 14, 2005 Created (Ben Gras)
*/
#include "fs.h"
#include "super.h"
#include <minix/com.h>
#include <string.h>
/*===========================================================================*
* cdprobe *
*===========================================================================*/
PUBLIC int cdprobe(void)
{
#define CD_SECTOR 2048
#define AT_MAJOR 3
#define AT_MINORS 4
int i, minors[AT_MINORS] = { 0, 5, 10, 15 }, dev = 0, found = 0;
char pvd[CD_SECTOR];
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printf("\nLooking for boot CD. This may take a minute.\n"
"Please ignore any error messages.\n\n");
for(i = 0; i < AT_MINORS && !found; i++) {
struct super_block probe_super;
int r, minor;
dev = (AT_MAJOR << MAJOR) | minors[i];
/* Open device readonly. (This fails if the device
* is also writable, which a CD isn't.)
*/
if((r = dev_open(dev, FS_PROC_NR, RO_BIT)) != OK) {
continue;
}
if((r = dev_io(DEV_READ, dev, FS_PROC_NR, pvd,
16*CD_SECTOR, sizeof(pvd), 0)) != sizeof(pvd)) {
dev_close(dev);
continue;
}
dev_close(dev);
/* Check PVD ID. */
if(pvd[0] != 1 || pvd[1] != 'C' || pvd[2] != 'D' ||
pvd[3] != '0' || pvd[4] != '0' || pvd[5] != '1' || pvd[6] != 1 ||
strncmp(pvd + 40, "MINIX", 5)) {
continue;
}
/* 3. Both c0dXp1 and p2 should have a superblock. */
for(minor = minors[i]+2; minor <= minors[i]+3; minor++) {
dev = (AT_MAJOR << MAJOR) | minor;
if((r = dev_open(dev, FS_PROC_NR, R_BIT)) != OK) {
break;
}
probe_super.s_dev = dev;
r = read_super(&probe_super);
dev_close(dev);
if(r != OK) {
break;
}
}
if(minor > minors[i]+3) {
/* Success? Then set dev to p1. */
dev = (AT_MAJOR << MAJOR) | (minors[i]+2);
found = 1;
break;
}
}
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if(!found) return NO_DEV;
return dev;
}