50 lines
1.2 KiB
C
50 lines
1.2 KiB
C
|
/* Peek and poke using /dev/mem.
|
||
|
|
*
|
||
|
|
* Callers now ought to check the return values.
|
||
|
|
*
|
||
|
|
* Calling peek() requires read permission on /dev/mem, and consumes
|
||
|
|
* a file descriptor. Calling poke() requires write permission, and
|
||
|
|
* consumes another file descriptor.
|
||
|
|
*/
|
||
|
|
|
||
|
|
#include <sys/types.h>
|
||
|
|
#include <fcntl.h>
|
||
|
|
#include <unistd.h>
|
||
|
|
|
||
|
|
_PROTOTYPE( int peek, (unsigned segment, unsigned offset));
|
||
|
|
_PROTOTYPE( int poke, (unsigned segment, unsigned offset, unsigned value));
|
||
|
|
|
||
|
|
#define SEGSIZE 0x10
|
||
|
|
|
||
|
|
int peek(segment, offset)
|
||
|
|
unsigned segment;
|
||
|
|
unsigned offset;
|
||
|
|
{
|
||
|
|
unsigned char chvalue;
|
||
|
|
static int infd = -1;
|
||
|
|
|
||
|
|
if (infd < 0) infd = open("/dev/mem", O_RDONLY);
|
||
|
|
if (infd < 0 ||
|
||
|
|
lseek(infd, (unsigned long) segment * SEGSIZE + offset, SEEK_SET) < 0 ||
|
||
|
|
read(infd, (char *) &chvalue, (unsigned) 1) != 1)
|
||
|
|
return(-1);
|
||
|
|
return(chvalue);
|
||
|
|
}
|
||
|
|
|
||
|
|
int poke(segment, offset, value)
|
||
|
|
unsigned segment;
|
||
|
|
unsigned offset;
|
||
|
|
unsigned value;
|
||
|
|
{
|
||
|
|
unsigned char chvalue;
|
||
|
|
static int outfd = -1;
|
||
|
|
|
||
|
|
chvalue = value;
|
||
|
|
if (outfd < 0) outfd = open("/dev/mem", O_WRONLY);
|
||
|
|
if (outfd < 0 ||
|
||
|
|
lseek(outfd, (unsigned long) segment * SEGSIZE + offset, SEEK_SET) < 0 ||
|
||
|
|
write(outfd, (char *) &chvalue, (unsigned) 1) != 1)
|
||
|
|
return(-1);
|
||
|
|
return(chvalue);
|
||
|
|
}
|