Newbie question about usage of mmap
Hi there,
I have a PCI device and I tried to write a short code to access it in user space with mmap.
first I "cat /proc/bus/pci/devices" and get the device's address: 0x00001800.
then I write the following code:
#include <sys/mman.h>
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <string.h>
int main(void)
{
void *map;
int fd;
int src = 0;
ulong base;
ulong length;
base = 0x00001800;
length = 0xFF;
fd = open("/dev/mem", O_RDWR);
printf("%d\n",fd);
map = mmap(NULL, (size_t)length, (PROT_READ | PROT_WRITE), MAP_SHARED, fd,(off_t)base);
if (map == MAP_FAILED)
{
printf("map failed: %s\n",strerror(errno));
exit(1);
}
memcpy(map+0x85,&src, 1);
return 0;
}
I run the code and got the error says that "Invalid Argument", I guess that is because of some misuse of mmap, but where is the error?
TIA
justin
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