using map_user_kiobuf

[Oliver Ryan <oryan@physics.nuigalway.ie>]

Hi all,

I found the following piece of code below (from 
http://www.linuxarkivet.nu/mlists/linux-kernel/0011/msg05179.html) and 
would like to use it but I don't understand all of it:

1.  if test_kiobuf(char *buf) is a kernel module, how is it compiled and 
linked with the user space program?  How can buf be passed into it?  Where 
would init_module come into it?

2.  In the user space program, what is the ioctl command number 99 stand 
for?  I haven't found it anywhere.  What is that line (ioctl(fh, 99, buf)) 
doing?

That's it.  Thanks in advance for any help.

Oliver.

int test_kiobuf(char* buf)
{
struct kiobuf *iobuf;
int i;
alloc_kiovec(1, &iobuf);
 map_user_kiobuf(WRITE, iobuf, buf, TEST_SIZE);
 for (i = 0 ; i < iobuf->length; i++)
{
int off = iobuf->offset + i;
int page = off / 4096;
unsigned char* buf = page_address(iobuf->maplist[page]);
buf[off % 4096] = (i & 0xFF); }
 unmap_kiobuf(iobuf);
free_kiovec(1, &iobuf);
 return 0; }

The user space programme is:
#include <stdio.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#define TEST_SIZE 1000000
int main(int argc, char *argv[])
{
 int fh;
int i;
unsigned char * buf;
buf = (unsigned char *)malloc(TEST_SIZE);
fh = open("/tmp/test", O_CREAT);
if (ioctl(fh, 99, buf) != 0)
  perror("ioctl failed");
else
  {
    for (i = 0; i < TEST_SIZE; i++)
     {
        if (buf[i] != (i & 0xFF))
          printf("%8.8X: %2.2X %2.2X\n", i, i & 0xFF, buf[i]);
       }
   }
   close(fh);
  free(buf);
  return 0; }

.




Dept. of Physics,
National University of Ireland, Galway,
Galway,
Ireland.

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