>I know this subject has been beaten to death but I can't seem to get it to go on my
>system.
>[snip]
>Garth Gaddy
Hi Garth,
Nice to meet you at the show, I looked at your code, and I can't see
anything obviously wrong.
I have attached a stand alone test program that gives a simple example
of using shared memory. I tested it on rtl 0.9j+ (1.0) and 2.0.36. You
may need to change the -I in the makefile and some hash defines for the
size of memory on your system.
Details of how to use it are in the source header.
I hope this works for you.
Regards
Stuart.
-
Visit http://www.zentropix.com/ for Real Time Linux Tools
////////////////////////////////////////////////////////////////////////////////
//
// Copyright © 1998 Zentropic Computing, All rights reserved
//
// Authors: Stuart Hughes
// Original date: Mon 16 Aug 1999
// Id: @(#)$Id$
// License: GPL
//
// Description: This is an example that shows how to set up shared
// memory under real time Linux to allow access
// from both user and real time context. Build it by
// typing "make -f Makefile.shm", to run the program,
// do an insmod of rtl_sched, and shm_rt. Next run
// ./shm. If it is working, you should see an
// incrementing number printed at the tty.
//
// Scheme The user space loop increments a counter in shared
// memory, this location is copied in the real-time
// task (asynchronously) to another shared memory
// location. The user space print the contents of
// the shared memory location written to by the
// real time task.
//
// Variables Shared memory is reserved by adding a line like
// append="mem=63m" (example to reserve 1 meg in a
// 64 meg machine)
// The include path for RTL may need chaning in the
// Makefile.shm for your system
//
// Notes: For 2.2 kernels you need to uses ioremap and iounmap
// in place of vremap and vfree.
// Error checking omitted for clarity.
//
//
////////////////////////////////////////////////////////////////////////////////
static char id_shm_c[] __attribute__ ((unused)) = "@(#)$Id$";
// change this line if you have a different memory size
#define SHM_BASE ((63 * 0x100000))
struct shm_vars
{
int from_user;
int to_user;
};
struct shm_vars *shm_ptr;
///////////////////////////////////////////////////////////////////////////////
//
// kernel module
//
///////////////////////////////////////////////////////////////////////////////
#ifdef __KERNEL__
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <rtl_sched.h>
RT_TASK task_str;
void func(int arg)
{
while(1) {
shm_ptr->to_user = shm_ptr->from_user;
rt_task_wait();
}
}
int init_module(void)
{
shm_ptr = (struct shm_vars *) vremap(SHM_BASE, sizeof(struct shm_vars));
shm_ptr->from_user = shm_ptr->to_user = 0;
rt_task_init(&task_str, func, 0, 3000, 4);
rt_task_make_periodic(&task_str, rt_get_time(), (RT_TICKS_PER_SEC/10000));
return 0;
}
void cleanup_module(void)
{
rt_task_suspend(&task_str);
rt_task_delete(&task_str);
vfree(shm_ptr);
}
///////////////////////////////////////////////////////////////////////////////
//
// user process
//
///////////////////////////////////////////////////////////////////////////////
#else
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <sys/mman.h>
#include <fcntl.h>
#include <errno.h>
int main()
{
int mem_fd;
if(( mem_fd = open("/dev/mem", O_RDWR)) < 0) {
printf("open(/dev/mem, O_RDWR) : %s\n", strerror(errno));
exit(1);
}
shm_ptr = (struct shm_vars *) mmap(0,
sizeof(struct shm_vars),
PROT_READ | PROT_WRITE,
MAP_FILE | MAP_SHARED,
mem_fd,
SHM_BASE );
if( shm_ptr == MAP_FAILED ) {
printf("mmap failed: %s\n", strerror(errno));
exit(1);
}
close(mem_fd);
// main loop, update counter, read back and print copy from RT
while(1) {
shm_ptr->from_user++;
printf("counter = %d\n", shm_ptr->to_user);
usleep(100000);
}
}
#endif
# you will need to change this
INC = -I /usr/src/rtl/include
all: shm shm_rt
shm_rt: shm.c
gcc $(INC) -D__RT__ -D__KERNEL__ -DMODULE -O2 -g -c -o shm_rt.o shm.c
ld -r -static -o shm_rt shm_rt.o
rm shm_rt.o
clean:
rm shm shm.o shm_rt shm_rt.o
