write_dev_mem.c

来自「fsmlabs的real time linux的内核」· C语言 代码 · 共 56 行

/*
 * Written by Der Herr Hofrat, [e-mail]
 * (C) 2002 FSMLabs
 * License: GPL Version 2
 */
/*
 *  Example of write access to shared memory from user-space
 */

#include <stdlib.h>
#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/mman.h>

#include "hello.h"

struct shared_mem_struct* shared_mem;
int memfd;

int main()
{
	char input[40];
	char stop=0;

	memfd = open("/dev/mem", O_RDWR);
	if (memfd){
		shared_mem = (struct shared_mem_struct*) mmap(0,
	  		sizeof(struct shared_mem_struct),
	  		PROT_READ | PROT_WRITE, 
			MAP_FILE | MAP_SHARED, 
			memfd, 
			MEMORY_OFFSET);
		if(shared_mem != NULL){
			printf("enter integer value to put in sahred memory - <quit> to exit\n");
			do{
				scanf("%s", input);
				shared_mem->some_int = atoi(input);
				shared_mem->ready = 1;
			}while (strcmp("quit",input));
		}
		else{
			printf("Failed to map memory\n");
			close (memfd);
			exit(-1);
		}
	}
	else{
		printf("Failed to open memory device file\n");
		exit(-1);
	}

	close(memfd);
	return 0;
}