pwm2.c

来自「fsmlabs的real time linux的内核」· C语言 代码 · 共 145 行

/* vim: set ts=4: */
/*
 * Copywrite 2002 Der Herr Hofrat
 * License GPL V2
 * Author [e-mail]
 */
/*
 * example of a simple PWM using a proc interface to set the duty cylcle
 */
#include <rtl.h>
#include <time.h>
#include <rtl_sched.h>
#include <rtl_sync.h>
#include <pthread.h>
#include <posix/unistd.h>

#include <linux/proc_fs.h> /* proc filesystem stuff */
struct proc_dir_entry *proc_pwm_duty_cycle;

#include <asm/io.h> /* outb */
#define LPT 0x378
#define LPT_CNTRL LPT+2 

#define MAX_DUTY_CYCLE 90
#define MIN_DUTY_CYCLE 10
#define DC_SCALAR 10000 /* 10 micro seconds */
#define PERIOD 100*DC_SCALAR /* period is 100% duty cycle */

pthread_t pwm_thread;
void *pwm_code(void *);
int stop = 0;
unsigned long duty_cycle=MIN_DUTY_CYCLE*DC_SCALAR;

int simple_atoi(const char *);
#define MAXLEN 3  /* maximum number of digits to use */

void *pwm_code(void *arg){
	struct timespec t;
	clock_gettime(CLOCK_REALTIME,&t);

	while(!stop){

		outb(0x0,LPT);
		timespec_add_ns(&t,PERIOD-duty_cycle);
		clock_nanosleep(CLOCK_REALTIME, TIMER_ABSTIME, &t, NULL);

		outb(0xff,LPT);
		timespec_add_ns(&t,duty_cycle);
		clock_nanosleep(CLOCK_REALTIME, TIMER_ABSTIME, &t, NULL);
	}

	return (void *)stop;
}

int 
get_duty_cycle(
	char *page,
	char **start, 
	off_t off, 
	int count,
	int *eof, 
	void *data)
{
	int size = 0;
    
	MOD_INC_USE_COUNT;
	
	size+=sprintf(page+size,"Duty Cycle:%d %%\n",(int)duty_cycle/DC_SCALAR);

	MOD_DEC_USE_COUNT;
	return(size);
}

static int 
set_duty_cycle(
	struct file *file, 
	const char *user_buffer,
	unsigned long count, 
	void *data)
{
	MOD_INC_USE_COUNT;

	duty_cycle=simple_atoi(user_buffer)*DC_SCALAR;
	printk("duty_cylce set to %ld\n",duty_cycle);

	MOD_DEC_USE_COUNT;
	return count;
}

int init_module(void){

	proc_pwm_duty_cycle = create_proc_entry("pwm_duty_cycle",
        S_IFREG | S_IWUSR,
        &proc_root);

	proc_pwm_duty_cycle->read_proc = get_duty_cycle;
	proc_pwm_duty_cycle->write_proc = set_duty_cycle;

	if(pthread_create(&pwm_thread,NULL,pwm_code,NULL))
	{
		printk("Pthread_create failed\n");
		return -1; 
	}
	return 0;
}

void cleanup_module(void){ 
	stop = 1;
	pthread_join(pwm_thread,NULL);
    remove_proc_entry("thread_status", &proc_root);
}

int 
simple_atoi(const char * number)
{
	int i;
	int retval=0;
	int len = strnlen(number,MAXLEN);

	/* should always do sanity checks on data passed via /proc */
	if(len>MAXLEN){
		return MIN_DUTY_CYCLE;
	}else{

		/* striped down atoi */
		for(i=0;i<len;i++){
			if(number[i]<='9' && number[i]>='0'){
				retval*=10; 
				retval+=number[i]-'0';
			}
		}

		/* bounds check on requested duty cycle */
		if(retval > MAX_DUTY_CYCLE){
			rtl_printf("Warning duty cycle requested was out of bounds\n");
			return MAX_DUTY_CYCLE;
		} else if(retval < MIN_DUTY_CYCLE){
			rtl_printf("Warning duty cycle requested was out of bounds\n");
			return MIN_DUTY_CYCLE;
		} else
			return retval;

	}
}