<pre>

#include <linux/module.h>
#include <linux/kernel.h>
#include <rtl_fifo.h>
#include <rtl_time.h>
#include <rtl_sched.h>
#include <asm/io.h>
#include <linux/cons.h>
#include "dpi_posixio.h"

#include <linux/soundcard.h>

#define MAX_BUFFER      16384

int buffer = 1024;
int prewrite = 0;
int fragshift = 8;
int test = 0;
MODULE_PARM(buffer,"i");
MODULE_PARM(prewrite,"i");
MODULE_PARM(fragshift,"i");
MODULE_PARM(test,"i");

char *buf;

pthread_t thread;

int fd;

int monitor(void)
{
        while(1)
        {
                if(read(fd, buf, buffer)<=0)
                        return -1;
                if(prewrite)
                {
                        /* Note: This will drop the first input buffer */
                        memset(buf, 0, prewrite);
                        write(fd, buf, prewrite);
                        prewrite = 0;
                }
                if(write(fd, buf, buffer)<=0)
                        return -1;
        }
}

int siren(void)
{
        static int a = 0;
        static int f_lo = 300<<8;
        static int f;
        static int f_hi = 500<<8;
        static int d = 1;
        int j;
        int samples;
        short *dest = (short *)buf;

samples = buffer * sizeof(char) / sizeof(dest[0]);
        f = (f_lo + f_hi) / 2;

while(1)
        {
                for(j = 0; j<samples; j+=2)
                {
                        dest[j] = a&0x7fff;
                        dest[j+1] = -a&0x7fff;
                        a+=f>>8;
                        f+=d;
                        if(f>f_hi || f<f_lo)
                                d=-d;
                }
                if(write(fd, buf, buffer)<=0)
                        return -1;
        }
}

void *thread_code(void *t)
{
        int val,r;

/*
         * This is very dangerous with the es1370 driver.
         * Wrong settings and you get a kernel panic...
         * (Can this really happen if done from user space?)
         */
        val = 0x7fff000 | (fragshift & 0xffff);
        r = ioctl(fd,SNDCTL_DSP_SETFRAGMENT,&val);
        if(r<0) goto fail;

r = ioctl(fd,SNDCTL_DSP_RESET,NULL);
        if(r<0) goto fail;
        val = 16;
        r = ioctl(fd,SNDCTL_DSP_SAMPLESIZE,&val);
        if(r<0) goto fail;
        val = AFMT_S16_LE;
        r = ioctl(fd,SNDCTL_DSP_SETFMT,&val);
        if(r<0) goto fail;
        val = 1;
        r = ioctl(fd,SNDCTL_DSP_STEREO,&val);
        if(r<0) goto fail;
        val = 44100;
        r = ioctl(fd,SNDCTL_DSP_SPEED,&val);
        if(r<0) goto fail;
        r = ioctl(fd,SNDCTL_DSP_SETDUPLEX,NULL);
        if(r<0)
        {
        fail:   rtl_printf("Failed to initialize sound device!\n");
                return (void *)-1;
        }

switch(test)
        {
        case 0:         return (void *)monitor();
        default:        return (void *)siren();
        }
}

int init_module(void)
{
        buffer &= 0xfffffffc;
        if(buffer>MAX_BUFFER)
        {
                buffer=MAX_BUFFER;
                printk("Buffer can't be bigger than %d bytes.\n", MAX_BUFFER);
                return -1;
        }

prewrite &= 0xfffffffc;
        if(prewrite>MAX_BUFFER)
        {
                prewrite=MAX_BUFFER;
                printk("Can't prewrite more than %d bytes.\n", MAX_BUFFER);
                return -1;
        }

if( !(buf = kmalloc(buffer,GFP_KERNEL)) )
        {
                printk("Couldn't allocate buffer!\n");
                return -1;
        }

if((fd = open("/dev/dsp0", O_RDWR)) < 0 )
        {
                printk("Couldn't open device! (%d)\n",fd);
                kfree(buf);
                return -1;
        }

if( pthread_create(&thread,  NULL, thread_code, (void *)1) )
        {
                printk("Failed to create RT thread!\n");
                close(fd);
                kfree(buf);
                return -1;
        }

return 0;
}

void cleanup_module(void)
{
        pthread_delete_np (thread);
        close(fd);
        kfree(buf);
}

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