/*
 * eppconfig.c
 *
 * This is part of ppa3 package.
 * Use this program to configure EPP speed.
 *
 * Get the address of the ppa_epp_speed from startup log, something like:
 * ppa0: ppa_epp_speed = 10000 at 0xf01c1a30
 *
 * Then use eppconfig like this:
 *
 *	$ eppconfig 0x<hexadecimal address> <decimal value>
 *
 * Of course, DO NOT USE ANY OTHER ADDRESS. eppconfig writes directly to
 * the device /dev/kmem to update the value.
 *
 * EPP timeouts are generated by the port because the drive is too slow.
 * EPP timeouts are avoided in ppa3.c with a DELAY(). epp_speed is the
 * duration of this delay. Then EPP timeouts are lost CPU time.
 */

#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>

#define EPP_VERSION "1.0"
#define PPA_VERSION "0.62-BETA"

#define DEV_MEM "/dev/kmem"

void usage (int argc, char ** argv) {

	fprintf (stderr, "usage: %s <address> <value>\n", argv[0]);

	return;
} /* usage */

int open_mem (void) {

	int dev;

	dev = open (DEV_MEM, O_RDWR);
	if (dev < 0) {
		perror ("open");
		exit (1);
	}

	return dev;
} /* open_mem */

int read_value (int dev, unsigned int address) {

	int value;

	if (lseek (dev, address, SEEK_SET) < 0) {
		perror ("lseek");
		exit (1);
	}
	if (read (dev, &value, sizeof (int)) < 0) {
		perror ("read");
		exit (1);
	}
	
	return value;
} /* read_value */

void write_value (int dev, unsigned int address, int value) {

	if (lseek (dev, address, SEEK_SET) < 0) {
		perror ("lseek");
		exit (1);
	}
	if (write (dev, &value, sizeof (int)) < 0) {
		perror ("read");
		exit (1);
	}

	return;
} /* write_value */

void main (int argc, char ** argv) {

	unsigned int address;
	int oldv, newv, dev;

	if (argc != 3) {
		usage (argc, argv);
		exit (1);
	}

	if (sscanf (argv[1], "0x%x", &address) != 1 || 
		sscanf (argv[2], "%d", &newv) != 1) {
		usage (argc, argv);
		exit (1);
	}

	printf ("eppconfig version %s to use with PPA3 driver release %s.\n",
		EPP_VERSION, PPA_VERSION);

	dev = open_mem ();

	oldv = read_value (dev, address);
	printf ("Old value: %d at 0x%x\n", oldv, address);

	write_value (dev, address, newv);

	newv = read_value (dev, address);
	printf ("New value: %d at 0x%x\n", newv, address);

	exit (0);
} /* main */