drivers/auxdisplay/ks0108.c

/*
 *    Filename: ks0108.c
 *     Version: 0.1.0
 * Description: ks0108 LCD Controller driver
 *     License: GPLv2
 *     Depends: parport
 *
 *      Author: Copyright (C) Miguel Ojeda Sandonis
 *        Date: 2006-10-31
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License version 2 as
 *  published by the Free Software Foundation.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/init.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/delay.h>
#include <linux/fs.h>
#include <linux/io.h>
#include <linux/parport.h>
#include <linux/uaccess.h>
#include <linux/ks0108.h>

#define KS0108_NAME "ks0108"

/*
 * Module Parameters
 */

static unsigned int ks0108_port = CONFIG_KS0108_PORT;
module_param(ks0108_port, uint, S_IRUGO);
MODULE_PARM_DESC(ks0108_port, "Parallel port where the LCD is connected");

static unsigned int ks0108_delay = CONFIG_KS0108_DELAY;
module_param(ks0108_delay, uint, S_IRUGO);
MODULE_PARM_DESC(ks0108_delay, "Delay between each control writing (microseconds)");

/*
 * Device
 */

static struct parport *ks0108_parport;
static struct pardevice *ks0108_pardevice;

/*
 * ks0108 Exported Commands (don't lock)
 *
 *   You _should_ lock in the top driver: This functions _should not_
 *   get race conditions in any way. Locking for each byte here would be
 *   so slow and useless.
 *
 *   There are not bit definitions because they are not flags,
 *   just arbitrary combinations defined by the documentation for each
 *   function in the ks0108 LCD controller. If you want to know what means
 *   a specific combination, look at the function's name.
 *
 *   The ks0108_writecontrol bits need to be reverted ^(0,1,3) because
 *   the parallel port also revert them using a "not" logic gate.
 */

#define bit(n) (((unsigned char)1)<<(n))

void ks0108_writedata(unsigned char byte)
{
	parport_write_data(ks0108_parport, byte);
}

void ks0108_writecontrol(unsigned char byte)
{
	udelay(ks0108_delay);
	parport_write_control(ks0108_parport, byte ^ (bit(0) | bit(1) | bit(3)));
}

void ks0108_displaystate(unsigned char state)
{
	ks0108_writedata((state ? bit(0) : 0) | bit(1) | bit(2) | bit(3) | bit(4) | bit(5));
}

void ks0108_startline(unsigned char startline)
{
	ks0108_writedata(min_t(unsigned char, startline, 63) | bit(6) |
			 bit(7));
}

void ks0108_address(unsigned char address)
{
	ks0108_writedata(min_t(unsigned char, address, 63) | bit(6));
}

void ks0108_page(unsigned char page)
{
	ks0108_writedata(min_t(unsigned char, page, 7) | bit(3) | bit(4) |
			 bit(5) | bit(7));
}

EXPORT_SYMBOL_GPL(ks0108_writedata);
EXPORT_SYMBOL_GPL(ks0108_writecontrol);
EXPORT_SYMBOL_GPL(ks0108_displaystate);
EXPORT_SYMBOL_GPL(ks0108_startline);
EXPORT_SYMBOL_GPL(ks0108_address);
EXPORT_SYMBOL_GPL(ks0108_page);

/*
 * Is the module inited?
 */

static unsigned char ks0108_inited;
unsigned char ks0108_isinited(void)
{
	return ks0108_inited;
}
EXPORT_SYMBOL_GPL(ks0108_isinited);

/*
 * Module Init & Exit
 */

static int __init ks0108_init(void)
{
	int result;
	int ret = -EINVAL;

	ks0108_parport = parport_find_base(ks0108_port);
	if (ks0108_parport == NULL) {
		pr_err("ERROR: parport didn't find %i port\n", ks0108_port);
		goto none;
	}

	ks0108_pardevice = parport_register_device(ks0108_parport, KS0108_NAME,
		NULL, NULL, NULL, PARPORT_DEV_EXCL, NULL);
	parport_put_port(ks0108_parport);
	if (ks0108_pardevice == NULL) {
		pr_err("ERROR: parport didn't register new device\n");
		goto none;
	}

	result = parport_claim(ks0108_pardevice);
	if (result != 0) {
		pr_err("ERROR: can't claim %i parport, maybe in use\n",
		       ks0108_port);
		ret = result;
		goto registered;
	}

	ks0108_inited = 1;
	return 0;

registered:
	parport_unregister_device(ks0108_pardevice);

none:
	return ret;
}

static void __exit ks0108_exit(void)
{
	parport_release(ks0108_pardevice);
	parport_unregister_device(ks0108_pardevice);
}

module_init(ks0108_init);
module_exit(ks0108_exit);

MODULE_LICENSE("GPL v2");
MODULE_AUTHOR("Miguel Ojeda Sandonis <miguel.ojeda.sandonis@gmail.com>");
MODULE_DESCRIPTION("ks0108 LCD Controller driver");