i2c-parport-light.c

Go to the documentation of this file.

/* ------------------------------------------------------------------------ *
 * i2c-parport-light.c I2C bus over parallel port                           *
 * ------------------------------------------------------------------------ *
   Copyright (C) 2003-2010 Jean Delvare <[email protected]>

   Based on older i2c-velleman.c driver
   Copyright (C) 1995-2000 Simon G. Vogl
   With some changes from:
   Frodo Looijaard <[email protected]>
   Kyösti Mälkki <[email protected]>

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.

   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., 675 Mass Ave, Cambridge, MA 02139, USA.
 * ------------------------------------------------------------------------ */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/delay.h>
#include <linux/platform_device.h>
#include <linux/ioport.h>
#include <linux/i2c.h>
#include <linux/i2c-algo-bit.h>
#include <linux/i2c-smbus.h>
#include <linux/io.h>
#include "i2c-parport.h"

#define DEFAULT_BASE 0x378
#define DRVNAME "i2c-parport-light"

static struct platform_device *pdev;

static u16 base;
module_param(base, ushort, 0);
MODULE_PARM_DESC(base, "Base I/O address");

static int irq;
module_param(irq, int, 0);
MODULE_PARM_DESC(irq, "IRQ (optional)");

/* ----- Low-level parallel port access ----------------------------------- */

static inline void port_write(unsigned char p, unsigned char d)
{
    outb(d, base+p);
}

static inline unsigned char port_read(unsigned char p)
{
    return inb(base+p);
}

/* ----- Unified line operation functions --------------------------------- */

static inline void line_set(int state, const struct lineop *op)
{
    u8 oldval = port_read(op->port);

    /* Touch only the bit(s) needed */
    if ((op->inverted && !state) || (!op->inverted && state))
        port_write(op->port, oldval | op->val);
    else
        port_write(op->port, oldval & ~op->val);
}

static inline int line_get(const struct lineop *op)
{
    u8 oldval = port_read(op->port);

    return ((op->inverted && (oldval & op->val) != op->val)
        || (!op->inverted && (oldval & op->val) == op->val));
}

/* ----- I2C algorithm call-back functions and structures ----------------- */

static void parport_setscl(void *data, int state)
{
    line_set(state, &adapter_parm[type].setscl);
}

static void parport_setsda(void *data, int state)
{
    line_set(state, &adapter_parm[type].setsda);
}

static int parport_getscl(void *data)
{
    return line_get(&adapter_parm[type].getscl);
}

static int parport_getsda(void *data)
{
    return line_get(&adapter_parm[type].getsda);
}

/* Encapsulate the functions above in the correct structure
   Note that getscl will be set to NULL by the attaching code for adapters
   that cannot read SCL back */
static struct i2c_algo_bit_data parport_algo_data = {
    .setsda     = parport_setsda,
    .setscl     = parport_setscl,
    .getsda     = parport_getsda,
    .getscl     = parport_getscl,
    .udelay     = 50,
    .timeout    = HZ,
};

/* ----- Driver registration ---------------------------------------------- */

static struct i2c_adapter parport_adapter = {
    .owner      = THIS_MODULE,
    .class      = I2C_CLASS_HWMON,
    .algo_data  = &parport_algo_data,
    .name       = "Parallel port adapter (light)",
};

/* SMBus alert support */
static struct i2c_smbus_alert_setup alert_data = {
    .alert_edge_triggered   = 1,
};
static struct i2c_client *ara;
static struct lineop parport_ctrl_irq = {
    .val        = (1 << 4),
    .port       = PORT_CTRL,
};

static int __devinit i2c_parport_probe(struct platform_device *pdev)
{
    int err;

    /* Reset hardware to a sane state (SCL and SDA high) */
    parport_setsda(NULL, 1);
    parport_setscl(NULL, 1);
    /* Other init if needed (power on...) */
    if (adapter_parm[type].init.val) {
        line_set(1, &adapter_parm[type].init);
        /* Give powered devices some time to settle */
        msleep(100);
    }

    parport_adapter.dev.parent = &pdev->dev;
    err = i2c_bit_add_bus(&parport_adapter);
    if (err) {
        dev_err(&pdev->dev, "Unable to register with I2C\n");
        return err;
    }

    /* Setup SMBus alert if supported */
    if (adapter_parm[type].smbus_alert && irq) {
        alert_data.irq = irq;
        ara = i2c_setup_smbus_alert(&parport_adapter, &alert_data);
        if (ara)
            line_set(1, &parport_ctrl_irq);
        else
            dev_warn(&pdev->dev, "Failed to register ARA client\n");
    }

    return 0;
}

static int __devexit i2c_parport_remove(struct platform_device *pdev)
{
    if (ara) {
        line_set(0, &parport_ctrl_irq);
        i2c_unregister_device(ara);
        ara = NULL;
    }
    i2c_del_adapter(&parport_adapter);

    /* Un-init if needed (power off...) */
    if (adapter_parm[type].init.val)
        line_set(0, &adapter_parm[type].init);

    return 0;
}

static struct platform_driver i2c_parport_driver = {
    .driver = {
        .owner  = THIS_MODULE,
        .name   = DRVNAME,
    },
    .probe      = i2c_parport_probe,
    .remove     = __devexit_p(i2c_parport_remove),
};

static int __init i2c_parport_device_add(u16 address)
{
    int err;

    pdev = platform_device_alloc(DRVNAME, -1);
    if (!pdev) {
        err = -ENOMEM;
        printk(KERN_ERR DRVNAME ": Device allocation failed\n");
        goto exit;
    }

    err = platform_device_add(pdev);
    if (err) {
        printk(KERN_ERR DRVNAME ": Device addition failed (%d)\n",
               err);
        goto exit_device_put;
    }

    return 0;

exit_device_put:
    platform_device_put(pdev);
exit:
    return err;
}

static int __init i2c_parport_init(void)
{
    int err;

    if (type < 0) {
        printk(KERN_ERR DRVNAME ": adapter type unspecified\n");
        return -ENODEV;
    }

    if (type >= ARRAY_SIZE(adapter_parm)) {
        printk(KERN_ERR DRVNAME ": invalid type (%d)\n", type);
        return -ENODEV;
    }

    if (base == 0) {
        pr_info(DRVNAME ": using default base 0x%x\n", DEFAULT_BASE);
        base = DEFAULT_BASE;
    }

    if (!request_region(base, 3, DRVNAME))
        return -EBUSY;

    if (irq != 0)
        pr_info(DRVNAME ": using irq %d\n", irq);

    if (!adapter_parm[type].getscl.val)
        parport_algo_data.getscl = NULL;

    /* Sets global pdev as a side effect */
    err = i2c_parport_device_add(base);
    if (err)
        goto exit_release;

    err = platform_driver_register(&i2c_parport_driver);
    if (err)
        goto exit_device;

    return 0;

exit_device:
    platform_device_unregister(pdev);
exit_release:
    release_region(base, 3);
    return err;
}

static void __exit i2c_parport_exit(void)
{
    platform_driver_unregister(&i2c_parport_driver);
    platform_device_unregister(pdev);
    release_region(base, 3);
}

MODULE_AUTHOR("Jean Delvare <[email protected]>");
MODULE_DESCRIPTION("I2C bus over parallel port (light)");
MODULE_LICENSE("GPL");

module_init(i2c_parport_init);
module_exit(i2c_parport_exit);