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i2c-parport-light.c

/* ------------------------------------------------------------------------ *
 * i2c-parport-light.c I2C bus over parallel port                           *
 * ------------------------------------------------------------------------ *
   Copyright (C) 2003-2007 Jean Delvare <khali@linux-fr.org>
   
   Based on older i2c-velleman.c driver
   Copyright (C) 1995-2000 Simon G. Vogl
   With some changes from:
   Frodo Looijaard <frodol@dds.nl>
   Kyösti Mälkki <kmalkki@cc.hut.fi>
   
   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/platform_device.h>
#include <linux/ioport.h>
#include <linux/i2c.h>
#include <linux/i2c-algo-bit.h>
#include <asm/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");

/* ----- 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,
      .id         = I2C_HW_B_LP,
      .algo_data  = &parport_algo_data,
      .name       = "Parallel port adapter (light)",
};

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

      res = platform_get_resource(pdev, IORESOURCE_IO, 0);
      if (!request_region(res->start, res->end - res->start + 1, DRVNAME))
            return -EBUSY;

      /* 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);

      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");
            goto exit_region;
      }
      return 0;

exit_region:
      release_region(res->start, res->end - res->start + 1);
      return err;
}

static int __devexit i2c_parport_remove(struct platform_device *pdev)
{
      struct resource *res;

      i2c_del_adapter(&parport_adapter);

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

      res = platform_get_resource(pdev, IORESOURCE_IO, 0);
      release_region(res->start, res->end - res->start + 1);
      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)
{
      struct resource res = {
            .start      = address,
            .end  = address + 2,
            .name = DRVNAME,
            .flags      = IORESOURCE_IO,
      };
      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_resources(pdev, &res, 1);
      if (err) {
            printk(KERN_ERR DRVNAME ": Device resource addition failed "
                   "(%d)\n", err);
            goto exit_device_put;
      }

      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 (!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;

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

      return 0;

exit_device:
      platform_device_unregister(pdev);
exit:
      return err;
}

static void __exit i2c_parport_exit(void)
{
      platform_driver_unregister(&i2c_parport_driver);
      platform_device_unregister(pdev);
}

MODULE_AUTHOR("Jean Delvare <khali@linux-fr.org>");
MODULE_DESCRIPTION("I2C bus over parallel port (light)");
MODULE_LICENSE("GPL");

module_init(i2c_parport_init);
module_exit(i2c_parport_exit);

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