drivers/char/i2c-parport.c

   1 /*
   2  * I2C driver for parallel port
   3  *
   4  * Author: Phil Blundell <philb@gnu.org>
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public License
   8  * as published by the Free Software Foundation; either version
   9  * 2 of the License, or (at your option) any later version.
  10  *
  11  * This driver implements a simple I2C protocol by bit-twiddling some
  12  * signals on the parallel port.  Since the outputs on the parallel port
  13  * aren't open collector, three lines rather than two are used:
  14  *
  15  *      D0      clock out
  16  *      D1      data out
  17  *      BUSY    data in
  18  */
  19
  20 #include <linux/parport.h>
  21 #include <linux/module.h>
  22 #include <linux/delay.h>
  23 #include <linux/i2c.h>
  24 #include <linux/init.h>
  25 #include <asm/spinlock.h>
  26
  27 #define I2C_DELAY   10
  28
  29 static int debug = 0;
  30
  31 struct parport_i2c_bus
  32 {
  33   struct i2c_bus i2c;
  34   struct parport_i2c_bus *next;
  35 };
  36
  37 static struct parport_i2c_bus *bus_list;
  38
  39 #ifdef __SMP__
  40 static spinlock_t bus_list_lock = SPIN_LOCK_UNLOCKED;
  41 #endif
  42
  43 /* software I2C functions */
  44
  45 static void i2c_setlines(struct i2c_bus *bus, int clk, int data)
  46 {
  47   struct parport *p = bus->data;
  48   parport_write_data(p, (clk?1:0) | (data?2:0));
  49   udelay(I2C_DELAY);
  50 }
  51
  52 static int i2c_getdataline(struct i2c_bus *bus)
  53 {
  54   struct parport *p = bus->data;
  55   return (parport_read_status(p) & PARPORT_STATUS_BUSY) ? 0 : 1;
  56 }
  57
  58 static struct i2c_bus parport_i2c_bus_template =
  59 {
  60   "...",
  61   I2C_BUSID_PARPORT,
  62   NULL,
  63
  64   SPIN_LOCK_UNLOCKED,
  65
  66   NULL,
  67   NULL,
  68
  69   i2c_setlines,
  70   i2c_getdataline,
  71   NULL,
  72   NULL,
  73 };
  74
  75 static void i2c_parport_attach(struct parport *port)
  76 {
  77   struct parport_i2c_bus *b = kmalloc(sizeof(struct parport_i2c_bus),
  78                                       GFP_KERNEL);
  79   b->i2c = parport_i2c_bus_template;
  80   b->i2c.data = port;
  81   strncpy(b->i2c.name, port->name, 32);
  82   spin_lock(&bus_list_lock);
  83   b->next = bus_list;
  84   bus_list = b;
  85   spin_unlock(&bus_list_lock);
  86   i2c_register_bus(&b->i2c);
  87   if (debug)
  88     printk(KERN_DEBUG "i2c: attached to %s\n", port->name);
  89 }
  90
  91 static void i2c_parport_detach(struct parport *port)
  92 {
  93   struct parport_i2c_bus *b, *old_b = NULL;
  94   spin_lock(&bus_list_lock);
  95   b = bus_list;
  96   while (b)
  97   {
  98     if (b->i2c.data == port)
  99     {
 100       if (old_b)
 101         old_b->next = b->next;
 102       else
 103         bus_list = b->next;
 104       i2c_unregister_bus(&b->i2c);
 105       kfree(b);
 106       break;
 107     }
 108     old_b = b;
 109     b = b->next;
 110   }
 111   spin_unlock(&bus_list_lock);
 112   if (debug)
 113     printk(KERN_DEBUG "i2c: detached from %s\n", port->name);
 114 }
 115
 116 static struct parport_driver parport_i2c_driver =
 117 {
 118   "i2c",
 119   i2c_parport_attach,
 120   i2c_parport_detach
 121 };
 122
 123 #ifdef MODULE
 124 int init_module(void)
 125 #else
 126 int __init i2c_parport_init(void)
 127 #endif
 128 {
 129   printk("I2C: driver for parallel port v0.1 philb@gnu.org\n");
 130   parport_register_driver(&parport_i2c_driver);
 131   return 0;
 132 }
 133
 134 #ifdef MODULE
 135 MODULE_PARM(debug, "i");
 136
 137 void cleanup_module(void)
 138 {
 139   struct parport_i2c_bus *b = bus_list;
 140   while (b)
 141   {
 142     struct parport_i2c_bus *next = b->next;
 143     i2c_unregister_bus(&b->i2c);
 144     kfree(b);
 145     b = next;
 146   }
 147   parport_unregister_driver(&parport_i2c_driver);
 148 }
 149 #endif