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 <linux/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 static spinlock_t bus_list_lock = SPIN_LOCK_UNLOCKED;
  40
  41 /* software I2C functions */
  42
  43 static void i2c_setlines(struct i2c_bus *bus, int clk, int data)
  44 {
  45   struct parport *p = bus->data;
  46   parport_write_data(p, (clk?1:0) | (data?2:0));
  47   udelay(I2C_DELAY);
  48 }
  49
  50 static int i2c_getdataline(struct i2c_bus *bus)
  51 {
  52   struct parport *p = bus->data;
  53   return (parport_read_status(p) & PARPORT_STATUS_BUSY) ? 0 : 1;
  54 }
  55
  56 static struct i2c_bus parport_i2c_bus_template =
  57 {
  58   "...",
  59   I2C_BUSID_PARPORT,
  60   NULL,
  61
  62   SPIN_LOCK_UNLOCKED,
  63
  64   NULL,
  65   NULL,
  66
  67   i2c_setlines,
  68   i2c_getdataline,
  69   NULL,
  70   NULL,
  71 };
  72
  73 static void i2c_parport_attach(struct parport *port)
  74 {
  75   struct parport_i2c_bus *b = kmalloc(sizeof(struct parport_i2c_bus),
  76                                       GFP_KERNEL);
  77   b->i2c = parport_i2c_bus_template;
  78   b->i2c.data = port;
  79   strncpy(b->i2c.name, port->name, 32);
  80   spin_lock(&bus_list_lock);
  81   b->next = bus_list;
  82   bus_list = b;
  83   spin_unlock(&bus_list_lock);
  84   i2c_register_bus(&b->i2c);
  85   if (debug)
  86     printk(KERN_DEBUG "i2c: attached to %s\n", port->name);
  87 }
  88
  89 static void i2c_parport_detach(struct parport *port)
  90 {
  91   struct parport_i2c_bus *b, *old_b = NULL;
  92   spin_lock(&bus_list_lock);
  93   b = bus_list;
  94   while (b)
  95   {
  96     if (b->i2c.data == port)
  97     {
  98       if (old_b)
  99         old_b->next = b->next;
 100       else
 101         bus_list = b->next;
 102       i2c_unregister_bus(&b->i2c);
 103       kfree(b);
 104       break;
 105     }
 106     old_b = b;
 107     b = b->next;
 108   }
 109   spin_unlock(&bus_list_lock);
 110   if (debug)
 111     printk(KERN_DEBUG "i2c: detached from %s\n", port->name);
 112 }
 113
 114 static struct parport_driver parport_i2c_driver =
 115 {
 116   "i2c",
 117   i2c_parport_attach,
 118   i2c_parport_detach
 119 };
 120
 121 #ifdef MODULE
 122 int init_module(void)
 123 #else
 124 int __init i2c_parport_init(void)
 125 #endif
 126 {
 127   printk("I2C: driver for parallel port v0.1 philb@gnu.org\n");
 128   parport_register_driver(&parport_i2c_driver);
 129   return 0;
 130 }
 131
 132 #ifdef MODULE
 133 MODULE_PARM(debug, "i");
 134
 135 void cleanup_module(void)
 136 {
 137   struct parport_i2c_bus *b = bus_list;
 138   while (b)
 139   {
 140     struct parport_i2c_bus *next = b->next;
 141     i2c_unregister_bus(&b->i2c);
 142     kfree(b);
 143     b = next;
 144   }
 145   parport_unregister_driver(&parport_i2c_driver);
 146 }
 147 #endif