hw/i2c.c

   1 /*
   2  * QEMU I2C bus interface.
   3  *
   4  * Copyright (c) 2007 CodeSourcery.
   5  * Written by Paul Brook
   6  *
   7  * This code is licenced under the LGPL.
   8  */
   9
  10 #include "hw.h"
  11 #include "i2c.h"
  12
  13 struct i2c_bus
  14 {
  15     i2c_slave *current_dev;
  16     i2c_slave *dev;
  17     int saved_address;
  18 };
  19
  20 static void i2c_bus_save(QEMUFile *f, void *opaque)
  21 {
  22     i2c_bus *bus = (i2c_bus *)opaque;
  23
  24     qemu_put_byte(f, bus->current_dev ? bus->current_dev->address : -1);
  25 }
  26
  27 static int i2c_bus_load(QEMUFile *f, void *opaque, int version_id)
  28 {
  29     i2c_bus *bus = (i2c_bus *)opaque;
  30
  31     if (version_id != 1)
  32         return -EINVAL;
  33
  34     /* The bus is loaded before attached devices, so load and save the
  35        current device id.  Devices will check themselves as loaded.  */
  36     bus->saved_address = (int8_t) qemu_get_byte(f);
  37     bus->current_dev = NULL;
  38
  39     return 0;
  40 }
  41
  42 /* Create a new I2C bus.  */
  43 i2c_bus *i2c_init_bus(void)
  44 {
  45     i2c_bus *bus;
  46
  47     bus = (i2c_bus *)qemu_mallocz(sizeof(i2c_bus));
  48     register_savevm("i2c_bus", -1, 1, i2c_bus_save, i2c_bus_load, bus);
  49     return bus;
  50 }
  51
  52 /* Create a new slave device.  */
  53 i2c_slave *i2c_slave_init(i2c_bus *bus, int address, int size)
  54 {
  55     i2c_slave *dev;
  56
  57     if (size < sizeof(i2c_slave))
  58         hw_error("I2C struct too small");
  59
  60     dev = (i2c_slave *)qemu_mallocz(size);
  61     dev->address = address;
  62     dev->next = bus->dev;
  63     bus->dev = dev;
  64     dev->bus = bus;
  65
  66     return dev;
  67 }
  68
  69 void i2c_set_slave_address(i2c_slave *dev, int address)
  70 {
  71     dev->address = address;
  72 }
  73
  74 /* Return nonzero if bus is busy.  */
  75 int i2c_bus_busy(i2c_bus *bus)
  76 {
  77     return bus->current_dev != NULL;
  78 }
  79
  80 /* Returns non-zero if the address is not valid.  */
  81 /* TODO: Make this handle multiple masters.  */
  82 int i2c_start_transfer(i2c_bus *bus, int address, int recv)
  83 {
  84     i2c_slave *dev;
  85
  86     for (dev = bus->dev; dev; dev = dev->next) {
  87         if (dev->address == address)
  88             break;
  89     }
  90
  91     if (!dev)
  92         return 1;
  93
  94     /* If the bus is already busy, assume this is a repeated
  95        start condition.  */
  96     bus->current_dev = dev;
  97     dev->event(dev, recv ? I2C_START_RECV : I2C_START_SEND);
  98     return 0;
  99 }
 100
 101 void i2c_end_transfer(i2c_bus *bus)
 102 {
 103     i2c_slave *dev = bus->current_dev;
 104
 105     if (!dev)
 106         return;
 107
 108     dev->event(dev, I2C_FINISH);
 109
 110     bus->current_dev = NULL;
 111 }
 112
 113 int i2c_send(i2c_bus *bus, uint8_t data)
 114 {
 115     i2c_slave *dev = bus->current_dev;
 116
 117     if (!dev)
 118         return -1;
 119
 120     return dev->send(dev, data);
 121 }
 122
 123 int i2c_recv(i2c_bus *bus)
 124 {
 125     i2c_slave *dev = bus->current_dev;
 126
 127     if (!dev)
 128         return -1;
 129
 130     return dev->recv(dev);
 131 }
 132
 133 void i2c_nack(i2c_bus *bus)
 134 {
 135     i2c_slave *dev = bus->current_dev;
 136
 137     if (!dev)
 138         return;
 139
 140     dev->event(dev, I2C_NACK);
 141 }
 142
 143 void i2c_slave_save(QEMUFile *f, i2c_slave *dev)
 144 {
 145     qemu_put_byte(f, dev->address);
 146 }
 147
 148 void i2c_slave_load(QEMUFile *f, i2c_slave *dev)
 149 {
 150     dev->address = qemu_get_byte(f);
 151     if (dev->bus->saved_address == dev->address)
 152         dev->bus->current_dev = dev;
 153 }