hw/misc/i2c-echo.c

   1 /*
   2  * Example I2C device using asynchronous I2C send.
   3  *
   4  * Copyright (C) 2023 Samsung Electronics Co., Ltd. All Rights Reserved.
   5  *
   6  * This work is licensed under the terms of the GNU GPL, version 2.  See
   7  * the COPYING file in the top-level directory.
   8  *
   9  */
  10
  11 #include "qemu/osdep.h"
  12 #include "qemu/timer.h"
  13 #include "qemu/main-loop.h"
  14 #include "block/aio.h"
  15 #include "hw/i2c/i2c.h"
  16
  17 #define TYPE_I2C_ECHO "i2c-echo"
  18 OBJECT_DECLARE_SIMPLE_TYPE(I2CEchoState, I2C_ECHO)
  19
  20 enum i2c_echo_state {
  21     I2C_ECHO_STATE_IDLE,
  22     I2C_ECHO_STATE_START_SEND,
  23     I2C_ECHO_STATE_ACK,
  24 };
  25
  26 typedef struct I2CEchoState {
  27     I2CSlave parent_obj;
  28
  29     I2CBus *bus;
  30
  31     enum i2c_echo_state state;
  32     QEMUBH *bh;
  33
  34     unsigned int pos;
  35     uint8_t data[3];
  36 } I2CEchoState;
  37
  38 static void i2c_echo_bh(void *opaque)
  39 {
  40     I2CEchoState *state = opaque;
  41
  42     switch (state->state) {
  43     case I2C_ECHO_STATE_IDLE:
  44         return;
  45
  46     case I2C_ECHO_STATE_START_SEND:
  47         if (i2c_start_send_async(state->bus, state->data[0])) {
  48             goto release_bus;
  49         }
  50
  51         state->pos++;
  52         state->state = I2C_ECHO_STATE_ACK;
  53         return;
  54
  55     case I2C_ECHO_STATE_ACK:
  56         if (state->pos > 2) {
  57             break;
  58         }
  59
  60         if (i2c_send_async(state->bus, state->data[state->pos++])) {
  61             break;
  62         }
  63
  64         return;
  65     }
  66
  67
  68     i2c_end_transfer(state->bus);
  69 release_bus:
  70     i2c_bus_release(state->bus);
  71
  72     state->state = I2C_ECHO_STATE_IDLE;
  73 }
  74
  75 static int i2c_echo_event(I2CSlave *s, enum i2c_event event)
  76 {
  77     I2CEchoState *state = I2C_ECHO(s);
  78
  79     switch (event) {
  80     case I2C_START_RECV:
  81         state->pos = 0;
  82
  83         break;
  84
  85     case I2C_START_SEND:
  86         state->pos = 0;
  87
  88         break;
  89
  90     case I2C_FINISH:
  91         state->pos = 0;
  92         state->state = I2C_ECHO_STATE_START_SEND;
  93         i2c_bus_master(state->bus, state->bh);
  94
  95         break;
  96
  97     case I2C_NACK:
  98         break;
  99
 100     default:
 101         return -1;
 102     }
 103
 104     return 0;
 105 }
 106
 107 static uint8_t i2c_echo_recv(I2CSlave *s)
 108 {
 109     I2CEchoState *state = I2C_ECHO(s);
 110
 111     if (state->pos > 2) {
 112         return 0xff;
 113     }
 114
 115     return state->data[state->pos++];
 116 }
 117
 118 static int i2c_echo_send(I2CSlave *s, uint8_t data)
 119 {
 120     I2CEchoState *state = I2C_ECHO(s);
 121
 122     if (state->pos > 2) {
 123         return -1;
 124     }
 125
 126     state->data[state->pos++] = data;
 127
 128     return 0;
 129 }
 130
 131 static void i2c_echo_realize(DeviceState *dev, Error **errp)
 132 {
 133     I2CEchoState *state = I2C_ECHO(dev);
 134     BusState *bus = qdev_get_parent_bus(dev);
 135
 136     state->bus = I2C_BUS(bus);
 137     state->bh = qemu_bh_new(i2c_echo_bh, state);
 138
 139     return;
 140 }
 141
 142 static void i2c_echo_class_init(ObjectClass *oc, void *data)
 143 {
 144     I2CSlaveClass *sc = I2C_SLAVE_CLASS(oc);
 145     DeviceClass *dc = DEVICE_CLASS(oc);
 146
 147     dc->realize = i2c_echo_realize;
 148
 149     sc->event = i2c_echo_event;
 150     sc->recv = i2c_echo_recv;
 151     sc->send = i2c_echo_send;
 152 }
 153
 154 static const TypeInfo i2c_echo = {
 155     .name = TYPE_I2C_ECHO,
 156     .parent = TYPE_I2C_SLAVE,
 157     .instance_size = sizeof(I2CEchoState),
 158     .class_init = i2c_echo_class_init,
 159 };
 160
 161 static void register_types(void)
 162 {
 163     type_register_static(&i2c_echo);
 164 }
 165
 166 type_init(register_types);