[RFC,4/4] hw/misc: add a toy i2c echo device

Commit Message

Klaus Jensen March 31, 2022, 4:57 p.m. UTC

From: Klaus Jensen <[e-mail]>

Add an example i2c device that can master the bus. The device will echo
whatever it is sent to the device identified by the first byte received.

Signed-off-by: Klaus Jensen <[e-mail]>
---
 hw/misc/i2c-echo.c | 144 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 144 insertions(+)
 create mode 100644 hw/misc/i2c-echo.c

Patch

diff --git a/hw/misc/i2c-echo.c b/hw/misc/i2c-echo.c
new file mode 100644
index 000000000000..72155d850d5f
--- /dev/null
+++ b/hw/misc/i2c-echo.c
@@ -0,0 +1,144 @@ 
+#include "qemu/osdep.h"
+#include "qemu/timer.h"
+#include "qemu/main-loop.h"
+#include "block/aio.h"
+#include "hw/i2c/i2c.h"
+
+#define TYPE_I2C_ECHO "i2c-echo"
+OBJECT_DECLARE_SIMPLE_TYPE(I2CEchoState, I2C_ECHO)
+
+enum i2c_echo_state {
+    I2C_ECHO_STATE_REQUEST_MASTER,
+    I2C_ECHO_STATE_START_SEND,
+    I2C_ECHO_STATE_ACK,
+};
+
+typedef struct I2CEchoState {
+    I2CSlave parent_obj;
+
+    I2CBus *bus;
+
+    enum i2c_echo_state state;
+    QEMUBH *bh;
+
+    unsigned int pos;
+    uint8_t data[3];
+} I2CEchoState;
+
+static void i2c_echo_bh(void *opaque)
+{
+    I2CEchoState *state = opaque;
+
+    switch (state->state) {
+    case I2C_ECHO_STATE_REQUEST_MASTER:
+        i2c_bus_master(state->bus, state->bh);
+        state->state = I2C_ECHO_STATE_START_SEND;
+        break;
+
+    case I2C_ECHO_STATE_START_SEND:
+        i2c_start_send(state->bus, state->data[0]);
+        state->pos++;
+        state->state = I2C_ECHO_STATE_ACK;
+        break;
+
+    case I2C_ECHO_STATE_ACK:
+        if (state->pos > 2) {
+            i2c_end_transfer(state->bus);
+            i2c_bus_release(state->bus);
+            break;
+        }
+
+        i2c_send_async(state->bus, state->data[state->pos++]);
+        break;
+    }
+}
+
+static int i2c_echo_event(I2CSlave *s, enum i2c_event event)
+{
+    I2CEchoState *state = I2C_ECHO(s);
+
+    switch (event) {
+    case I2C_START_RECV:
+        state->pos = 0;
+
+        break;
+
+    case I2C_START_SEND:
+        state->pos = 0;
+
+        break;
+
+    case I2C_FINISH:
+        state->pos = 0;
+        state->state = I2C_ECHO_STATE_REQUEST_MASTER;
+        qemu_bh_schedule(state->bh);
+
+        break;
+
+    case I2C_NACK:
+        break;
+    }
+
+    return 0;
+}
+
+static uint8_t i2c_echo_recv(I2CSlave *s)
+{
+    I2CEchoState *state = I2C_ECHO(s);
+
+    if (state->pos > 2) {
+        return 0xff;
+    }
+
+    return state->data[state->pos++];
+}
+
+static int i2c_echo_send(I2CSlave *s, uint8_t data)
+{
+    I2CEchoState *state = I2C_ECHO(s);
+
+    if (state->pos > 2) {
+        return -1;
+    }
+
+    state->data[state->pos++] = data;
+
+    return 0;
+}
+
+static void i2c_echo_realize(DeviceState *dev, Error **errp)
+{
+    I2CEchoState *state = I2C_ECHO(dev);
+    BusState *bus = qdev_get_parent_bus(dev);
+
+    state->bus = I2C_BUS(bus);
+    state->bh = qemu_bh_new(i2c_echo_bh, state);
+
+    return;
+}
+
+static void i2c_echo_class_init(ObjectClass *oc, void *data)
+{
+    I2CSlaveClass *sc = I2C_SLAVE_CLASS(oc);
+    DeviceClass *dc = DEVICE_CLASS(oc);
+
+    dc->realize = i2c_echo_realize;
+
+    sc->event = i2c_echo_event;
+    sc->recv = i2c_echo_recv;
+    sc->send = i2c_echo_send;
+}
+
+static const TypeInfo i2c_echo = {
+    .name = TYPE_I2C_ECHO,
+    .parent = TYPE_I2C_SLAVE,
+    .instance_size = sizeof(I2CEchoState),
+    .class_init = i2c_echo_class_init,
+};
+
+static void register_types(void)
+{
+    type_register_static(&i2c_echo);
+}
+
+type_init(register_types);