hw/misc/i2c-echo: add tracing

This has been useful when debugging and unsure if the guest is
generating i2c traffic.

Signed-off-by: Titus Rwantare <titusr@google.com>
Reviewed-by: Hao Wu <wuhaotsh@google.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20250121105935.3069035-1-titusr@google.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>

hw/misc/i2c-echo.c

@@ -13,6 +13,7 @@
 #include "qemu/main-loop.h"
 #include "block/aio.h"
 #include "hw/i2c/i2c.h"
+#include "trace.h"
 
 #define TYPE_I2C_ECHO "i2c-echo"
 OBJECT_DECLARE_SIMPLE_TYPE(I2CEchoState, I2C_ECHO)
@@ -80,11 +81,13 @@ static int i2c_echo_event(I2CSlave *s, enum i2c_event event)
     case I2C_START_RECV:
         state->pos = 0;
 
+        trace_i2c_echo_event(DEVICE(s)->canonical_path, "I2C_START_RECV");
         break;
 
     case I2C_START_SEND:
         state->pos = 0;
 
+        trace_i2c_echo_event(DEVICE(s)->canonical_path, "I2C_START_SEND");
         break;
 
     case I2C_FINISH:
@@ -92,12 +95,15 @@ static int i2c_echo_event(I2CSlave *s, enum i2c_event event)
         state->state = I2C_ECHO_STATE_START_SEND;
         i2c_bus_master(state->bus, state->bh);
 
+        trace_i2c_echo_event(DEVICE(s)->canonical_path, "I2C_FINISH");
         break;
 
     case I2C_NACK:
+        trace_i2c_echo_event(DEVICE(s)->canonical_path, "I2C_NACK");
         break;
 
     default:
+        trace_i2c_echo_event(DEVICE(s)->canonical_path, "UNHANDLED");
         return -1;
     }
 
@@ -112,6 +118,7 @@ static uint8_t i2c_echo_recv(I2CSlave *s)
         return 0xff;
     }
 
+    trace_i2c_echo_recv(DEVICE(s)->canonical_path, state->data[state->pos]);
     return state->data[state->pos++];
 }
 
@@ -119,6 +126,7 @@ static int i2c_echo_send(I2CSlave *s, uint8_t data)
 {
     I2CEchoState *state = I2C_ECHO(s);
 
+    trace_i2c_echo_send(DEVICE(s)->canonical_path, data);
     if (state->pos > 2) {
         return -1;
     }

hw/misc/trace-events

@@ -390,3 +390,8 @@ ivshmem_flat_read_write_mmr_invalid(uint64_t addr_offset) "No ivshmem register m
 ivshmem_flat_interrupt_invalid_peer(uint16_t peer_id) "Can't interrupt non-existing peer %u"
 ivshmem_flat_write_mmr(uint64_t addr_offset) "Write access at offset %"PRIu64
 ivshmem_flat_interrupt_peer(uint16_t peer_id, uint16_t vector_id) "Interrupting peer ID %u, vector %u..."
+
+# i2c-echo.c
+i2c_echo_event(const char *id, const char *event) "%s: %s"
+i2c_echo_recv(const char *id, uint8_t data) "%s: recv 0x%02" PRIx8
+i2c_echo_send(const char *id, uint8_t data) "%s: send 0x%02" PRIx8