diff --git a/hw/i2c/smbus.c b/hw/i2c/smbus.c
index a8931b7..18fb4d1 100644
--- a/hw/i2c/smbus.c
+++ b/hw/i2c/smbus.c
@@ -208,34 +208,44 @@ static int smbus_device_init(I2CSlave *i2c)
 }
 
 /* Master device commands.  */
-void smbus_quick_command(i2c_bus *bus, uint8_t addr, int read)
+int smbus_quick_command(i2c_bus *bus, uint8_t addr, int read)
 {
-    i2c_start_transfer(bus, addr, read);
+    if (i2c_start_transfer(bus, addr, read)) {
+        return -1;
+    }
     i2c_end_transfer(bus);
+    return 0;
 }
 
 int smbus_receive_byte(i2c_bus *bus, uint8_t addr)
 {
     uint8_t data;
 
-    i2c_start_transfer(bus, addr, 1);
+    if (i2c_start_transfer(bus, addr, 1)) {
+        return -1;
+    }
     data = i2c_recv(bus);
     i2c_nack(bus);
     i2c_end_transfer(bus);
     return data;
 }
 
-void smbus_send_byte(i2c_bus *bus, uint8_t addr, uint8_t data)
+int smbus_send_byte(i2c_bus *bus, uint8_t addr, uint8_t data)
 {
-    i2c_start_transfer(bus, addr, 0);
+    if (i2c_start_transfer(bus, addr, 0)) {
+        return -1;
+    }
     i2c_send(bus, data);
     i2c_end_transfer(bus);
+    return 0;
 }
 
 int smbus_read_byte(i2c_bus *bus, uint8_t addr, uint8_t command)
 {
     uint8_t data;
-    i2c_start_transfer(bus, addr, 0);
+    if (i2c_start_transfer(bus, addr, 0)) {
+        return -1;
+    }
     i2c_send(bus, command);
     i2c_start_transfer(bus, addr, 1);
     data = i2c_recv(bus);
@@ -244,18 +254,23 @@ int smbus_read_byte(i2c_bus *bus, uint8_t addr, uint8_t command)
     return data;
 }
 
-void smbus_write_byte(i2c_bus *bus, uint8_t addr, uint8_t command, uint8_t data)
+int smbus_write_byte(i2c_bus *bus, uint8_t addr, uint8_t command, uint8_t data)
 {
-    i2c_start_transfer(bus, addr, 0);
+    if (i2c_start_transfer(bus, addr, 0)) {
+        return -1;
+    }
     i2c_send(bus, command);
     i2c_send(bus, data);
     i2c_end_transfer(bus);
+    return 0;
 }
 
 int smbus_read_word(i2c_bus *bus, uint8_t addr, uint8_t command)
 {
     uint16_t data;
-    i2c_start_transfer(bus, addr, 0);
+    if (i2c_start_transfer(bus, addr, 0)) {
+        return -1;
+    }
     i2c_send(bus, command);
     i2c_start_transfer(bus, addr, 1);
     data = i2c_recv(bus);
@@ -265,13 +280,16 @@ int smbus_read_word(i2c_bus *bus, uint8_t addr, uint8_t command)
     return data;
 }
 
-void smbus_write_word(i2c_bus *bus, uint8_t addr, uint8_t command, uint16_t data)
+int smbus_write_word(i2c_bus *bus, uint8_t addr, uint8_t command, uint16_t data)
 {
-    i2c_start_transfer(bus, addr, 0);
+    if (i2c_start_transfer(bus, addr, 0)) {
+        return -1;
+    }
     i2c_send(bus, command);
     i2c_send(bus, data & 0xff);
     i2c_send(bus, data >> 8);
     i2c_end_transfer(bus);
+    return 0;
 }
 
 int smbus_read_block(i2c_bus *bus, uint8_t addr, uint8_t command, uint8_t *data)
@@ -279,33 +297,41 @@ int smbus_read_block(i2c_bus *bus, uint8_t addr, uint8_t command, uint8_t *data)
     int len;
     int i;
 
-    i2c_start_transfer(bus, addr, 0);
+    if (i2c_start_transfer(bus, addr, 0)) {
+        return -1;
+    }
     i2c_send(bus, command);
     i2c_start_transfer(bus, addr, 1);
     len = i2c_recv(bus);
-    if (len > 32)
+    if (len > 32) {
         len = 0;
-    for (i = 0; i < len; i++)
+    }
+    for (i = 0; i < len; i++) {
         data[i] = i2c_recv(bus);
+    }
     i2c_nack(bus);
     i2c_end_transfer(bus);
     return len;
 }
 
-void smbus_write_block(i2c_bus *bus, uint8_t addr, uint8_t command, uint8_t *data,
-                       int len)
+int smbus_write_block(i2c_bus *bus, uint8_t addr, uint8_t command, uint8_t *data,
+                      int len)
 {
     int i;
 
     if (len > 32)
         len = 32;
 
-    i2c_start_transfer(bus, addr, 0);
+    if (i2c_start_transfer(bus, addr, 0)) {
+        return -1;
+    }
     i2c_send(bus, command);
     i2c_send(bus, len);
-    for (i = 0; i < len; i++)
+    for (i = 0; i < len; i++) {
         i2c_send(bus, data[i]);
+    }
     i2c_end_transfer(bus);
+    return 0;
 }
 
 static void smbus_device_class_init(ObjectClass *klass, void *data)
diff --git a/include/hw/i2c/smbus.h b/include/hw/i2c/smbus.h
index 4293733..358f35c 100644
--- a/include/hw/i2c/smbus.h
+++ b/include/hw/i2c/smbus.h
@@ -66,16 +66,16 @@ struct SMBusDevice {
 };
 
 /* Master device commands.  */
-void smbus_quick_command(i2c_bus *bus, uint8_t addr, int read);
+int smbus_quick_command(i2c_bus *bus, uint8_t addr, int read);
 int smbus_receive_byte(i2c_bus *bus, uint8_t addr);
-void smbus_send_byte(i2c_bus *bus, uint8_t addr, uint8_t data);
+int smbus_send_byte(i2c_bus *bus, uint8_t addr, uint8_t data);
 int smbus_read_byte(i2c_bus *bus, uint8_t addr, uint8_t command);
-void smbus_write_byte(i2c_bus *bus, uint8_t addr, uint8_t command, uint8_t data);
+int smbus_write_byte(i2c_bus *bus, uint8_t addr, uint8_t command, uint8_t data);
 int smbus_read_word(i2c_bus *bus, uint8_t addr, uint8_t command);
-void smbus_write_word(i2c_bus *bus, uint8_t addr, uint8_t command, uint16_t data);
+int smbus_write_word(i2c_bus *bus, uint8_t addr, uint8_t command, uint16_t data);
 int smbus_read_block(i2c_bus *bus, uint8_t addr, uint8_t command, uint8_t *data);
-void smbus_write_block(i2c_bus *bus, uint8_t addr, uint8_t command, uint8_t *data,
-                       int len);
+int smbus_write_block(i2c_bus *bus, uint8_t addr, uint8_t command, uint8_t *data,
+                      int len);
 
 void smbus_eeprom_init(i2c_bus *smbus, int nb_eeprom,
                        const uint8_t *eeprom_spd, int size);
