STM I2C: manage Is Device Ready case

Some device drivers use a data lenght of 0 to check if device is ready.
STM32 HAL provides a dedicated service for that, so let's use it.

Author: LMESTM

targets/TARGET_STM/i2c_api.c

@@ -634,9 +634,16 @@ void i2c_reset(i2c_t *obj) {
 int i2c_read(i2c_t *obj, int address, char *data, int length, int stop) {
     struct i2c_s *obj_s = I2C_S(obj);
     I2C_HandleTypeDef *handle = &(obj_s->handle);
-    int count = 0, ret = 0;
+    int count = I2C_ERROR_BUS_BUSY, ret = 0;
     uint32_t timeout = 0;
 
+    if((length == 0) || (data == 0)) {
+        if(HAL_I2C_IsDeviceReady(handle, address, 1, 10) == HAL_OK)
+            return 0;
+        else
+            return I2C_ERROR_BUS_BUSY;
+    }
+
     if ((obj_s->XferOperation == I2C_FIRST_AND_LAST_FRAME) ||
         (obj_s->XferOperation == I2C_LAST_FRAME)) {
         if (stop)
@@ -686,9 +693,16 @@ int i2c_read(i2c_t *obj, int address, char *data, int length, int stop) {
 int i2c_write(i2c_t *obj, int address, const char *data, int length, int stop) {
     struct i2c_s *obj_s = I2C_S(obj);
     I2C_HandleTypeDef *handle = &(obj_s->handle);
-    int count = 0, ret = 0;
+    int count = I2C_ERROR_BUS_BUSY, ret = 0;
     uint32_t timeout = 0;
 
+    if((length == 0) || (data == 0)) {
+        if(HAL_I2C_IsDeviceReady(handle, address, 1, 10) == HAL_OK)
+            return 0;
+        else
+            return I2C_ERROR_BUS_BUSY;
+    }
+
     if ((obj_s->XferOperation == I2C_FIRST_AND_LAST_FRAME) ||
         (obj_s->XferOperation == I2C_LAST_FRAME)) {
         if (stop)