netdev_driver: get/set power with signed values

Author: pnunes30

stack/framework/hal/chips/netdev_driver/inc/sx127x.h

@@ -209,7 +209,7 @@ typedef struct {
 typedef struct {
     uint16_t preamble_len;             /**< Length of preamble header */
     uint8_t sync_len;                  /**< Length of sync word */
-    uint8_t power;                     /**< Signal power */
+    int8_t power;                      /**< Signal power */
     uint8_t bandwidth;                 /**< Signal bandwidth */
     uint8_t datarate;                  /**< bitrate in bps */
 
@@ -662,7 +662,7 @@ void sx127x_set_payload_length(sx127x_t *dev, uint16_t len);
  *
  * @return the radio power
  */
-uint8_t sx127x_get_tx_power(const sx127x_t *dev);
+int8_t sx127x_get_tx_power(const sx127x_t *dev);
 
 /**
  * @brief   Sets the SX127X transmission power

stack/framework/hal/chips/netdev_driver/sx127x_getset.c

@@ -1051,7 +1051,7 @@ static inline uint8_t sx127x_get_pa_select(const sx127x_t *dev)
     return SX127X_RF_PACONFIG_PASELECT_RFO;
 }
 
-uint8_t sx127x_get_tx_power(const sx127x_t *dev)
+int8_t sx127x_get_tx_power(const sx127x_t *dev)
 {
     switch (dev->settings.modem) {
         case SX127X_MODEM_FSK:

stack/framework/hal/chips/netdev_driver/sx127x_netdev.c

@@ -475,8 +475,8 @@ static int _get(netdev_t *netdev, netopt_t opt, void *val, size_t max_len)
             return sizeof(netopt_enable_t);
 
         case NETOPT_TX_POWER:
-            assert(max_len >= sizeof(int16_t));
-            *((int16_t*) val) = (int16_t)sx127x_get_tx_power(dev);
+            assert(max_len >= sizeof(int8_t));
+            *((int8_t*) val) = sx127x_get_tx_power(dev);
             return sizeof(int16_t);
 
         case NETOPT_IQ_INVERT:
@@ -671,8 +671,8 @@ static int _set(netdev_t *netdev, netopt_t opt, const void *val, size_t len)
                 res = -EINVAL;
                 break;
             }
-            sx127x_set_tx_power(dev, (int8_t)power);
-            return sizeof(int16_t);
+            sx127x_set_tx_power(dev, power);
+            return sizeof(int8_t);
 
         case NETOPT_FIXED_HEADER:
             assert(len <= sizeof(netopt_enable_t));