spidev fix: don't close spidev if not open before

Signed-off-by: mz-fuzzy <mzfuzzy800@gmail.com>

RF24.cpp

@@ -573,8 +573,6 @@ bool RF24::begin(void)
 
   #if defined (RF24_LINUX)
 
-	SPI();
-    
 	#if defined (MRAA)
 	  GPIO();	
 	  gpio.begin(ce_pin,csn_pin);	

utility/BBB/spi.cpp

@@ -13,8 +13,7 @@
 #include <pthread.h>
 static pthread_mutex_t spiMutex;
 
-SPI::SPI() {
-	
+SPI::SPI():fd(-1) {
 }
 
 void SPI::begin(int busNo){
@@ -51,14 +50,16 @@ void SPI::init()
 {
 	int ret;
     
-    if( !(this->fd > 0)){
+    if (this->fd < 0)  // check whether spi is already open
+    {
 	  this->fd = open(this->device.c_str(), O_RDWR);
-	}
-    if (this->fd < 0)
-	{
-		perror("can't open device");
-		abort();
-	}
+
+      if (this->fd < 0)
+      {
+        perror("can't open device");
+        abort();
+      }
+    }
 
 	/*
 	 * spi mode
@@ -206,6 +207,7 @@ void SPI::transfern(char* buf, uint32_t len)
 
 
 SPI::~SPI() {
-	close(this->fd);
+    if (!(this->fd < 0))
+	    close(this->fd);
 }