Added block-level spi writes

/** Write to the SPI Slave and obtain the response
 *
 *  The total number of bytes sent and recieved will be the maximum of
 *  outlength and inlength. The bytes written will be padded with the
 *  value 0xff.
 *
 *  @param outdata Pointer to the byte-array of data to write to the device
 *  @param outlength Number of bytes to write
 *  @param indata Pointer to the byte-array of data to read from the device
 *  @param inlength Number of bytes to read from the device
 *  @returns
 *      The number of bytes written and read from the device. This is
 *      maximum of outlength and inlength.
 */
virtual int write(const char *outdata, int outlength,
        char *indata, int inlength);

drivers/SPI.cpp

@@ -78,6 +78,23 @@ int SPI::write(int value) {
     return ret;
 }
 
+int SPI::write(const char *outdata, int outlength, char *indata, int inlength) {
+    int total = (outlength > inlength) ? outlength : inlength;
+
+    lock();
+    aquire();
+    for (int i = 0; i < total; i++) {
+        char out = (i < outlength) ? outdata[i] : 0xff;
+        char in = spi_master_write(&_spi, out);
+        if (i < inlength) {
+            indata[i] = in;
+        }
+    }
+    unlock();
+
+    return total;
+}
+
 void SPI::lock() {
     _mutex->lock();
 }

drivers/SPI.h

@@ -115,9 +115,25 @@ class SPI {
      *
      *  @returns
      *    Response from the SPI slave
-    */
+     */
     virtual int write(int value);
 
+    /** Write to the SPI Slave and obtain the response
+     *
+     *  The total number of bytes sent and recieved will be the maximum of
+     *  outlength and inlength. The bytes written will be padded with the
+     *  value 0xff.
+     *
+     *  @param outdata Pointer to the byte-array of data to write to the device
+     *  @param outlength Number of bytes to write
+     *  @param indata Pointer to the byte-array of data to read from the device
+     *  @param inlength Number of bytes to read from the device
+     *  @returns
+     *      The number of bytes written and read from the device. This is
+     *      maximum of outlength and inlength.
+     */
+    virtual int write(const char *outdata, int outlength, char *indata, int inlength);
+
     /** Acquire exclusive access to this SPI bus
      */
     virtual void lock(void);