Flesh out unfinished lock() method implementations in al SPI drivers

arch/z80/src/ez80/ez80_spi.c

@@ -1,7 +1,7 @@
 /****************************************************************************
  * arch/z80/src/ez80/ez80_spi.c
  *
- *   Copyright (C) 2009-2010 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2009-2010, 2016 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <gnutt@nuttx.org>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -41,6 +41,8 @@
 
 #include <sys/types.h>
 #include <stdint.h>
+#include <semaphore.h>
+#include <assert.h>
 #include <errno.h>
 
 #include <arch/board/board.h>
@@ -85,33 +87,32 @@ static void   spi_recvblock(FAR struct spi_dev_s *dev, FAR uint8_t *buffer,
 static const struct spi_ops_s g_spiops =
 {
   spi_lock,
-  ez80_spiselect,    /* select: Provided externally by board logic */
+  ez80_spiselect,      /* select: Provided externally by board logic */
   spi_setfrequency,
   spi_setmode,
-  NULL,              /* setbits: Variable number of bits not implemented */
+  NULL,                /* setbits: Variable number of bits not implemented */
 #ifdef CONFIG_SPI_HWFEATURES
-  NULL,              /* hwfeatures: Not supported */
+  NULL,                /* hwfeatures: Not supported */
 #endif
-  ez80_spistatus,    /* status: Provided externally by board logic */
+  ez80_spistatus,      /* status: Provided externally by board logic */
 #ifdef CONFIG_SPI_CMDDATA
   ez80_spicmddata,
 #endif
   spi_send,
   spi_sndblock,
   spi_recvblock,
-  0                  /* registercallback: Not yet implemented */
+  0                    /* registercallback: Not yet implemented */
 };
 
 /* This supports is only a single SPI bus/port.  If you port this to an
- * architecture with multiple SPI busses/ports, then the following must
- * become an array with one 'struct spi_dev_s' instance per bus.
+ * architecture with multiple SPI busses/ports, then (1) you must create
+ * a structure, say ez80_spidev_s, containing both struct spi_dev_s and
+ * the mutual exclusion semaphored, and (2) the following must become an
+ * array with one 'struct spi_dev_s' instance per bus.
  */
 
-static struct spi_dev_s g_spidev = { &g_spiops };
-
-/****************************************************************************
- * Public Data
- ****************************************************************************/
+static struct spi_dev_s g_spidev = {&g_spiops};
+static sem_t g_exclsem = SEM_INITIALIZER(1);  /* For mutually exclusive access */
 
 /****************************************************************************
  * Private Functions
@@ -140,9 +141,25 @@ static struct spi_dev_s g_spidev = { &g_spiops };
 
 static int spi_lock(FAR struct spi_dev_s *dev, bool lock)
 {
-  /* Not implemented */
+  if (lock)
+    {
+      /* Take the semaphore (perhaps waiting) */
 
-  return -ENOSYS;
+      while (sem_wait(&g_exclsem) != 0)
+        {
+          /* The only case that an error should occur here is if the wait
+           * was awakened by a signal.
+           */
+
+          DEBUGASSERT(errno == EINTR);
+        }
+    }
+  else
+    {
+      (void)sem_post(&g_exclsem);
+    }
+
+  return OK;
 }
 
 /****************************************************************************