From a1e8cedf6b652573ddaff663226c20b3e22a81c3 Mon Sep 17 00:00:00 2001
From: PeterKietzmann <peter.kietzmann@haw-hamburg.de>
Date: Tue, 20 Jan 2015 08:54:40 +0100
Subject: [PATCH] drivers/srf08: Acquire exclusive access to I2C bus

---
 drivers/srf08/srf08.c | 42 +++++++++++++++++++++++++++++++++++++-----
 1 file changed, 37 insertions(+), 5 deletions(-)

diff --git a/drivers/srf08/srf08.c b/drivers/srf08/srf08.c
index 2c178b82ff..dbf131b953 100644
--- a/drivers/srf08/srf08.c
+++ b/drivers/srf08/srf08.c
@@ -21,8 +21,6 @@
  * @}
  */
 
-
-#include <stdbool.h>
 #include <stdint.h>
 #include <stdio.h>
 #include "hwtimer.h"
@@ -35,17 +33,27 @@
 
 int srf08_init(srf08_t *dev, i2c_t i2c, uint8_t addr, i2c_speed_t speed)
 {
+    int status;
+
     dev->i2c = i2c;
     dev->addr = addr;
 
+    /* Acquire exclusive access to the bus. */
+    i2c_acquire(dev->i2c);
     /* initialize i2c interface */
-    if(i2c_init_master(i2c, speed) < 0) {
+    status = i2c_init_master(dev->i2c, speed);
+    /* Release the bus for other threads. */
+    i2c_release(dev->i2c);
+
+    if(status < 0) {
         return -1;
     }
+
     /* set the maximum range */
     if (srf08_set_max_range(dev, SRF08_MAX_RANGE_6M) < 0) {
         return -3;
     }
+
     /* set the maximum gain */
     if (srf08_set_max_gain(dev, SRF08_MAX_GAIN) < 0) {
         return -4;
@@ -57,13 +65,29 @@ int srf08_init(srf08_t *dev, i2c_t i2c, uint8_t addr, i2c_speed_t speed)
 
 int srf08_set_max_range(srf08_t *dev, uint8_t max_range)
 {
-    return i2c_write_reg(dev->i2c, dev->addr, SRF08_RANGE_REG, max_range);
+    int status;
+
+    /* Acquire exclusive access to the bus. */
+    i2c_acquire(dev->i2c);
+    status = i2c_write_reg(dev->i2c, dev->addr, SRF08_RANGE_REG, max_range);
+    /* Release the bus for other threads. */
+    i2c_release(dev->i2c);
+
+    return status;
 }
 
 
 int srf08_set_max_gain(srf08_t *dev, uint8_t gain)
 {
-    return i2c_write_reg(dev->i2c, dev->addr, SRF08_GAIN_REG, gain);
+    int status;
+
+    /* Acquire exclusive access to the bus. */
+    i2c_acquire(dev->i2c);
+    status = i2c_write_reg(dev->i2c, dev->addr, SRF08_GAIN_REG, gain);
+    /* Release the bus for other threads. */
+    i2c_release(dev->i2c);
+
+    return status;
 }
 
 
@@ -75,8 +99,12 @@ int srf08_get_distances(srf08_t *dev, uint16_t *range_array, int num_echos, srf0
     char register_location;
     char max_reg_no_read = (num_echos * sizeof(range_bytes)) +1;
 
+    /* Acquire exclusive access to the bus. */
+    i2c_acquire(dev->i2c);
     /* set ranging mode */
     status = i2c_write_reg(dev->i2c, dev->addr, SRF08_COMMAND_REG, ranging_mode);
+    /* Release the bus for other threads. */
+    i2c_release(dev->i2c);
 
     if (!status) {
         DEBUG("Write the ranging command to the i2c-interface is failed");
@@ -94,8 +122,12 @@ int srf08_get_distances(srf08_t *dev, uint16_t *range_array, int num_echos, srf0
     for (register_location = 2; register_location < max_reg_no_read;
          register_location += sizeof(range_bytes)) {
 
+        /* Acquire exclusive access to the bus. */
+        i2c_acquire(dev->i2c);
         /* read the echo bytes */
         status = i2c_read_regs(dev->i2c, dev->addr, register_location, range_bytes, sizeof(range_bytes));
+        /* Release the bus for other threads. */
+        i2c_release(dev->i2c);
 
         if (!status) {
             DEBUG("Read the echo bytes from the i2c-interface is failed");