From 2864cce6d7a097112af4db08c83bed0f0f68d44d Mon Sep 17 00:00:00 2001
From: PeterKietzmann <peter.kietzmann@haw-hamburg.de>
Date: Thu, 29 Jan 2015 09:55:57 +0100
Subject: [PATCH] drivers/lps331ap: Acquire exclusice access to I2C bus

---
 drivers/lps331ap/lps331ap.c | 30 ++++++++++++++++++++++++++++--
 1 file changed, 28 insertions(+), 2 deletions(-)

diff --git a/drivers/lps331ap/lps331ap.c b/drivers/lps331ap/lps331ap.c
index ad17c234a8..86179f77da 100644
--- a/drivers/lps331ap/lps331ap.c
+++ b/drivers/lps331ap/lps331ap.c
@@ -18,12 +18,14 @@
  *       used.
  *
  * @author      Hauke Petersen <hauke.petersen@fu-berlin.de>
+ * @author      Peter Kietzmann <peter.kietzmann@haw-hamburg.de>
  *
  * @}
  */
 
 #include <stdint.h>
 
+#include "mutex.h"
 #include "periph/i2c.h"
 #include "lps331ap.h"
 #include "lps331ap-internal.h"
@@ -53,8 +55,12 @@ int lps331ap_init(lps331ap_t *dev, i2c_t i2c, uint8_t address, lps331ap_rate_t r
     dev->i2c = i2c;
     dev->address = address;
 
+    /* Acquire exclusive access to the bus. */
+    i2c_acquire(dev->i2c);
     /* initialize underlying I2C bus */
     if (i2c_init_master(dev->i2c, BUS_SPEED) < 0) {
+        /* Release the bus for other threads. */
+        i2c_release(dev->i2c);
         return -1;
     }
 
@@ -62,8 +68,10 @@ int lps331ap_init(lps331ap_t *dev, i2c_t i2c, uint8_t address, lps331ap_rate_t r
     tmp = LPS331AP_CTRL_REG1_DBDU | LPS331AP_CTRL_REG1_PD |
           (rate << LPS331AP_CTRL_REG1_ODR_POS);
     if (i2c_write_reg(dev->i2c, dev->address, LPS331AP_REG_CTRL_REG1, tmp) != 1) {
+        i2c_release(dev->i2c);
         return -1;
     }
+    i2c_release(dev->i2c);
 
     return 0;
 }
@@ -74,9 +82,11 @@ int lps331ap_read_temp(lps331ap_t *dev)
     int16_t val = 0;
     float res = TEMP_BASE;      /* reference value -> see datasheet */
 
+    i2c_acquire(dev->i2c);
     i2c_read_reg(dev->i2c, dev->address, LPS331AP_REG_TEMP_OUT_L, &tmp);
     val |= tmp;
     i2c_read_reg(dev->i2c, dev->address, LPS331AP_REG_TEMP_OUT_H, &tmp);
+    i2c_release(dev->i2c);
     val |= (tmp << 8);
 
     /* compute actual temperature value in °C */
@@ -92,11 +102,13 @@ int lps331ap_read_pres(lps331ap_t *dev)
     int32_t val = 0;
     float res;
 
+    i2c_acquire(dev->i2c);
     i2c_read_reg(dev->i2c, dev->address, LPS331AP_REG_PRESS_OUT_XL, &tmp);
     val |= tmp;
     i2c_read_reg(dev->i2c, dev->address, LPS331AP_REG_PRESS_OUT_L, &tmp);
     val |= (tmp << 8);
     i2c_read_reg(dev->i2c, dev->address, LPS331AP_REG_PRESS_OUT_H, &tmp);
+    i2c_release(dev->i2c);
     val |= (tmp << 16);
     /* see if value is negative */
     if (tmp & 0x80) {
@@ -113,19 +125,33 @@ int lps331ap_read_pres(lps331ap_t *dev)
 int lps331ap_enable(lps331ap_t *dev)
 {
     char tmp;
+    int status;
+
+    i2c_acquire(dev->i2c);
     if (i2c_read_reg(dev->i2c, dev->address, LPS331AP_REG_CTRL_REG1, &tmp) != 1) {
+        i2c_release(dev->i2c);
         return -1;
     }
     tmp |= (LPS331AP_CTRL_REG1_PD);
-    return i2c_write_reg(dev->i2c, dev->address, LPS331AP_REG_CTRL_REG1, tmp);
+    status = i2c_write_reg(dev->i2c, dev->address, LPS331AP_REG_CTRL_REG1, tmp);
+    i2c_release(dev->i2c);
+
+    return status;
 }
 
 int lps331ap_disable(lps331ap_t *dev)
 {
     char tmp;
+    int status;
+
+    i2c_acquire(dev->i2c);
     if (i2c_read_reg(dev->i2c, dev->address, LPS331AP_REG_CTRL_REG1, &tmp) != 1) {
+        i2c_release(dev->i2c);
         return -1;
     }
     tmp &= ~(LPS331AP_CTRL_REG1_PD);
-    return i2c_write_reg(dev->i2c, dev->address, LPS331AP_REG_CTRL_REG1, tmp);
+    status = i2c_write_reg(dev->i2c, dev->address, LPS331AP_REG_CTRL_REG1, tmp);
+    i2c_release(dev->i2c);
+
+    return status;
 }