gpio: Matured the GPIO API.

* Greater use of return values.
* Uses defined enum instead of char arrays

Signed-off-by: Thomas Ingleby <thomas.c.ingleby@intel.com>

api/gpio.h

@@ -27,21 +27,92 @@
 #include <stdio.h>
 
 #include "maa.h"
-
+/**
+ * A strucutre representing a gpio pin.
+ */
 typedef struct {
-    int pin;
-    int pinMap;
-    char path[64];
-    FILE *value_fp;
+    /*@{*/
+    int pin; /**< the pin number, as known to the os. */
+    FILE *value_fp; /**< the file pointer to the value of the gpio /*
+    /*@}*/
 } maa_gpio_context;
 
-typedef char gpio_mode_t[16];
-typedef char gpio_dir_t[16];
+/**
+ * GPIO Output modes
+ */
+typedef enum {
+    MAA_GPIO_STRONG     = 0, /**< Default. Strong high and low */
+    MAA_GPIO_PULLUP     = 1, /**< Resistive High */
+    MAA_GPIO_PULLDOWN   = 2, /**< Resistive Low */
+    MAA_GPIO_HIZ        = 3  /**< High Z State */
+} gpio_mode_t;
 
+/**
+ * GPIO Direction options.
+ */
+typedef enum {
+    MAA_GPIO_OUT    = 0, /**< Output. A Mode can also be set */
+    MAA_GPIO_IN     = 1  /**< Input. */
+} gpio_dir_t;
+
+/** Initialise gpio_context, based on board number
+ *
+ *  @param pin pin number read from the board, i.e IO3 is 3.
+ *
+ *  @returns
+ *       maa_gpio_context based on the IO pin
+ */
 maa_gpio_context* maa_gpio_init(int pin);
-void maa_gpio_mode(maa_gpio_context *dev, gpio_mode_t mode);
-void maa_gpio_dir(maa_gpio_context *dev, gpio_dir_t dir);
 
-void maa_gpio_close(maa_gpio_context *dev);
+/** Initialise gpio context without any mapping to a pin.
+ * - For more expert users
+ *
+ * @param gpiopin gpio pin as listed in SYSFS
+ *
+ * @return gpio context
+ */
+maa_gpio_context* maa_gpio_init_raw(int gpiopin);
+
+/** Set GPIO Output Mode,
+ *
+ * @param dev The GPIO context
+ * @param mode The GPIO Output Mode.
+ *
+ * @return maa result type.
+ */
+maa_result_t maa_gpio_mode(maa_gpio_context *dev, gpio_mode_t mode);
+
+/** Set GPIO direction
+ *
+ * @param dev The GPIO context.
+ * @param dir The direction of the GPIO.
+ *
+ * @return maa result type.
+ */
+maa_result_t maa_gpio_dir(maa_gpio_context *dev, gpio_dir_t dir);
+
+/** Close the GPIO context
+ * - Will free the memory for the context.
+ *
+ * @param dev the GPIO context
+ *
+ * @return maa result type.
+ */
+maa_result_t maa_gpio_close(maa_gpio_context *dev);
+
+/** Read the GPIO value.
+ *
+ * @param dev The GPIO context.
+ *
+ * @return the integer value of the GPIO
+ */
 int maa_gpio_read(maa_gpio_context *dev);
-void maa_gpio_write(maa_gpio_context *dev, int value);
+
+/** Write to the GPIO Value.
+ *
+ * @param dev The GPIO context.
+ * @param value Integer value to write.
+ *
+ * @return maa result type
+ */
+maa_result_t maa_gpio_write(maa_gpio_context *dev, int value);

src/gpio/gpio.c

@@ -43,12 +43,20 @@ maa_gpio_get_valfp(maa_gpio_context *dev)
 
 maa_gpio_context*
 maa_gpio_init(int pin)
+{
+    //TODO
+    return NULL;
+}
+
+maa_gpio_context*
+maa_gpio_init_raw(int pin)
 {
     FILE *export_f;
     maa_gpio_context* dev = (maa_gpio_context*) malloc(sizeof(maa_gpio_context));
 
     if ((export_f = fopen("/sys/class/gpio/export", "w")) == NULL) {
         fprintf(stderr, "Failed to open export for writing!\n");
+        return NULL;
     } else {
         fprintf(export_f, "%d", pin);
         fclose(export_f);
@@ -57,13 +65,13 @@ maa_gpio_init(int pin)
     return dev;
 }
 
-void
+maa_result_t
 maa_gpio_mode(maa_gpio_context *dev, gpio_mode_t mode)
 {
-    //gpio->pin
+    return MAA_ERROR_FEATURE_NOT_IMPLEMENTED;
 }
 
-void
+maa_result_t
 maa_gpio_dir(maa_gpio_context *dev, gpio_dir_t dir)
 {
     if (dev->value_fp != NULL) {
@@ -75,11 +83,23 @@ maa_gpio_dir(maa_gpio_context *dev, gpio_dir_t dir)
     FILE *direction;
     if ((direction = fopen(filepath, "w")) == NULL) {
         fprintf(stderr, "Failed to open direction for writing!\n");
-    } else {
-        fprintf(direction, dir);
-        fclose(direction);
-        dev->value_fp = NULL;
+        return MAA_ERROR_INVALID_RESOURCE;
     }
+    switch(dir) {
+        case MAA_GPIO_OUT:
+            fprintf(direction, "out");
+            break;
+        case MAA_GPIO_IN:
+            fprintf(direction, "in");
+            break;
+        default:
+            fclose(direction);
+            return MAA_ERROR_FEATURE_NOT_IMPLEMENTED;
+            break;
+    }
+    fclose(direction);
+    dev->value_fp = NULL;
+    return MAA_SUCCESS;
 }
 
 int
@@ -95,7 +115,7 @@ maa_gpio_read(maa_gpio_context *dev)
     return atoi(buffer);
 }
 
-void
+maa_result_t
 maa_gpio_write(maa_gpio_context *dev, int value)
 {
     if (dev->value_fp == NULL) {
@@ -104,18 +124,24 @@ maa_gpio_write(maa_gpio_context *dev, int value)
     fseek(dev->value_fp, SEEK_SET, 0);
     fprintf(dev->value_fp, "%d", value);
     fseek(dev->value_fp, SEEK_SET, 0);
-
+    if (ferror(dev->value_fp) != 0)
+        return MAA_ERROR_INVALID_RESOURCE;
+    return MAA_SUCCESS;
 }
 
-void
+maa_result_t
 maa_gpio_close(maa_gpio_context *dev)
 {
     FILE *unexport_f;
 
     if ((unexport_f = fopen("/sys/class/gpio/unexport", "w")) == NULL) {
         fprintf(stderr, "Failed to open unexport for writing!\n");
-    } else {
-        fprintf(unexport_f, "%d", dev->pin);
-        fclose(unexport_f);
+        return MAA_ERROR_INVALID_RESOURCE;
     }
+    fprintf(unexport_f, "%d", dev->pin);
+    fclose(unexport_f);
+    if (ferror(dev->value_fp) != 0)
+        return MAA_ERROR_INVALID_RESOURCE;
+    free(dev);
+    return MAA_SUCCESS;
 }