swig: Add support for isr/callbacks from python

Signed-off-by: Brendan Le Foll <brendan.le.foll@intel.com>

api/gpio.h

@@ -34,6 +34,10 @@
 extern "C" {
 #endif
 
+#ifdef SWIG
+#include <Python.h>
+#endif
+
 #include <stdio.h>
 #include <pthread.h>
 
@@ -46,7 +50,11 @@ typedef struct {
     /*@{*/
     int pin; /**< the pin number, as known to the os. */
     int value_fp; /**< the file pointer to the value of the gpio */
+#ifdef SWIG
+    PyObject *isr; /**< the interupt service request */
+#else
     void (* isr)(); /**< the interupt service request */
+#endif
     pthread_t thread_id; /**< the isr handler thread id */
     int isr_value_fp; /**< the isr file pointer on the value */
     /*@}*/

examples/python/hello_isr.py

@@ -0,0 +1,10 @@
+#!/usr/bin/env python
+
+import pymaa as maa
+
+def test():
+  print("wooo")
+
+x = maa.Gpio(6)
+x.dir(maa.MAA_GPIO_IN)
+x.set_isr(test)

src/gpio/gpio.c

@@ -124,7 +124,19 @@ maa_gpio_interrupt_handler(void* arg)
     for (;;) {
         ret = maa_gpio_wait_interrupt(dev->isr_value_fp);
         if (ret == MAA_SUCCESS) {
+#ifdef SWIG
+            // In order to call a python object (all python functions are objects) we
+            // need to aquire the GIL (Global Interpreter Lock). This may not always be
+            // nessecary but especially if doing IO (like print()) python will segfault
+            // if we do not hold a lock on the GIL
+            PyGILState_STATE gilstate = PyGILState_Ensure();
+
+            PyEval_CallObject(dev->isr, NULL);
+
+            PyGILState_Release (gilstate);
+#else
             dev->isr();
+#endif
         } else {
 	    // we must have got an error code so die nicely
             close(dev->isr_value_fp);
@@ -190,6 +202,11 @@ maa_gpio_isr_exit(maa_gpio_context *dev)
 {
     maa_result_t ret = MAA_SUCCESS;
 
+#ifdef SWIG
+    // Dereference our Python call back function
+    Py_DECREF(dev->isr);
+#endif
+
     if (dev->thread_id == 0) {
         return ret;
     }

src/maa.c

@@ -55,6 +55,12 @@ maa_init()
     if (plat != NULL) {
         return MAA_ERROR_PLATFORM_ALREADY_INITIALISED;
     }
+#ifdef SWIG
+    // Initialise python threads, this allows use to grab the GIL when we are
+    // required to do so
+    Py_InitializeEx(0);
+    PyEval_InitThreads();
+#endif
     plat = maa_intel_galileo_rev_d();
     return MAA_SUCCESS;
 }

src/maa.i

@@ -8,6 +8,7 @@
 %}
 
 %init %{
+    //Adding maa_init() to the module initialisation process
     maa_init();
 %}
 
@@ -45,9 +46,19 @@ typedef struct {
     /*@{*/
     int pin; /**< the pin number, as known to the os. */
     FILE *value_fp; /**< the file pointer to the value of the gpio */
+#if defined(SWIGPYTHON)
+    PyObject *isr; /**< the interupt service request */
+#endif
+    pthread_t thread_id; /**< the isr handler thread id */
+    int isr_value_fp; /**< the isr file pointer on the value */
     /*@}*/
 } maa_gpio_context;
 
+%typemap(check) PyObject *pyfunc {
+  if (!PyCallable_Check($1))
+    SWIG_exception(SWIG_TypeError,"Expected function.");
+}
+
 %extend maa_gpio_context {
   maa_gpio_context(int pin, int raw=0)
   {
@@ -95,6 +106,22 @@ typedef struct {
   {
     return maa_gpio_mode($self, mode);
   }
+#if defined(SWIGPYTHON)
+  //set python method as the isr function
+  int set_isr(PyObject *pyfunc)
+  {
+    Py_INCREF(pyfunc);
+    // do a nasty cast to get away from the warnings
+    maa_gpio_isr(self, MAA_GPIO_EDGE_BOTH, pyfunc);
+    return 0;
+  }
+#else
+  %ignore maa_gpio_isr;
+#endif
+  int isr_exit()
+  {
+    maa_gpio_isr_exit(self);
+  }
 }
 
 #### i2c ####

src/python/CMakeLists.txt

@@ -9,6 +9,8 @@ include_directories(
 swig_add_module (pymaa python pymaa.i ${maa_LIB_SRCS})
 swig_link_libraries (pymaa ${PYTHON_LIBRARIES})
 
+set (CMAKE_C_FLAGS -DSWIG=${SWIG_FOUND})
+
 if (DOXYGEN_FOUND)
   foreach (_file ${DOCFILES})
     add_dependencies (${SWIG_MODULE_pymaa_REAL_NAME} ${_file}doc_i)