SensorManager: accel: implement accelerometer data polling via /sys/bus/iio

for simplicity, we currently just take the first device in `/sys/bus/iio/devices`
that looks like an accelerometer.

src/api-impl-jni/generated_headers/android_hardware_SensorManager.h

@@ -10,10 +10,10 @@ extern "C" {
 /*
  * Class:     android_hardware_SensorManager
  * Method:    register_accelerometer_listener_native
- * Signature: (Landroid/hardware/SensorEventListener;Landroid/hardware/Sensor;)V
+ * Signature: (Landroid/hardware/SensorEventListener;Landroid/hardware/Sensor;I)V
  */
 JNIEXPORT void JNICALL Java_android_hardware_SensorManager_register_1accelerometer_1listener_1native
-  (JNIEnv *, jobject, jobject, jobject);
+  (JNIEnv *, jobject, jobject, jobject, jint);
 
 #ifdef __cplusplus
 }

src/api-impl-jni/sensors/android_hardware_SensorManager.c

@@ -1,23 +1,42 @@
+#include <graphene.h>
 #include <libportal/portal.h>
+#include <sys/param.h>
 
 #include "../defines.h"
 #include "../util.h"
 #include "../generated_headers/android_hardware_SensorManager.h"
 
-/* FIXME */
+struct iio_accel_files {
-float x = 0;
+	GString *in_accel_x_raw;
-float y = 2;
+	GString *in_accel_y_raw;
-float z = 0;
+	GString *in_accel_z_raw;
+	GString *in_accel_scale;
+	GString *in_mount_matrix;
+};
 
-struct accel_callback_data { JavaVM *jvm; jobject listener; jclass listener_class; jobject sensor; };
+struct accel_callback_data { JavaVM *jvm; jobject listener; jclass listener_class; jobject sensor; struct iio_accel_files *iio_accel_files; graphene_matrix_t *matrix; };
 gboolean on_accel_data(struct accel_callback_data *d)
 {
 	JNIEnv *env;
 	(*d->jvm)->GetEnv(d->jvm, (void**)&env, JNI_VERSION_1_6);
 
-	jfloatArray values = (*env)->NewFloatArray(env, 3);
+	char *x_str;
-	(*env)->SetFloatArrayRegion(env, values, 0, 3, (jfloat[]){x, y, z});
+	char *y_str;
+	char *z_str;
+	char *scale_str;
 
+	g_file_get_contents(d->iio_accel_files->in_accel_x_raw->str, &x_str, NULL, NULL);
+	g_file_get_contents(d->iio_accel_files->in_accel_y_raw->str, &y_str, NULL, NULL);
+	g_file_get_contents(d->iio_accel_files->in_accel_z_raw->str, &z_str, NULL, NULL);
+	g_file_get_contents(d->iio_accel_files->in_accel_scale->str, &scale_str, NULL, NULL);
+	graphene_vec3_t *vector = graphene_vec3_alloc();
+	graphene_vec3_init(vector, atof(x_str), atof(y_str), atof(z_str));
+	graphene_vec3_scale(vector, (-1) * atof(scale_str), vector); // multiply by -1 to get what android expects
+	graphene_matrix_transform_vec3(d->matrix, vector, vector);
+
+	jfloatArray values = (*env)->NewFloatArray(env, 3);
+	(*env)->SetFloatArrayRegion(env, values, 0, 3, (jfloat[]){graphene_vec3_get_x(vector), graphene_vec3_get_y(vector), graphene_vec3_get_z(vector)});
+	graphene_vec3_free(vector);
 	jobject sensor_event = (*env)->NewObject(env, handle_cache.sensor_event.class, handle_cache.sensor_event.constructor, values, d->sensor);
 
 	(*env)->CallVoidMethod(env, d->listener, _METHOD(d->listener_class, "onSensorChanged", "(Landroid/hardware/SensorEvent;)V"), sensor_event);
@@ -27,16 +46,95 @@ gboolean on_accel_data(struct accel_callback_data *d)
 	return G_SOURCE_CONTINUE;
 }
 
-JNIEXPORT void JNICALL Java_android_hardware_SensorManager_register_1accelerometer_1listener_1native(JNIEnv *env , jobject this, jobject listener, jobject sensor)
+graphene_matrix_t *get_mount_matrix(char *mount_matrix_path)
+{
+	graphene_matrix_t *matrix = NULL;
+
+	char *matrix_str;
+	g_file_get_contents(mount_matrix_path, &matrix_str, NULL, NULL);
+
+	float matrix_f[] = {1, 0, 0, 0,
+		            0, 1, 0, 0,
+		            0, 0, 1, 0,
+		            0, 0, 0, 1};
+
+	sscanf(matrix_str, "%f, %f, %f; %f, %f, %f; %f, %f, %f", &matrix_f[0], &matrix_f[1], &matrix_f[2],
+		                                                 &matrix_f[4], &matrix_f[5], &matrix_f[6],
+		                                                 &matrix_f[8], &matrix_f[9], &matrix_f[10]);
+	matrix = graphene_matrix_alloc();
+	graphene_matrix_init_from_float(matrix, matrix_f);
+
+	return matrix;
+}
+
+struct iio_accel_files *get_iio_accel_files(void)
+{
+	GError *error = NULL;
+	const gchar *iio_device_path;
+	bool found_accelerometer = false;
+
+	GDir *iio_dir = g_dir_open("/sys/bus/iio/devices", 0, &error);
+	if(!iio_dir) {
+		g_log(NULL, G_LOG_LEVEL_WARNING, "cannot register accelerometer listener: cannot open /sys/bus/iio/devices (error: %s)", error->message);
+		return NULL;
+	}
+
+	struct iio_accel_files *iio_accel_files = malloc(sizeof(struct iio_accel_files));
+	iio_accel_files->in_accel_x_raw = g_string_new(NULL);
+	iio_accel_files->in_accel_y_raw = g_string_new(NULL);
+	iio_accel_files->in_accel_z_raw = g_string_new(NULL);
+	iio_accel_files->in_accel_scale = g_string_new(NULL);
+	iio_accel_files->in_mount_matrix = g_string_new(NULL);
+
+	while ((iio_device_path = g_dir_read_name(iio_dir))) {
+		g_string_printf(iio_accel_files->in_accel_x_raw, "/sys/bus/iio/devices/%s/in_accel_x_raw", iio_device_path);
+		g_string_printf(iio_accel_files->in_accel_y_raw, "/sys/bus/iio/devices/%s/in_accel_y_raw", iio_device_path);
+		g_string_printf(iio_accel_files->in_accel_z_raw, "/sys/bus/iio/devices/%s/in_accel_z_raw", iio_device_path);
+		g_string_printf(iio_accel_files->in_accel_scale, "/sys/bus/iio/devices/%s/in_accel_scale", iio_device_path);
+		g_string_printf(iio_accel_files->in_mount_matrix, "/sys/bus/iio/devices/%s/in_mount_matrix", iio_device_path);
+		if(g_file_test(iio_accel_files->in_accel_x_raw->str, G_FILE_TEST_IS_REGULAR)
+		   && g_file_test(iio_accel_files->in_accel_y_raw->str, G_FILE_TEST_IS_REGULAR)
+		   && g_file_test(iio_accel_files->in_accel_z_raw->str, G_FILE_TEST_IS_REGULAR)
+		   && g_file_test(iio_accel_files->in_accel_scale->str, G_FILE_TEST_IS_REGULAR)
+		   && g_file_test(iio_accel_files->in_mount_matrix->str, G_FILE_TEST_IS_REGULAR)) {
+			found_accelerometer = true;
+			break;
+		}
+	}
+
+	g_dir_close(iio_dir);
+
+	if(!found_accelerometer) {
+		g_log(NULL, G_LOG_LEVEL_WARNING, "cannot register accelerometer listener: haven't found an iio accelerometer");
+		g_string_free(iio_accel_files->in_accel_x_raw, true);
+		g_string_free(iio_accel_files->in_accel_y_raw, true);
+		g_string_free(iio_accel_files->in_accel_z_raw, true);
+		g_string_free(iio_accel_files->in_accel_scale, true);
+		g_string_free(iio_accel_files->in_mount_matrix, true);
+		free(iio_accel_files);
+		return NULL;
+	}
+
+	return iio_accel_files;
+}
+
+JNIEXPORT void JNICALL Java_android_hardware_SensorManager_register_1accelerometer_1listener_1native(JNIEnv *env , jobject this, jobject listener, jobject sensor, jint sampling_period)
 {
 	JavaVM *jvm;
 	(*env)->GetJavaVM(env, &jvm);
 
+	struct iio_accel_files *iio_accel_files = get_iio_accel_files();
+	if(!iio_accel_files)
+		return;
+
 	struct accel_callback_data *callback_data = malloc(sizeof(struct accel_callback_data));
 	callback_data->jvm = jvm;
  	callback_data->listener = _REF(listener);
 	callback_data->listener_class = _REF(_CLASS(callback_data->listener));
 	callback_data->sensor = _REF(sensor);
+	callback_data->iio_accel_files = iio_accel_files;
+	callback_data->matrix = get_mount_matrix(iio_accel_files->in_mount_matrix->str);
 
-	g_timeout_add(10, G_SOURCE_FUNC(on_accel_data), callback_data);
+	/* FIXME: too short of a sampling period can lock up the process */
+	g_timeout_add(MAX(10, sampling_period), G_SOURCE_FUNC(on_accel_data), callback_data);
 }

src/api-impl/android/hardware/SensorManager.java

@@ -28,7 +28,7 @@ public class SensorManager {
 				});
 				return true;
 			case Sensor.TYPE_ACCELEROMETER:
-				register_accelerometer_listener_native(listener, sensor);
+				register_accelerometer_listener_native(listener, sensor, samplingPeriodUs);
 				return true;
 			default:
 				return false;
@@ -43,5 +43,5 @@ public class SensorManager {
 		System.out.println("STUB: andoroid.hw.SensorManager.unregisterListener");
 	}
 
-	native void register_accelerometer_listener_native(SensorEventListener listener, Sensor sensor);
+	native void register_accelerometer_listener_native(SensorEventListener listener, Sensor sensor, int sampling_period);
 }