convertablet/daemon/accel_monitor.c

#include "accel_monitor.h"

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

static char* sensor_get_axis_path(char const* const base, char axis)
{
	// TODO: Be smarter about the buffer size
	char buffer[128];
	snprintf(buffer, sizeof(buffer), "%s/in_accel_%c_raw", base, axis);
	return strdup(buffer);
}

static int monitor_thread(void* data)
{
	struct accel_monitor* monitor = data;

	while (!monitor->monitoring_thread_is_ready)
		;

	char* x_axis_path = sensor_get_axis_path(monitor->sysfs_device_path, 'x');
	FILE* x_axis_fp   = fopen(x_axis_path, "r");
	free(x_axis_path);

	char* y_axis_path = sensor_get_axis_path(monitor->sysfs_device_path, 'y');
	FILE* y_axis_fp   = fopen(y_axis_path, "r");
	free(y_axis_path);

	char* z_axis_path = sensor_get_axis_path(monitor->sysfs_device_path, 'z');
	FILE* z_axis_fp   = fopen(z_axis_path, "r");
	free(z_axis_path);

	while (!monitor->monitoring_thread_should_exit) {
		fseek(x_axis_fp, 0, SEEK_SET);
		fseek(y_axis_fp, 0, SEEK_SET);
		fseek(z_axis_fp, 0, SEEK_SET);

		int16_t x_axis;
		int16_t y_axis;
		int16_t z_axis;

		fscanf(x_axis_fp, "%hd\n", &x_axis);
		fscanf(y_axis_fp, "%hd\n", &y_axis);
		fscanf(z_axis_fp, "%hd\n", &z_axis);

		if (mtx_lock(&monitor->current_data_lock) != thrd_success) {
			fprintf(stderr,
			        "Can't lock data from data monitoring thread. Something is "
			        "going wrong. Giving up on monitoring sensor data.\n");
			break;
		}

		monitor->current_data.x = x_axis;
		monitor->current_data.y = y_axis;
		monitor->current_data.z = z_axis;

		if (mtx_unlock(&monitor->current_data_lock) != thrd_success) {
			fprintf(stderr,
			        "Can't unlock data from data monitoring thread. Something "
			        "is going wrong. Giving up on monitoring sensor data.\n");
			break;
		}

		monitor->data_is_ready = true;
	}

	fclose(x_axis_fp);
	fclose(y_axis_fp);
	fclose(z_axis_fp);

	return 0;
}

struct accel_monitor* accel_start_monitor(char const* const sysfs_device_path)
{
	mtx_t current_data_lock;
	if (mtx_init(&current_data_lock, mtx_plain) != thrd_success) return 0;

	if (mtx_lock(&current_data_lock) != thrd_success) return 0;

	struct accel_monitor* monitor = calloc(1, sizeof(struct accel_monitor));

	monitor->monitoring_thread_is_ready = false;
	monitor->data_is_ready              = false;

	thrd_t monitoring_thread;
	if (thrd_create(&monitoring_thread, &monitor_thread, monitor) !=
	    thrd_success) {
		free(monitor);
		return 0;
	}

	monitor->sysfs_device_path = sysfs_device_path;
	monitor->monitoring_thread = monitoring_thread;
	monitor->current_data_lock = current_data_lock;

	monitor->current_data.x = 0;
	monitor->current_data.y = 0;
	monitor->current_data.z = 0;

	monitor->monitoring_thread_should_exit = false;

	if (mtx_unlock(&monitor->current_data_lock) != thrd_success)
		fprintf(stderr,
		        "Unable to unlock the data after initialisation. We are in UB "
		        "territory. Something must've went very wrong\n");

	monitor->monitoring_thread_is_ready = true;

	return monitor;
}

static bool axis_is_near_0(int16_t axis)
{
	return (axis > -500) && (axis < 500);
}

static bool axis_is_mostly_positive(int16_t axis)
{
	return axis >= 500;
}

static bool axis_is_mostly_negative(int16_t axis)
{
	return axis <= -500;
}

enum accel_rotation accel_get_current_rotation(struct accel_monitor* monitor)
{
	if (mtx_lock(&monitor->current_data_lock) != thrd_success)
		return ACCEL_ROTATION_NO_CHANGE;
	struct accel_data data = monitor->current_data;
	if (mtx_unlock(&monitor->current_data_lock) != thrd_success)
		fprintf(stderr, "Can't unlock data, this is going to cause issues.\n");

	if (axis_is_near_0(data.x)) {
		if (axis_is_mostly_positive(data.y)) return ACCEL_ROTATION_0DEG;
		if (axis_is_mostly_negative(data.y)) return ACCEL_ROTATION_180DEG;
	}

	if (axis_is_mostly_positive(data.x)) return ACCEL_ROTATION_90DEG;

	if (axis_is_mostly_negative(data.x)) return ACCEL_ROTATION_270DEG;

	return ACCEL_ROTATION_NO_CHANGE;
}

void accel_stop_monitor(struct accel_monitor* monitor)
{
	monitor->monitoring_thread_should_exit = true;

	if (thrd_join(monitor->monitoring_thread, NULL) != thrd_success)
		fprintf(stderr,
		        "Can't join monitoring thread. The program may not exit "
		        "cleanly.\n");

	mtx_destroy(&monitor->current_data_lock);
	free(monitor);
}