io_timer: reserve pins & timers on first use

This allows modules to do a first-come-first-serve pin/timer reservation
on bootup.
E.g. camera trigger reserves any of the pins, and then PWM/DShot output
will just use the rest of the available pins.

src/drivers/camera_trigger/interfaces/src/gpio.cpp

@@ -51,15 +51,35 @@ CameraInterfaceGPIO::CameraInterfaceGPIO()
 	setup();
 }
 
+CameraInterfaceGPIO::~CameraInterfaceGPIO()
+{
+	unsigned channel = 0;
+
+	while (_allocated_channels != 0) {
+		if (((1 << channel) & _allocated_channels)) {
+			io_timer_unallocate_channel(channel);
+			_allocated_channels &= ~(1u << channel);
+		}
+
+		++channel;
+	}
+}
+
 void CameraInterfaceGPIO::setup()
 {
+	_allocated_channels = 0;
+
 	for (unsigned i = 0, t = 0; i < arraySize(_pins); i++) {
 		// Pin range is from 0 to num_gpios - 1
 		if (_pins[i] >= 0 && t < (int)arraySize(_triggers)) {
 			uint32_t gpio = io_timer_channel_get_gpio_output(_pins[i]);
-			_triggers[t++] = gpio;
-			px4_arch_configgpio(gpio);
-			px4_arch_gpiowrite(gpio, false ^ _trigger_invert);
+
+			if (io_timer_allocate_channel(_pins[i], IOTimerChanMode_Trigger) == 0) {
+				_allocated_channels |= 1 << _pins[i];
+				_triggers[t++] = gpio;
+				px4_arch_configgpio(gpio);
+				px4_arch_gpiowrite(gpio, false ^ _trigger_invert);
+			}
 		}
 	}
 }

src/drivers/camera_trigger/interfaces/src/gpio.h

@@ -49,7 +49,7 @@ class CameraInterfaceGPIO : public CameraInterface
 {
 public:
 	CameraInterfaceGPIO();
-	virtual ~CameraInterfaceGPIO() = default;
+	virtual ~CameraInterfaceGPIO();
 
 	void trigger(bool trigger_on_true);
 
@@ -65,6 +65,7 @@ private:
 	bool _trigger_invert{false};
 
 	uint32_t _triggers[num_gpios] {};
+	uint32_t _allocated_channels{0};
 };
 
 #endif /* ifdef __PX4_NUTTX */

src/drivers/camera_trigger/interfaces/src/pwm.cpp

@@ -68,7 +68,22 @@ void CameraInterfacePWM::setup()
 	}
 
 	// Initialize and arm channels
-	up_pwm_trigger_init(pin_bitmask);
+	int ret = up_pwm_trigger_init(pin_bitmask);
+
+	if (ret < 0) {
+		PX4_ERR("up_pwm_trigger_init failed (%i)", ret);
+		pin_bitmask = 0;
+
+	} else {
+		pin_bitmask = ret;
+	}
+
+	// Clear pins that could not be initialized
+	for (unsigned i = 0; i < arraySize(_pins); i++) {
+		if (_pins[i] >= 0 && ((1 << _pins[i]) & pin_bitmask) == 0) {
+			_pins[i] = -1;
+		}
+	}
 
 	// Set neutral pulsewidths
 	for (unsigned i = 0; i < arraySize(_pins); i++) {

src/drivers/camera_trigger/interfaces/src/seagull_map2.cpp

@@ -69,7 +69,12 @@ void CameraInterfaceSeagull::setup()
 
 			// Initialize the interface
 			uint32_t pin_bitmask = (1 << _pins[i + 1]) | (1 << _pins[i]);
-			up_pwm_trigger_init(pin_bitmask);
+			int ret = up_pwm_trigger_init(pin_bitmask);
+
+			if (ret != (int)pin_bitmask) {
+				PX4_WARN("up_pwm_trigger_init failed (%i)", ret);
+				continue;
+			}
 
 			// Set both interface pins to disarmed
 			int ret1 = up_pwm_trigger_set(_pins[i + 1], PWM_CAMERA_DISARMED);