Add null GPIO pin (#6611)

esphome/components/cst226/touchscreen/cst226_touchscreen.cpp

@@ -5,7 +5,6 @@ namespace cst226 {
 
 void CST226Touchscreen::setup() {
   esph_log_config(TAG, "Setting up CST226 Touchscreen...");
-  if (this->reset_pin_ != nullptr) {
   this->reset_pin_->setup();
   this->reset_pin_->digital_write(true);
   delay(5);
@@ -13,9 +12,6 @@ void CST226Touchscreen::setup() {
   delay(5);
   this->reset_pin_->digital_write(true);
   this->set_timeout(30, [this] { this->continue_setup_(); });
-  } else {
-    this->continue_setup_();
-  }
 }
 
 void CST226Touchscreen::update_touches() {

esphome/components/cst226/touchscreen/cst226_touchscreen.h

@@ -35,7 +35,7 @@ class CST226Touchscreen : public touchscreen::Touchscreen, public i2c::I2CDevice
   void continue_setup_();
 
   InternalGPIOPin *interrupt_pin_{};
-  GPIOPin *reset_pin_{};
+  GPIOPin *reset_pin_{NULL_PIN};
   uint8_t chip_id_{};
   bool setup_complete_{};
 };

esphome/core/gpio.h

@@ -62,6 +62,24 @@ class GPIOPin {
   virtual bool is_internal() { return false; }
 };
 
+/**
+ * A pin to replace those that don't exist.
+ */
+class NullPin : public GPIOPin {
+ public:
+  void setup() override {}
+
+  void pin_mode(gpio::Flags _) override {}
+
+  bool digital_read() override { return false; }
+
+  void digital_write(bool _) override {}
+
+  std::string dump_summary() const override { return {"Not used"}; }
+};
+
+static GPIOPin *const NULL_PIN = new NullPin();
+
 /// Copy of GPIOPin that is safe to use from ISRs (with no virtual functions)
 class ISRInternalGPIOPin {
  public: