From 62bb8aeeda0e27a5ceec3407697d400fda31004b Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@home-assistant.io>
Date: Sat, 4 Apr 2026 22:11:04 -1000
Subject: [PATCH] [pcf8574][pca9554] Disable loop when all pins are outputs

When an expander has only output pins configured, loop() was still
running every iteration to invalidate the read cache. Since no
digital_read() calls will ever be made, this work is wasted.

Now disable_loop() is called unconditionally in setup(). For polling
mode, loop is re-enabled only when pin_mode() registers an input pin.
For interrupt-driven mode, behavior is unchanged as the ISR already
manages loop enablement.
---
 esphome/components/pca9554/pca9554.cpp | 11 +++++++++--
 esphome/components/pcf8574/pcf8574.cpp | 11 +++++++++--
 2 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/esphome/components/pca9554/pca9554.cpp b/esphome/components/pca9554/pca9554.cpp
index 9b300eaac2..ac4f119dfe 100644
--- a/esphome/components/pca9554/pca9554.cpp
+++ b/esphome/components/pca9554/pca9554.cpp
@@ -40,9 +40,11 @@ void PCA9554Component::setup() {
     this->interrupt_pin_->attach_interrupt(&PCA9554Component::gpio_intr, this, gpio::INTERRUPT_FALLING_EDGE);
     // Don't invalidate cache on read — only invalidate when interrupt fires
     this->set_invalidate_on_read_(false);
-    // With interrupt pin, only run loop when interrupt fires
-    this->disable_loop();
   }
+  // Disable loop until an input pin is configured via pin_mode()
+  // For interrupt-driven mode, loop is re-enabled by the ISR
+  // For polling mode, loop is re-enabled when pin_mode() registers an input pin
+  this->disable_loop();
 }
 void IRAM_ATTR PCA9554Component::gpio_intr(PCA9554Component *arg) { arg->enable_loop_soon_any_context(); }
 void PCA9554Component::loop() {
@@ -89,6 +91,11 @@ void PCA9554Component::pin_mode(uint8_t pin, gpio::Flags flags) {
   if (flags == gpio::FLAG_INPUT) {
     // Clear mode mask bit
     this->config_mask_ &= ~(1 << pin);
+    // Enable polling loop for input pins (not needed for interrupt-driven mode
+    // where the ISR handles re-enabling loop)
+    if (this->interrupt_pin_ == nullptr) {
+      this->enable_loop();
+    }
   } else if (flags == gpio::FLAG_OUTPUT) {
     // Set mode mask bit
     this->config_mask_ |= 1 << pin;
diff --git a/esphome/components/pcf8574/pcf8574.cpp b/esphome/components/pcf8574/pcf8574.cpp
index 1eeef663b0..bf4a9442a2 100644
--- a/esphome/components/pcf8574/pcf8574.cpp
+++ b/esphome/components/pcf8574/pcf8574.cpp
@@ -21,9 +21,11 @@ void PCF8574Component::setup() {
     this->interrupt_pin_->attach_interrupt(&PCF8574Component::gpio_intr, this, gpio::INTERRUPT_FALLING_EDGE);
     // Don't invalidate cache on read — only invalidate when interrupt fires
     this->set_invalidate_on_read_(false);
-    // With interrupt pin, only run loop when interrupt fires
-    this->disable_loop();
   }
+  // Disable loop until an input pin is configured via pin_mode()
+  // For interrupt-driven mode, loop is re-enabled by the ISR
+  // For polling mode, loop is re-enabled when pin_mode() registers an input pin
+  this->disable_loop();
 }
 void IRAM_ATTR PCF8574Component::gpio_intr(PCF8574Component *arg) { arg->enable_loop_soon_any_context(); }
 void PCF8574Component::loop() {
@@ -66,6 +68,11 @@ void PCF8574Component::pin_mode(uint8_t pin, gpio::Flags flags) {
     this->mode_mask_ &= ~(1 << pin);
     // Write GPIO to enable input mode
     this->write_gpio_();
+    // Enable polling loop for input pins (not needed for interrupt-driven mode
+    // where the ISR handles re-enabling loop)
+    if (this->interrupt_pin_ == nullptr) {
+      this->enable_loop();
+    }
   } else if (flags == gpio::FLAG_OUTPUT) {
     // Set mode mask bit
     this->mode_mask_ |= 1 << pin;