unit test for GPIO race condition on Linux

Related to ArduPilot#25007

libraries/AP_HAL/GPIO.h

@@ -49,6 +49,7 @@ class AP_HAL::GPIO {
     GPIO() {}
     virtual void    init() = 0;
     virtual void    pinMode(uint8_t pin, uint8_t output) = 0;
+    virtual void    pinModeValidate(uint8_t pin, uint8_t output) = 0;
 
     // optional interface on some boards
     virtual void    pinMode(uint8_t pin, uint8_t output, uint8_t alt) {};

libraries/AP_HAL_Linux/GPIO_RPI.cpp

@@ -34,6 +34,7 @@ const char* GPIO_RPI::_system_memory_device_path = "/dev/mem";
 
 GPIO_RPI::GPIO_RPI()
 {
+fprintf(stderr,"%s:%i\n",__func__,__LINE__);
 }
 
 void GPIO_RPI::set_gpio_mode_alt(int pin, int alternative)
@@ -93,6 +94,21 @@ void GPIO_RPI::set_gpio_mode_out(int pin)
     _gpio[pin / pins_per_register] = register_value | mask_with_bit;
 }
 
+uint8_t GPIO_RPI::get_gpio_mode(int pin)
+{
+    // Each register can contain 10 pins
+    const uint8_t pins_per_register = 10;
+    // Calculates the position of the 3 bit mask in the 32 bits register
+    const uint8_t tree_bits_position_in_register = (pin%pins_per_register)*3;
+    // Create a mask to enable the bit that sets output functionality
+    // 0b00'000'000'000'000'000'000'001'000'000'000 enables output for the 4th pin
+    const uint32_t mask_with_bit = 0b001 << tree_bits_position_in_register;
+    // Clear all bits in our position and apply our mask with alt values
+    const uint32_t register_value = _gpio[pin / pins_per_register];
+    return !!(register_value & mask_with_bit);
+}
+
+
 void GPIO_RPI::set_gpio_high(int pin)
 {
     // Calculate index of the array for the register GPSET0 (0x7E20'001C)
@@ -160,6 +176,7 @@ void GPIO_RPI::closeMemoryDevice()
 
 void GPIO_RPI::init()
 {
+    fprintf(stderr,"%s:%i\n",__func__,__LINE__);
     const LINUX_BOARD_TYPE rpi_version = UtilRPI::from(hal.util)->detect_linux_board_type();
 
     GPIO_RPI::Address peripheral_base;
@@ -200,6 +217,13 @@ void GPIO_RPI::pinMode(uint8_t pin, uint8_t output)
     }
 }
 
+void GPIO_RPI::pinModeValidate(uint8_t pin, uint8_t output)
+{
+    if(get_gpio_mode(pin) != output) {
+        AP_HAL::panic("GPIO mode validation failed!");
+    }
+}
+
 void GPIO_RPI::pinMode(uint8_t pin, uint8_t output, uint8_t alt)
 {
     if (output == HAL_GPIO_INPUT) {

libraries/AP_HAL_Linux/GPIO_RPI.h

@@ -28,6 +28,7 @@ class GPIO_RPI : public AP_HAL::GPIO {
     GPIO_RPI();
     void    init() override;
     void    pinMode(uint8_t pin, uint8_t output) override;
+    void    pinModeValidate(uint8_t pin, uint8_t output) override;
     void    pinMode(uint8_t pin, uint8_t output, uint8_t alt) override;
     uint8_t read(uint8_t pin) override;
     void    write(uint8_t pin, uint8_t value) override;
@@ -85,6 +86,15 @@ class GPIO_RPI : public AP_HAL::GPIO {
      */
     uint32_t get_address(GPIO_RPI::Address address, GPIO_RPI::PeripheralOffset offset) const;
 
+    /**
+     * @brief Get a specific GPIO's mode
+     * Check Linux::GPIO_RPI::set_gpio_mode_alt for more information.
+     *
+     * @param pin
+     * @return int mode
+     */
+    uint8_t get_gpio_mode(int pin);
+
     /**
      * @brief Change functionality of GPIO Function Select Registers (GPFSELn) to any alternative function.
      * Each GPIO pin is mapped to 3 bits inside a 32 bits register, E.g:

libraries/AP_HAL_Linux/tests/test_gpio_dir_race.cpp

@@ -0,0 +1,56 @@
+/*
+ * Copyright (C) 2016  Intel Corporation. All rights reserved.
+ *
+ * This file is free software: you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This file is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ * See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#include <AP_gtest.h>
+
+#include <pthread.h>
+#include <unistd.h>
+
+#include <AP_HAL/AP_HAL.h>
+#include <AP_HAL_Linux/GPIO.h>
+
+using namespace Linux;
+
+const AP_HAL::HAL &hal = AP_HAL::get_HAL();
+
+#define TEST_PIN 12
+
+class TestGpioMode1 {
+public:
+    TestGpioMode1() { }
+
+    bool run() {
+        hal.gpio->pinMode(TEST_PIN, HAL_GPIO_INPUT);
+        hal.gpio->pinModeValidate(TEST_PIN, HAL_GPIO_INPUT);
+        hal.gpio->pinMode(TEST_PIN, HAL_GPIO_OUTPUT);
+        hal.gpio->pinModeValidate(TEST_PIN, HAL_GPIO_OUTPUT);
+        return true;
+    }
+
+protected:
+};
+
+TEST(LinuxGpio, override_run)
+{
+    TestGpioMode1 gpio;
+    fprintf(stderr,"Initializing HAL\n");
+    hal.gpio->init();
+    fprintf(stderr,"Launching test run\n");
+    while (gpio.run()) {
+    }
+}
+
+AP_GTEST_MAIN()

libraries/AP_HAL_Linux/tests/test_gpio_dir_racer.sh

@@ -0,0 +1,6 @@
+UNRELATED_PIN=13
+while :
+do
+    sudo raspi-gpio set ${UNRELATED_PIN} ip
+    sudo raspi-gpio set ${UNRELATED_PIN} op
+done