TASK04: Create simple GPIO Linux kernel driver

.gitignore

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+# Prerequisites
+*.d
+
+# Object files
+*.o
+*.ko
+*.obj
+*.elf
+
+# Linker output
+*.ilk
+*.map
+*.exp
+
+# Precompiled Headers
+*.gch
+*.pch
+
+# Libraries
+*.lib
+*.a
+*.la
+*.lo
+
+# Shared objects (inc. Windows DLLs)
+*.dll
+*.so
+*.so.*
+*.dylib
+
+# Executables
+*.exe
+*.out
+*.app
+*.i*86
+*.x86_64
+*.hex
+
+# Debug files
+*.dSYM/
+*.su
+*.idb
+*.pdb
+
+# Kernel Module Compile Results
+*.mod*
+*.cmd
+.tmp_versions/
+modules.order
+Module.symvers
+Mkfile.old
+dkms.conf

Makefile

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+
+CF = clang-format-12 -i
+
+.PHONY: format check-format check-arg
+
+check-arg:
+	@if test "$(DIR)" = "" ; then \
+		echo DIR not set; \
+		echo Use:;\
+		echo make cmd DIR=...;\
+		echo ;\
+		exit 1; \
+	fi
+
+format: check-arg
+	@echo format SRC
+	$(CF) $(DIR)/*.[ch]
+
+check-format: check-arg
+	@echo "\n\e[32m*** Check format of source code ***\e[0m\n"
+	@utils/checkpatch.pl --no-tree -f $(DIR)/*.[ch]

Task04_simple_kernel_drive/Makefile

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+obj-m += encoder_driver.o
+
+KDIR = /lib/modules/$(shell uname -r)/build
+
+all:
+	make -C $(KDIR)  M=$(shell pwd) modules
+
+clean:
+	make -C $(KDIR)  M=$(shell pwd) clean
+

Task04_simple_kernel_drive/ReadMe.md

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+# Simple encoder Linux Kernel Driver
+
+Build command:
+
+	sudo make
+
+For install driver
+
+	sudo insmod encoder_driver.ko
+
+For clean build:
+
+	sudo make clean
+
+For check and control of results:
+
+	dmesg -wH
+
+For read of encoder value:
+
+	watch -n 0.1 cat /sys/module/encoder_driver/parameters/encoder_value 
+
+For remove driver:
+
+	rmmod encoder_driver
+
+
+## References:
+
+https://tldp.org/LDP/lkmpg/2.6/html/c119.html
+
+https://sysprog21.github.io/lkmpg/#hello-world
+
+https://embetronicx.com/tutorials/linux/device-drivers/gpio-driver-basic-using-raspberry-pi/
+
+https://embetronicx.com/tutorials/linux/device-drivers/gpio-linux-device-driver-using-raspberry-pi/
+

Task04_simple_kernel_drive/encoder_driver.c

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+// SPDX-License-Identifier: GPL-2.0+
+
+/*
+ * encoder_driver.c - simple encoder driver for linux kernel
+ */
+
+#include <linux/gpio.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+
+// Pins with encoder
+#define GPIO_PIN_A 7
+#define GPIO_PIN_B 8
+
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Yurii.Bezkor");
+MODULE_DESCRIPTION("Encoder driver");
+MODULE_VERSION("0.2");
+
+int encoder_value; // value encoder
+
+unsigned int gpio_irq; // IRQ number
+
+// Register params
+module_param(encoder_value, int, 0664);
+
+/*
+ * IRQ handler
+ */
+static irqreturn_t gpio_irq_handler(int irq, void *dev_id)
+{
+	static unsigned long flags;
+
+	local_irq_save(flags);
+
+	if (gpio_get_value(GPIO_PIN_B))
+		encoder_value++;
+	else
+		encoder_value--;
+
+	pr_info("encoder_value = %d\n", encoder_value);
+
+	local_irq_restore(flags);
+
+	return IRQ_HANDLED;
+}
+
+/*
+ * Module init function
+ */
+static int __init encoder_init(void)
+{
+	// Error code variable
+	int error_code;
+
+	// Check is GPIO valid
+	if (false == gpio_is_valid(GPIO_PIN_A)) {
+		pr_err("GPIO_PIN_A = %d not valid\n", GPIO_PIN_A);
+		return -EINVAL;
+	}
+	pr_info("GPIO_PIN_A = %d is valid\n", GPIO_PIN_A);
+
+	if (false == gpio_is_valid(GPIO_PIN_B)) {
+		pr_err("GPIO_PIN_B = %d not valid\n", GPIO_PIN_B);
+		return -EINVAL;
+	}
+	pr_info("GPIO_PIN_B = %d is valid\n", GPIO_PIN_B);
+
+	// Try GPIO request
+	error_code = gpio_request(GPIO_PIN_A, "Pin A");
+	if (error_code) {
+		pr_err("GPIO_PIN_A request error\n");
+		return error_code;
+	}
+	pr_info("GPIO_PIN_A = %d request is OK\n", GPIO_PIN_A);
+
+	error_code = gpio_request(GPIO_PIN_B, "Pin B");
+	if (error_code) {
+		pr_err("GPIO_PIN_B request error\n");
+		return error_code;
+	}
+	pr_info("GPIO_PIN_B = %d request is OK\n", GPIO_PIN_B);
+
+	// Config pins as input
+	gpio_direction_input(GPIO_PIN_A);
+	pr_info("Config A = %d\n", GPIO_PIN_A);
+	gpio_direction_input(GPIO_PIN_B);
+	pr_info("Config B = %d\n", GPIO_PIN_B);
+
+	// Config pin A as IRQ pin
+	gpio_irq = gpio_to_irq(GPIO_PIN_A);
+	pr_info("Config IRQ = %d\n", gpio_irq);
+
+	// Try register IRQ
+	error_code = request_irq(gpio_irq, (void *)gpio_irq_handler,
+				 IRQF_TRIGGER_FALLING, "encoder_device", NULL);
+	if (error_code) {
+		pr_info("Error IRQ request\n");
+		return error_code;
+	}
+	pr_info("IRQ request is OK\n");
+
+	// Init default encoder value
+	encoder_value = 0;
+	pr_info("encoder_value = %d\n", encoder_value);
+
+	pr_info("Encoder Kernel Module Inserted Successfully...\n");
+	return 0;
+}
+
+/*
+ * Module Exit function
+ */
+static void __exit encoder_exit(void)
+{
+	free_irq(gpio_irq, NULL);
+	gpio_free(GPIO_PIN_A);
+	gpio_free(GPIO_PIN_B);
+	pr_info("Encoder Kernel Module Removed Successfully...\n");
+}
+
+module_init(encoder_init);
+module_exit(encoder_exit);
+
+/*
+ * NOTE:
+ * Init procedure of GPIO
+ * gpio_is_valid -> gpio_request -> gpio_direction_input
+ * can be replaced by a cleaner and more correct call
+ * gpio_request_one or gpio_request_array
+ */