148 lines
3.5 KiB
C
148 lines
3.5 KiB
C
#include <linux/module.h>
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#include <linux/init.h>
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#include <linux/mod_devicetable.h>
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#include <linux/property.h>
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#include <linux/platform_device.h>
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#include <linux/of_device.h>
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#include <linux/gpio/consumer.h>
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#include <linux/proc_fs.h>
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/* Meta Information */
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("Johannes 4 GNU/Linux");
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MODULE_DESCRIPTION("A simple LKM to parse the device tree for a specific device and its properties");
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/* Declate the probe and remove functions */
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static int dt_probe(struct platform_device *pdev);
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static void dt_remove(struct platform_device *pdev);
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static struct of_device_id my_driver_ids[] = {
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{
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.compatible = "brightlight,mydev",
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}, { /* sentinel */ }
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};
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MODULE_DEVICE_TABLE(of, my_driver_ids);
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static struct platform_driver my_driver = {
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.probe = dt_probe,
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.remove = dt_remove,
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.driver = {
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.name = "my_device_driver",
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.of_match_table = my_driver_ids,
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},
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};
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/* GPIO variable */
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static struct gpio_desc *my_led = NULL;
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static struct proc_dir_entry *proc_file;
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/**
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* @brief Write data to buffer
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*/
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static ssize_t my_write(struct file *File, const char *user_buffer, size_t count, loff_t *offs) {
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switch (user_buffer[0]) {
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case '0':
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case '1':
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gpiod_set_value(my_led, user_buffer[0] - '0');
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default:
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break;
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}
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return count;
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}
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static struct proc_ops fops = {
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.proc_write = my_write,
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};
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/**
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* @brief This function is called on loading the driver
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*/
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static int dt_probe(struct platform_device *pdev) {
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struct device *dev = &pdev->dev;
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const char *label;
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int my_value, ret;
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printk("dt_gpio - Now I am in the probe function!\n");
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/* Check for device properties */
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if(!device_property_present(dev, "label")) {
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printk("dt_gpio - Error! Device property 'label' not found!\n");
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return -1;
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}
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if(!device_property_present(dev, "my_value")) {
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printk("dt_gpio - Error! Device property 'my_value' not found!\n");
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return -1;
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}
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if(!device_property_present(dev, "green-led-gpio")) {
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printk("dt_gpio - Error! Device property 'green-led-gpio' not found!\n");
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return -1;
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}
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/* Read device properties */
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ret = device_property_read_string(dev, "label", &label);
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if(ret) {
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printk("dt_gpio - Error! Could not read 'label'\n");
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return -1;
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}
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printk("dt_gpio - label: %s\n", label);
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ret = device_property_read_u32(dev, "my_value", &my_value);
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if(ret) {
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printk("dt_gpio - Error! Could not read 'my_value'\n");
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return -1;
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}
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printk("dt_gpio - my_value: %d\n", my_value);
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/* Init GPIO */
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my_led = gpiod_get(dev, "green-led", GPIOD_OUT_LOW);
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if(IS_ERR(my_led)) {
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printk("dt_gpio - Error! Could not setup the GPIO\n");
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return -1 * IS_ERR(my_led);
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}
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/* Creating procfs file */
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proc_file = proc_create("my-led", 0666, NULL, &fops);
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if(proc_file == NULL) {
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printk("procfs_test - Error creating /proc/my-led\n");
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gpiod_put(my_led);
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return -ENOMEM;
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}
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return 0;
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}
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/**
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* @brief This function is called on unloading the driver
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*/
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static void dt_remove(struct platform_device *pdev) {
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printk("dt_gpio - Now I am in the remove function\n");
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gpiod_put(my_led);
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proc_remove(proc_file);
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}
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/**
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* @brief This function is called, when the module is loaded into the kernel
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*/
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static int __init my_init(void) {
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printk("dt_gpio - Loading the driver...\n");
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if(platform_driver_register(&my_driver)) {
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printk("dt_gpio - Error! Could not load driver\n");
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return -1;
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}
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return 0;
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}
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/**
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* @brief This function is called, when the module is removed from the kernel
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*/
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static void __exit my_exit(void) {
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printk("dt_gpio - Unload driver");
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platform_driver_unregister(&my_driver);
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}
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module_init(my_init);
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module_exit(my_exit);
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