113 lines
3 KiB
C
113 lines
3 KiB
C
#include "linux/fs.h"
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#include "linux/types.h"
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#include <linux/gpio/consumer.h>
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#include <linux/init.h>
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#include <linux/kernel.h>
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#include <linux/module.h>
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/*
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* Last compiled with Linux 6.14.5-300.fc42.x86_64
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*/
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/* Meta Info */
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MODULE_DESCRIPTION("Chardev kernel module.");
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MODULE_VERSION("0.0.1");
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MODULE_AUTHOR("Imbus");
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MODULE_LICENSE("GPL");
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// Since were dynamically assigned a major device number, we will store it here
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static int major;
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static char text[64];
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// Regular forward decls
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static ssize_t my_read(struct file *f, char __user *u, size_t l, loff_t *o);
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static ssize_t my_write(struct file *, const char __user *, size_t, loff_t *);
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static int my_open(struct inode *, struct file *);
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static int my_release(struct inode *, struct file *);
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// See: https://elixir.bootlin.com/linux/v6.14.5/source/include/linux/fs.h#L2131
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static struct file_operations fops = {
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.read = my_read, .write = my_write, .open = my_open, .release = my_release};
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static ssize_t my_write(struct file *filp, const char __user *user_buf,
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size_t len, loff_t *off) {
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printk(KERN_INFO "hello_cdev - Write is called by %s...\n", current->comm);
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int not_copied, delta,
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to_copy = (len + *off) < sizeof(text) ? len : (sizeof(text) - *off);
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if (*off >= sizeof(text))
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return 0;
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not_copied = copy_from_user(text, user_buf, to_copy);
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delta = to_copy - not_copied;
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if (not_copied)
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pr_warn("hello_cdev - Could only copy %d bytes\n", delta);
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*off = delta;
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return delta;
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}
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static ssize_t my_read(struct file *filp, char __user *user_buf, size_t len,
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loff_t *off) {
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printk(KERN_INFO "hello_cdev - Read is called\n");
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int not_copied, delta,
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to_copy = (len + *off) < sizeof(text) ? len : (sizeof(text) - *off);
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if (*off >= sizeof(text))
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return 0;
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not_copied = copy_to_user(user_buf, text, to_copy);
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delta = to_copy - not_copied;
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if (not_copied)
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pr_warn("hello_cdev - Could only copy %d bytes\n", delta);
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*off = delta;
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return delta;
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}
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static int my_open(struct inode *inode, struct file *filp) {
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pr_info("hello-cdev - Major %d, Minor %d\n", imajor(inode), iminor(inode));
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pr_info("hello-cdev - filp->f_pos: %lld\n", filp->f_pos);
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pr_info("hello-cdev - filp->f_mode: 0x%x\n", filp->f_mode);
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pr_info("hello-cdev - filp->f_flags: 0x%x\n", filp->f_flags);
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return 0;
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}
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static int my_release(struct inode *inode, struct file *filp) {
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pr_info("hello-cdev - Closed \n");
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return 0;
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}
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/**
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* @brief Called on load
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*/
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static int __init demo_mod_init(void) {
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major = register_chrdev(0, "hello_cdev", &fops);
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if (major < 0) {
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printk(KERN_INFO "hello_cdev - Error registering chrdev\n");
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return major;
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}
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printk(KERN_INFO "hello_cdev - Major nbr %d loaded successfully...", major);
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return 0;
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}
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/**
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* @brief Called on unload
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*/
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static void __exit demo_mod_exit(void) {
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unregister_chrdev(major, "hello_cdev");
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printk(KERN_INFO "hello_cdev - unloaded successfully...");
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}
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module_init(demo_mod_init);
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module_exit(demo_mod_exit);
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