init

.gitignore

@@ -0,0 +1,174 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# NOTE! Don't add files that are generated in specific
+# subdirectories here. Add them in the ".gitignore" file
+# in that subdirectory instead.
+#
+# NOTE! Please use 'git ls-files -i -c --exclude-per-directory=.gitignore'
+# command after changing this file, to see if there are
+# any tracked files which get ignored after the change.
+#
+# Normal rules (sorted alphabetically)
+#
+.*
+*.a
+*.asn1.[ch]
+*.bin
+*.bz2
+*.c.[012]*.*
+*.cover
+*.dt.yaml
+*.dtb
+*.dtbo
+*.dtb.S
+*.dtbo.S
+*.dwo
+*.elf
+*.gcno
+*.gz
+*.i
+*.ko
+*.lex.c
+*.ll
+*.lst
+*.lz4
+*.lzma
+*.lzo
+*.mbx
+*.mod
+*.mod.c
+*.o
+*.o.*
+*.patch
+*.rmeta
+*.rpm
+*.rsi
+*.s
+*.so
+*.so.dbg
+*.su
+*.symtypes
+*.symversions
+*.tab.[ch]
+*.tar
+*.usyms
+*.xz
+*.zst
+Module.symvers
+modules.order
+
+#
+# Top-level generic files
+#
+/linux
+/modules-only.symvers
+/vmlinux
+/vmlinux.32
+/vmlinux.map
+/vmlinux.symvers
+/vmlinux-gdb.py
+/vmlinuz
+/System.map
+/Module.markers
+/modules.builtin
+/modules.builtin.modinfo
+/modules.nsdeps
+
+#
+# RPM spec file (make rpm-pkg)
+#
+/*.spec
+
+#
+# Debian directory (make deb-pkg)
+#
+/debian/
+
+#
+# Snap directory (make snap-pkg)
+#
+/snap/
+
+#
+# tar directory (make tar*-pkg)
+#
+/tar-install/
+
+#
+# We don't want to ignore the following even if they are dot-files
+#
+!.clang-format
+!.cocciconfig
+!.get_maintainer.ignore
+!.gitattributes
+!.gitignore
+!.mailmap
+!.rustfmt.toml
+
+#
+# Generated include files
+#
+/include/config/
+/include/generated/
+/include/ksym/
+/arch/*/include/generated/
+
+# stgit generated dirs
+patches-*
+
+# quilt's files
+patches
+series
+
+# ctags files
+tags
+TAGS
+
+# cscope files
+cscope.*
+ncscope.*
+
+# gnu global files
+GPATH
+GRTAGS
+GSYMS
+GTAGS
+
+# id-utils files
+ID
+
+*.orig
+*~
+\#*#
+
+#
+# Leavings from module signing
+#
+extra_certificates
+signing_key.pem
+signing_key.priv
+signing_key.x509
+x509.genkey
+
+# Kconfig presets
+/all.config
+/alldef.config
+/allmod.config
+/allno.config
+/allrandom.config
+/allyes.config
+
+# Kconfig savedefconfig output
+/defconfig
+
+# Kdevelop4
+*.kdev4
+
+# Clang's compilation database file
+/compile_commands.json
+
+# Documentation toolchain
+sphinx_*/
+
+# Rust analyzer configuration
+/rust-project.json

Makefile

@@ -0,0 +1,10 @@
+KDIR=/usr/src/kernels/$(shell uname -r)
+
+obj-m += demo.o
+
+all:
+	make -C $(KDIR) M=$(shell pwd) modules
+
+clean:
+	make -C $(KDIR) M=$(shell pwd) clean
+

demo.c

@@ -0,0 +1,86 @@
+#include <linux/module.h>
+#include <linux/fs.h>
+#include <linux/cdev.h>
+
+MODULE_LICENSE("GPL v2");
+
+static ssize_t demo_read(struct file *filp, char __user *buff, size_t size, loff_t *pos)
+{
+	printk("%s %d\n", __func__, __LINE__);
+	return size;
+}
+
+static ssize_t demo_write(struct file *filp, const char __user *buff, size_t size, loff_t *pos)
+{
+	printk("%s %d\n", __func__, __LINE__);
+	return size;
+}
+
+static int demo_open(struct inode *inode, struct file *filp)
+{
+	printk("%s %d\n", __func__, __LINE__);
+	return 0;
+}
+
+static int demo_release(struct inode *inode, struct file *filp)
+{
+	printk("%s %d\n", __func__, __LINE__);
+	return 0;
+}
+
+struct file_operations demo_fops = {
+	.owner      = THIS_MODULE,
+	.read       = demo_read,
+	.write      = demo_write,
+	.open       = demo_open,
+	.release    = demo_release,
+};
+
+static dev_t dev;
+static struct cdev *cdev;
+
+int demo_init(void)
+{
+	int rc;
+
+	rc = alloc_chrdev_region(&dev, 0, 1, "demo");
+	if (rc) {
+		printk("failed to alloc chrdev number\n");
+		return rc;
+	}
+
+	cdev = cdev_alloc();
+	if (!cdev) {
+		printk("failed to alloc cdev\n");
+		rc = -ENOMEM;
+		goto out_unregister_chrdev;
+	}
+
+	cdev->owner = THIS_MODULE;
+	cdev_init(cdev, &demo_fops);
+
+	rc = cdev_add(cdev, dev, 1);
+	if (rc) {
+		printk("failed to add char device\n");
+		goto out_free_cdev;
+	}
+
+	return 0;
+
+out_free_cdev:
+	kobject_put(&cdev->kobj);	
+
+out_unregister_chrdev:
+	unregister_chrdev_region(dev, 1);
+
+	return rc;
+}
+
+void demo_exit(void)
+{
+	cdev_del(cdev);
+	unregister_chrdev_region(dev, 1);
+}
+
+module_init(demo_init);
+module_exit(demo_exit);

mknod.sh

@@ -0,0 +1,6 @@
+#!/bin/sh
+
+major=$(cat /proc/devices  | grep demo)
+
+mknode /dev/demo c $major 0
+