Move debugfs, rootfs and procfs documentation to README

kernel_module/README.adoc

@@ -20,14 +20,11 @@
 ... link:dep2.c[]
 . Pseudo filesystems
 .. link:anonymous_inode.c[]
-.. link:debugfs.c[]
 .. link:ioctl.c[]
 .. link:mmap.c[]
 .. link:poll.c[]
-.. link:procfs.c[]
 .. link:seq_file.c[]
 .. link:seq_file_inode.c[]
-.. link:sysfs.c[]
 . Asynchronous
 .. link:irq.c[]
 .. link:kthread.c[]

kernel_module/character_device.c

@@ -1,3 +1,5 @@
+/* https://github.com/cirosantilli/linux-kernel-module-cheat#character-devices */
+
 #include <linux/fs.h> /* register_chrdev, unregister_chrdev */
 #include <linux/module.h>
 #include <linux/seq_file.h> /* seq_read, seq_lseek, single_release */

kernel_module/character_device_create.c

@@ -1,3 +1,5 @@
+/* https://github.com/cirosantilli/linux-kernel-module-cheat#automatically-create-character-device-file-on-insmod */
+
 #include <linux/cdev.h>
 #include <linux/device.h>
 #include <linux/fs.h> /* register_chrdev, unregister_chrdev */

kernel_module/debugfs.c

@@ -1,17 +1,4 @@
-/*
-Adapted from: https://github.com/chadversary/debugfs-tutorial/blob/47b3cf7ca47208c61ccb51b27aac6f9f932bfe0b/example1/debugfs_example1.c
-
-Usage:
-
-	/debugfs.sh
-
-Requires `CONFIG_DEBUG_FS=y`.
-
-Only the more basic fops can be implemented in debugfs, e.g. mmap is never called:
-
-- https://patchwork.kernel.org/patch/9252557/
-- https://github.com/torvalds/linux/blob/v4.9/fs/debugfs/file.c#L212
-*/
+/* https://github.com/cirosantilli/linux-kernel-module-cheat#debugfs */
 
 #include <linux/debugfs.h>
 #include <linux/kernel.h>

kernel_module/procfs.c

@@ -1,15 +1,4 @@
-/*
-Yet another fops entrypoint.
-
-https://stackoverflow.com/questions/8516021/proc-create-example-for-kernel-module
-
-	insmod /procfs.ko
-	cat /proc/lkmc_procfs
-
-Output:
-
-	abcd
-*/
+/* https://github.com/cirosantilli/linux-kernel-module-cheat#procfs */
 
 #include <linux/debugfs.h>
 #include <linux/module.h>

kernel_module/sysfs.c

@@ -1,24 +1,4 @@
-/*
-Adapted from: https://github.com/t3rm1n4l/kern-dev-tutorial/blob/1f036ef40fc4378f5c8d2842e55bcea7c6f8894a/05-sysfs/sysfs.c
-
-Vs procfs:
-
-- https://unix.stackexchange.com/questions/4884/what-is-the-difference-between-procfs-and-sysfs
-- https://stackoverflow.com/questions/37237835/how-to-attach-file-operations-to-sysfs-attribute-in-platform-driver
-
-This example shows how sysfs is more restricted, as it does not take a file_operations.
-
-So you basically can only do open, close, read, write, and lseek on sysfs files.
-
-It is kind of similar to a seq_file file_operations, except that write is also implemented.
-
-TODO: what are those kobject structs? Make a more complex example that shows what they can do.
-
-- https://www.kernel.org/doc/Documentation/kobject.txt
-- https://www.quora.com/What-are-kernel-objects-Kobj
-- http://www.makelinux.net/ldd3/chp-14-sect-1
-- https://www.win.tue.nl/~aeb/linux/lk/lk-13.html
-*/
+/* https://github.com/cirosantilli/linux-kernel-module-cheat#sysfs */
 
 #include <linux/init.h>
 #include <linux/kobject.h>