Linux-Kernel-Internals

- Linux Kernel Internals: https://ankitkdev.com/blog/
- Char Driver: https://ankitkdev.com/blog/linux-kernel/device-driver/char-driver/
- Ioctl Interface: https://ankitkdev.com/blog/linux-kernel/device-driver/ioctl/
- Proc-Interface: https://ankitkdev.com/blog/linux-kernel/device-driver/proc/
- Completion-Variable: https://ankitkdev.com/blog/linux-kernel/concurrency/completion-variable/
- container_of(): https://ankitkdev.com/blog/linux-kernel/macros/container_of/
- Module Parameters: https://ankitkdev.com/blog/linux-kernel/macros/kernel-module/
- pr_fmt(): https://ankitkdev.com/blog/linux-kernel/macros/pr-family/
- Stringification: https://ankitkdev.com/blog/linux-kernel/macros/string/
- Debugging Macros: https://ankitkdev.com/blog/linux-kernel/macros/debug/
- Error Handling with Pointers: https://ankitkdev.com/blog/kernal-internals/error-handling/
- Kbuild Makefile: https://ankitkdev.com/blog/kernal-internals/kbuild/
- SLUB debug: https://ankitkdev.com/blog/kernel-debugging/debug-slub-memory/
- unsigned :\ 0 Bit-Fields in c: https://ankitkdev.com/blog/c/zero-width-bit-field/
- do { ... } while (0): https://ankitkdev.com/blog/c/do-while-loop/
- Error Handling: https://ankitkdev.com/blog/c/error-handling/
- C Memory Layout: https://ankitkdev.com/blog/c/c-memory-layout/
- Forward Declarations: https://ankitkdev.com/blog/c/forward-declaration-in-c/
- Return value by Macro: https://ankitkdev.com/blog/c/return-by-macro/
- Variadic Macro: https://ankitkdev.com/blog/c/variadic-macro/
- programming concepts: https://ankitkdev.com/blog/theory/
- Build & Install Linux Kernel for BBB: https://ankitkdev.com/blog/misc/build-linux-kernel-BBB/
- Configure U-boot for BBB: https://ankitkdev.com/blog/misc/configure-uboot-bbb/
- Install Ubuntu Server on Qemu: https://ankitkdev.com/blog/misc/install-ubuntu-server-on-qemu/
- Linux Kernel Mentorship Program: https://ankitkdev.com/blog/misc/linux-kernel-mentorship-program/


## Stringification

`include/linux/stringify.h` defines:

```c
#define __stringify_1(x...)    #x
#define __stringify(x...)      __stringify_1(x)
```

Both use `#` to turn an argument into a string literal. They differ only when the argument is a macro.

`#` stringifies tokens *before* expanding any macros in them. So `__stringify_1(x)` gives you the literal text you passed, macro name included, unexpanded.

`__stringify(x)` adds one layer of indirection. Since `x` isn't touched directly by `#` inside `__stringify`, the preprocessor expands `x` first when it's passed down to `__stringify_1`, which then stringifies the *expanded* result.

Example:

```c
#define KVERSION 6

pr_info("%s\n", __stringify_1(KVERSION));
// "KVERSION"

pr_info("%s\n", __stringify(KVERSION));
// "6"

char *hello = "world";

pr_info("%s\n", __stringify_1(hello));
// "hello"

pr_info("%s\n", __stringify(hello));
// "hello"

```

For a non-macro token: a variable name, a plain string, there's nothing to expand, so both macros produce the same output. 

> **Note**: The indirection only work when the argument is a `#define`.