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/


### The Structural Wrapper: `do { ... } while (0)`

Standard macro design pattern. Forces the macro to behave like a single C statement, so it can't break syntax when used inside an `if/else` without braces.

```c
#define LOG_DEBUG(msg) do { \
    printk(KERN_DEBUG msg); \
    debug_count++; \
} while (0)

if (tmp)
    LOG_DEBUG("checking condition\n");
else
    do_something();
```

> Two statements is where this trick stops being a nice-to-have and becomes necessary. Without the wrapper:
>
> ```c
> #define LOG_DEBUG(msg) printk(KERN_DEBUG msg); debug_count++;
> ```
>
> expands the `if` branch into two separate statements, only the first one belongs to the `if`, the second runs unconditionally regardless of `tmp`. Wrap braces `{ }` around it instead and you hit the classic dangling-`;` problem: the trailing `;` after the macro call becomes an empty statement, and the `else` ends up with no matching `if`.

The `do { } while (0)` fixes both: it groups any number of statements into one block, and swallows the semicolon you put after the macro call. `while (0)` never loops, so the compiler optimizes it away, zero runtime cost.