OS Kernel

Writing an OS Kernel from Scratch | I2C Bus — The Blood Vessels of Embedded Systems Have you ever wondered: How does a gyroscope chip or touchscreen communicate with the main controller? They are not as complex as USB, nor do they need the massive bandwidth of PCIe — they use I2C. I2C (Inter-Integrated Circuit)... » read more

Writing an OS Kernel from Scratch | SPI Bus — High-Speed Serial Communication Have you ever wondered: How does a NOR Flash chip exchange data with the CPU? It has no address lines, no complex master-slave protocol — just 4 wires, yet it can transfer data at tens of MHz. This is SPI (Serial Peripheral... » read more

Writing an OS Kernel from Scratch | Clocksource Framework — How Linux Picks the Best Clock Source Among TSC, HPET, and LAPIC Have you ever encountered this strange phenomenon: On a multi-core machine, calling clock_gettime(CLOCK_MONOTONIC) twice in succession actually returns time that went backwards? Or in a virtual machine, the system time suddenly “jumps” and... » read more

# Writing an OS Kernel from Scratch – Part 22: Device Model and devfs — Unified Management of All Hardware Devices Writing an OS Kernel from Scratch – Part 22: Device Model and devfs — Unified Management of All Hardware Devices “Your kernel has UART, VGA, IDE, TTY, but they all operate independently with no... » read more

330 – Deep Dive into Android Boot Process: From Power-On to the First App Series Navigation: 331-Bootloader | 332-init Process | 333-Zygote Have you ever thought about this: From the moment you press the power button until the desktop wallpaper appears on screen, what does the Android system go through? This is a complete chain... » read more

# Writing an OS Kernel from Scratch – Part 33: e1000 NIC Driver — Connect Your OS to the Network World! “An operating system without a network is just an information island. Today, we implement the Intel e1000 NIC driver, letting MyOS ping the outside world!” In previous chapters, we built a complete desktop system:... » read more

title: [Writing an OS Kernel from Scratch] 335 – ARM Architecture Boot: From Power-On to Kernel category: os tag: [arm, boot, embedded, u-boot] source: https://github.com/golang12306/os-kernel-from-scratch [Writing an OS Kernel from Scratch] 335 – ARM Architecture Boot: From Power-On to Kernel 1. ARM Boot Sequence Overview Embedded device boot is a layered relay race. To understand... » read more

Writing an OS Kernel from Scratch | 347: Display — From Framebuffer to GPU Abstract: The display is the most intuitive output device of a computer, but the timing, resolution, framebuffer, and GPU rendering pipeline behind it are rarely studied in depth. This article starts from CRT timing principles, explains the DRM/KMS architecture, modetest/xrandr commands,... » read more

# Quick Tip: Kernel Loaded at 1MB? Stop Joking, That Spot’s Already Taken! Have you ever wondered: Why does the OS kernel get loaded to the 1MB position? Can anyone go there? If I write a “hello world” program, what if it wants to live there too? Don’t worry, today we’re not talking about deep... » read more

354 | Interrupt Controller: How Hardware Interrupts the CPU Key Insight: You press a key, and a character appears on the screen almost simultaneously — behind this, the CPU has never been “waiting” for the keyboard. It has been running its own code the whole time, until the hardware forcibly “interrupts” it. 1. Problem: How... » read more

Writing an OS Kernel from Scratch | USB Protocol — From HID to High-Speed Devices Have you ever wondered: When you plug in a mouse, how does the system know it’s a mouse and not a keyboard? Why can a USB drive be used immediately, but an old printer requires a driver to be installed?... » read more

Writing an OS Kernel from Scratch | Context Switch — How the CPU Changes the Scene The scheduler decides to take process A off the CPU and put process B on the CPU — but how does the CPU know which line of code A paused at? Where does B resume from? How are register... » read more

331 – Android Bootloader: From Chip Power-On to Kernel Loading Series Navigation: 330-Boot Overview | 332-init Process | 333-Zygote In the previous article, we outlined the complete Android boot chain. This article focuses on the first software stage — the Bootloader. The Bootloader is the first software code to run after hardware powers on (hard-coded... » read more

Writing an OS Kernel from Scratch | Minimal Bootloader — From the Disk’s First Sector to the Kernel Entry Point Key Insight: After the computer boots, the first instruction executed by the CPU at 0xFFFF0 is neither Windows nor Linux — it’s a piece of code only 446 bytes long. It has no operating system... » read more

Writing an OS Kernel from Scratch | NIC — From PHY to Socket Have you ever thought about this process: You type in a URL, how does the data packet get sent from your computer to the server? The CPU hands the data to the network card, and the network card sends the electrical signal... » read more

Writing an OS Kernel from Scratch | System Calls — How User-Mode Triggers Kernel Code You wrote a single line write(fd, "hello", 5); in your program. This is just a C function call inside libc — how does it make its way step by step to the kernel, ultimately writing characters to the screen or... » read more

Writing an OS Kernel from Scratch | 349: SPI Bus — High-Speed Serial Communication Abstract: SPI is a higher-speed serial bus compared to I2C, commonly used with Flash storage, displays, sensors, and more. This article details SPI’s four modes, protocol timing, the Linux spidev driver, and its application in Flash storage. 1. SPI Protocol: Four-Wire... » read more

# Writing an OS Kernel from Scratch – Part 29: Mouse Driver — Adding Pointer Control to Your GUI “The keyboard is efficient, but the graphical interface can’t do without a mouse. Today, we implement a PS/2 mouse driver, enabling your window manager to support clicking and dragging!” In the previous article, we implemented a... » read more

# Writing an OS Kernel from Scratch – Part 30: Window Manager Mouse Support — Implementing Click, Drag, and Window Operations “The keyboard is efficient, but the mouse is intuitive. Today, we integrate mouse support into the window manager, achieving true graphical interaction!” In the previous article, we successfully implemented the PS/2 mouse driver and... » read more

332 – Android init Process: The First Userspace Process Series Navigation: 330-Boot Overview | 331-Bootloader | 333-Zygote Two articles ago, we covered how the Bootloader loads the kernel. Last time, we covered how the kernel decompresses, initializes hardware, and jumps to execute userspace code. Now we arrive at a pivotal role in the Android boot... » read more