add LKD 17

README.md

@@ -62,7 +62,8 @@ Linux Kernel Development
 13. [Chapter 13: The Virtual Filesystem](./linux-kernel-development/chapter-13.md)
 14. [Chapter 14: The Block I/O Layer](./linux-kernel-development/chapter-14.md)
 15. [Chapter 15: The Process Address Space](./linux-kernel-development/chapter-15.md)
-16. (-) [Chapter 16: The Page Cache and Page Writeback](./linux-kernel-development/chapter-16.md)
+16. [Chapter 16: The Page Cache and Page Writeback](./linux-kernel-development/chapter-16.md)
+17. (-) [Chapter 17: Devices and Modules](./linux-kernel-development/chapter-17.md)
 
 Paper Review
 ---

linux-kernel-development/chapter-17.md

@@ -0,0 +1,29 @@
+# Chapter 17: Devices and Modules
+
+- `Device types`: Classifications used in all Unix systems to unify behavior of common devices
+- `Modules`: The mechanism by which the Linux kernel can load and unload object code on demand
+- `Kernel objects`: Support for adding simple object-oriented behavior and a parent/child relationship to kernel data structures
+- `Sysfs`: A filesystem representation of the system's device tree
+
+
+## Device Types
+In Linux, as with all Unix systems, devices are classified into one of three types:
+- `Block devices`: Often abbreviated `blkdevs`, `block devices` are addressable in device-specified chunks called `blocks` and generally support `seeking`, the random access of data.
+- `Character devices`: Often abbreviated `cdevs`, character devices are generally not addressable, providing access to data only as a stream, generally of characters (bytes).
+- `Network devices`: Sometimes called `Ethernet devices` after the most common type of network devices, `network devices` provide access to a network via a physical adapter and a specific protocol.
+
+
+## Modules
+The Linux kernel is modular, supporting the dynamic insertion and removal of code from itself at runtime. Related subroutines, data, and entry and exit points are grouped together in a single binary image, a loadable kernel object, called a `module`.
+
+
+## The Device Model
+A significant new feature in the 2.6 Linux kernel is the addition of a unified `device model`. The device model provides a single mechanism for representing devices and describing their topology in the system.
+
+
+
+## sysfs
+The `sysfs filesystem` is an in-memory virtual filesystem that provides a view of the kobject hierarchy. It enables users to view the device topology of their system as a simple filesystem. Using attributes, kobjects can export files that enable kernel variables to be read from and optionally written to.
+
+The magic behind `sysfs` is simply tying kobjects to directory entries via the dentry
+member inside each kobject.