%Device Driver Model
%Thadeu Cascardo

# Linux 2.6 Device Driver Model

* Design and Implementation by GregKH
* kobjects
* sysfs

# Buses

* A way to communicate with device
* Interface between Linux and hardware
* May allow hotplug of devices
* Examples:
	- USB
	- PCI
	- I2C
	- SPI
	- ACPI
	- Platform
* /sys/bus/

# Classes

* A view of the device
* Interface between Linux and user space software
* The interface may use character devices and/or sysfs or other interfaces
* Specific interface classes:
	- block devices
	- network devices
* Other classes:
	- tty
	- video4linux
	- input
	- backlight
	- rtc
* /sys/class/

# Drivers

* Implement the communication with the hardware, usually through a bus
* Present a view of the device, communicating with user space
* Basically, links the bus and the class for a given device model (or a family)

# Device

* An object representing a device in the bus or a class device
* Establishes an hierarchy through the parent link
* A class device usually has a device in the bus as its parent

# API

# Classes

* linux/device.h
* struct class
	- name
	- owner
	- dev\\_release
* class\\_create(owner, name)
* class\\_destroy(class)
* class\\_register(class)
* class\\_unregister(class)

# Devices

* struct device
	- parent
	- devt
	- class
	- release

# Devices API

* device\\_initialize(dev)
* get\\_device(dev)
* put\\_device(dev)
* dev\\_set\\_name(dev, fmt, ...)
* dev\\_set\\_drvdata(dev, drvdata)
* dev\\_get\\_drvdata(dev)

# Devices API (cont...)

* device\\_add(dev)
* device\\_del(dev)
* device\\_register(dev)
* device\\_unregister(dev)
* device\\_create(class, parent, devt, drvdata, fmt, ...)
* device\\_destroy(class, devt)

# Attributes

* struct device\\_attribute
	- attr
		* name
		* mode
	- show
	- store
* ssize\\_t show(dev, attr, char *buf)
* ssize\\_t store(dev, attr, char *buf, size\\_t count)
* sprintf
* strict\\_strtol
* strnlen

# Adding attributes

* class.dev\\_attrs
* device\\_create\\_file(dev, attr)
* device\\_remove\\_file(dev, attr)

# devtmpfs

* class.devnode
* char *devnode(dev, mode\\_t *)

# Power Management

* linux/pm.h
* dev\\_pm\\_ops
* resume
* suspend

# Buses and drivers

* Buses usually implement their API to create bus drivers
* The bus API is what should be used most of the time

# Bus

* struct bus\\_type
	- name
	- match
	- probe
	- remove
* bus\\_register
* bus\\_unregister

# Drivers

* struct device\\_driver
	- name
	- bus
	- owner
	- probe
	- remove
* driver\\_register
* driver\\_unregister

# PCI

* linux/pci.h
* struct pci\\_driver
	- name
	- id\\_table
	- probe
	- remove
* pci\\_register\\_driver(driver)
* pci\\_unregister\\_driver(driver)

# PCI IDs and device matching

* struct pci\\_device\\_id
* DEFINE\\_PCI\\_DEVICE\\_TABLE
* PCI\\_DEVICE
* PCI\\_DEVICE\\_CLASS
* struct pci\\_device\\_id