Linux Kernel Architecture

Chapter 6: Device Drivers

The meanings of the elements are as follows:

❑ namepoints to a text string to uniquely identify the driver.

❑ buspoints to an object that represents the bus and provides bus-specific operations (see closer

look at this below).

❑ klist_devicesis the head of a standard list that includes thedeviceinstances of all

devices controlled by the driver. The individual devices are interlinked by means of

devices->knode_devices.

❑ knode_busis used to link all devices on a common bus.

❑ probeis a function to check whether a device that can be handled by the device driver is present

in the system.

❑ removeis invoked to remove a device from the system.

❑ shutdown,suspend,andresumeare used for power management.

Drivers are registered with the system using thedriver_registerstandard function of the kernel dis-

cussed below.

Representationof Buses

The generic driver model represents not only devices but also buses using a further data structure that is

defined as follows:

<device.h>

struct bus_type {

const char * name;

...

struct kset subsys;

struct kset drivers;

struct kset devices;

struct klist klist_devices;

struct klist klist_drivers;

...

int (*match)(struct device * dev, struct device_driver * drv);

int (*uevent)(struct device *dev, struct kobj_uevent_env *env);

int (*probe)(struct device * dev);

int (*remove)(struct device * dev);

void (*shutdown)(struct device * dev);

int (*suspend)(struct device * dev, pm_message_t state);

...

int (*resume)(struct device * dev);

...

};

❑ nameis a text name for the bus. It is especially usedto identify the bus in the sysfs filesystem.

❑ All devices and drivers associated with the bus are managed as sets using thedriversand

devicesentries. The kernel also generates two lists (klist_devicesandklist_drivers)tohold