Am Dienstag, 15. September 2009 13:24:42 schrieb Niamathullah sharief: > Hi friends, > I am some doubts regarding USB port. How the devices are fetching > drivers When we insert the USB device into the USB port. From where it > will search first? How it will get the driver?I am novice please help > me Very well. Two related processes achieve that goal. Whenever a device is plugged in, the following sequence happens: a) khubd is woken b) khubd generates a hotplug event c) the event is delivered to udev (in user space) d) udev processes the event Step (d) usually involves udev loading a driver for the device. Udev knows which driver to load from a table computed from the device aliases in the drivers at comile time. Secondly, inside the kernel devices are probed. A device is probed, when: a) it is plugged in b) the user request a probe via usbfs or sysfs c) a new driver is loaded and no driver is bound to the device Strictly speaking two cases need to be considered 1) the driver has been loaded before the device is plugged in - the kernel itself will bind the driver to the device 2) no driver for the device has been loaded - udev loads it and the loading of the new driver will cause a round of probing. HTH Oliver -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
