> I have a very simple question . How does > Linux know that it has to load driver 'x' for > device 'y'. It doesn't :) Drivers can either be built into the kernel or built as loadable modules. Drivers that are part of the kernel are initialized early in the boot sequence - even if there are no devices that a driver can support (kernel doesn't know). The driver has to check if it can support any of the devices on the system. This can be done through bus specific interfaces (like PCI) or some other device specific way. If it finds one or more devices, it initializes them and registers itself with the kernel. If the driver is configured as a module, it can be loaded manually (insmod or modprobe) or automatically when needed. Again, in the first case, kernel doesn't have to know what devices are supported by the driver. The driver claims the devices that it can manage. The second case is slightly different. When a user program tries to access a device (usually thorugh the device file in /dev) but no corresponding driver is registered, the kernel tries to load a driver module. Of course, the kernel does not know the actual driver name. So it uses generic names like 'eth0', 'char-major-135' or 'scsi_hostadapter'. The mapping between these names and actual module names is provided in a file (/etc/modules.conf or something similar). Once the module is loaded, it initializes the usual way and claims the devices that it can manage. Hope this helps, Ravi. __________________________________________________ Do you Yahoo!? Yahoo! Web Hosting - Let the expert host your site http://webhosting.yahoo.com -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
