On Tue, May 24, 2005 at 12:33:39PM +0100, Marty _ wrote: > never investigated udev to be quite honest, just thought it > was another form of devfs from the guide.
It is, in that it dynamically manages the /dev directory. But it does this using hotplug events from the kernel, not code inside the kernel. The default hotplug event seems to give udev a device name, and the default action for udev is to create a file in the udevdir (which we set to /dev) with that name, using the proper major, minor, and type (character vs. block). Some of these are overridden in the rules files (/dev/input/mouse* and /dev/input/mice, for example, and Alsa devices into /dev/snd), because even before devfs, the USB input devices were stuffed under /dev/input. /dev/mouse itself *seems* to be a de-facto standard. It looks like several distros created it so that they could distribute one gpm and X setup, but have it work with several different mouse types (PS/2, USB, busmouse, etc.). The PS/2 driver used to use /dev/psaux. None of that is necessary anymore with recent kernels -- ALL mouse drivers are supposed to use the kernel's input subsystem, which uses the /dev/input/* devices. So under 2.6, even loading the psaux driver will create a /dev/input/mouse0 and /dev/input/mice. Distros could just use /dev/input/mice instead of /dev/mouse. That does fall apart if you use a mouse that isn't supported by the kernel, but requires external drivers instead (some touchscreens apparently fall into this category). If those drivers don't use the kernel input subsystem, you'd need to use their device file. But whatever. > To add to your note, there isnt a difference between the two, ive just got > so used to slackware's /dev style I couldnt handle the entire directory > tree the devfs mount produces. Then you'll probably be happy to know that udev doesn't do that, at least not by default. ;-)
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