Messages in this thread | | | Date | Wed, 11 Feb 2004 15:05:17 -0500 | From | Theodore Ts'o <> | Subject | Re: devfs vs udev, thoughts from a devfs user |
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On Wed, Feb 11, 2004 at 10:44:10AM +0100, Helge Hafting wrote: > Sure. Completely random device numbers will make this demand loading of > device drivers impossible. Either it won't happen (all numbers won't be > completely random, although they may get more dynamic than today) or > module loading based on device node opening will be deprecated.
It could be made to work. You could have a magic device number, say (255,255), which means "unloaded device driver", which causes a hotplug callout, and a SIGSTOP sent to the process that tried the open. The userspace program would then be responsible for loading the relevant device driver, converting the /dev file to the correct dynamic major/minor number, and then sending a SIGCONT to the process, which would then either restart the open() or the open() would return -EAGAIN.
It would be kinda hairy, in that the kernel would need to know whether or not userspace had accepted responsibility for handling these calls (if it didn't open() would just return -ENODEV as it does today). So it might not be worth doing, but if people really cared about it, it could indeed be done.
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