On Saturday 16 May 2009 19:14:17 pk wrote: > Alan McKinnon wrote: > > I'm not sure who's criticizing DeviceKit, but it isn't me :-) > > I guess it was me... :-) > > I find this thread interesting: > http://lists.freedesktop.org/archives/xorg/2009-May/045561.html > > ...especially this: > http://lists.freedesktop.org/archives/xorg/2009-May/045574.html > > Which seems like a much more sane way... to me. I don't know what BSD > and other platforms use (instead of Udev) but I'm sure one could come up > with a common API.
Sometimes you have to make several horrendous errors to know what to not do and thereby deduce what you should do - the only version 3 rule of thumb :-) From threads involving the hal maintainers I get the idea that the problem is not so much the idea of hal, but rather it's implementation. And then there's those fdi files... As I see it, at the bottom of the stack you have a kernel and at the top a user space app (the X server will do for an example). Plug in a USB device that the app can use, and the kernel needs to make a node in /dev for it if it's not already there. The kernel should not be interrogating the device for all possible info - that is expensive - and doesn't need to. It only needs enough info to know what driver, major and minor numbers to use. X OTOH, can successfully use much more info. If you have a 19 button mouse, it would like to know and could even use it as a one-handed keyboard (extreme example). So the current model uses udev as the interface to the kernel's nodes and HAL as the interface to exactly what hardware you have. Seems pretty sane for the most usual use case. At some point in the stack you will need the OS-dependant part, my guess is the best place is between hal and udev. Only Linux uses udev, but all OSes use something in that spot. And if not, they have static nodes. Meanwhile we have an acknowledged problem with hal - it's too complex, too many things have been shoved into it that were never catered for in the design, configuration is horrific - and the devs are having their usual spirited debate about how best to approach a solution. This is perfectly normal and perfectly healthy -- alan dot mckinnon at gmail dot com
