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Old 03-02-09, 02:54 PM   #7
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Join Date: Aug 2008
Posts: 47
Default Re: Feature Request: KMS support

Originally Posted by AaronP View Post
I actually looked into this a little bit, and it looks like "KMS" is one of those things like AIGLX where we already have what the acronym stands for and what people really want is something else. Here, what people seem to be asking for are two things:
  1. An fbdev driver.
  2. A seamless transition from the fbdev console to X.
Step 2 would be implemented entirely within our driver and shouldn't be too much trouble, at least for modern GPUs. Step 1 requires some more research and we're investigating whether it's possible and worth it. Other things people have been talking about, such as a graphical kernel crash dump, will require some more work and I've been discussing it with some of the X folks to make sure it can work reliably.
I'm sure it could be implemented that way, but I don't think thats what it is at all. KMS/GEM/DRI2 means the kernel is responsible for all device access. Mode setting, memory/object management. Userspace no longer makes ANY direct device access, and X can run as a regular user.

The KMS part of the solution is mainly mode setting. It makes the kernel manage the graphics card, such that it does the actual mode setting, and now that userspace isn't involved, it'll also support proper kernel level sleep and hibernate (its really hard to do when userspace has its hands in the pie), it also means the kernel can print useful diagnostic messages to your screen, even with graphics running.

Have you looked at Waland yet, and what its aiming to do? If you haven't you probably should.

@perfectska04, I'm not sure who told you that KMS will improve boot times. I wouldn't expect boot times to change at all, except for them possibly slowing down a bit due to the extra workload induced by Plymouth.
It will prove perceived boot times in most cases. No ugly flickering, just a steady (potentially very pretty) progress display.

One of the distros has also played with moving XDM/KDM/GDMs startup to before most services, so perceived boot time goes way down, even if total boot time actually goes up.
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