[Desktop_architects] Re: Linux desktop, the fun thread

[Linus Torvalds]

On Fri, 16 Dec 2005, Martin Konold wrote:
>
> Am Freitag, 16. Dezember 2005 05:07 schrieb Jim Gettys:
> > What's needed is a bit of help in a kernel driver, so when the graphics
> > hardware is busy, we can be kind enough to give you the CPU back (along
> > with what to do when the hardware is next free so we can keep the
> > hardware busy rather than waiting for the next time the X server can get
> > scheduled, like on all the "old fashioned" X implementations on UNIX.
> 
> as the previous discussion did not bring up a solution I am wondering what is 
> already available in the kernel and what needs to be done in order to offer 
> the requested feature.

I _think_ some drivers effectively already do this when they enable direct 
rendering. The DRI layer does have the capability, and with many (most?) 
cards the X server actually needs to use the kernel interfaces for 2D too, 
just because it's either fully a subset of 3D, or because they share part 
of the command structure.

Of course, how well that works, I dunno. For example, at least the radeon 
driver just does a busy-wait if the command ring fills up in the kernel, 
so it's up to user space to make sure that it adds the proper "raise 
interrupt" commands every once in a while, and waits for commands to 
drain.

		Linus