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
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