Status of VGA Arbiter and Legacy VGA I/O?

Mike Travis travis at
Fri Nov 20 13:23:24 PST 2009

Hi Adam, Jesse,

We here at SGI are getting ready to deploy the SGI Ultraviolet
system (see refs below) and the question came up about supporting
legacy I/O for multiple VGA cards.  The UV architecture requires
some additional setup when changing the "owner" of the legacy
VGA I/O space.

I've been trying to follow the progress of the VGA Arbiter, and
it's use by X, as a means of providing the kernel hook to execute
this setup.  Can you (or someone) enlighten me as to whether
a.) X still requires the use of legacy I/O [or are all accesses
being done with MMIO operations]? and b.) is the plan still to use
the VGA Arbiter as currently implemented in linux-2.6.32?

Some additional information... UV will not be supporting the
external VGA cards as vgacons, strictly as X/OpenGL devices.
There is one dedicated VGA for the system console.

Currently planned releases:  linux-2.6.32, X-7.4.1


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