[Bug 2737] New: Cyrix and nsc drivers should be enhanced to redirect to the other driver when needed

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https://bugs.freedesktop.org/show_bug.cgi?id=2737          
     
           Summary: Cyrix and nsc drivers should be enhanced to redirect to
                    the other driver when needed
           Product: xorg
           Version: CVS_head
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: * Other
        AssignedTo: xorg-bugzilla-noise at freedesktop.org
        ReportedBy: mharris at www.linux.org.uk


The cyrix and nsc drivers have PCI ID overlap.  Natsemi reused the same PCI ID
with the same graphics chip, but changed the BIOS in an incompatible way
from what I understand.  The net result is that hardware autodetection software
that relies solely on the PCI device and vendor ID and subvendor/device ID,
and even revision fields in PCI config space, can not uniquely distinguish
between certain cyrix hardware and nsc hardware.

00:12.4 Class 0300: 1078:0104
Subsystem: 1078:0001
Flags: medium devsel
Memory at 40800000 (32-bit, non-prefetchable) [size=8M]

The only way to detect wether the hardware should use the cyrix or nsc
drivers is to do:

   outb(0x35, 0x3D4)
   check inb(0x3d5) = C
   outb(0x36, 0x3D5)
   check inb(0x3D5) = X  - if so VSA2 -> NSC driver


Both the cyrix and nsc drivers should be enhanced to do this autodetection
and if the wrong chip is detected, the driver should autoreload the
correct driver something like the "ati" driver does if possible.  Otherwise
it should steadfastly fail to load and print an error telling the user the
right driver to use.

The place to put this type of code is in the drivers, not in the configuration
software IMHO.          
     
     
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