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Re: many in-tree xorg packages updated
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On Jun 15, 2009, at 1:38 PM, Matthias Drochner wrote:
That reads the legacy VGA ROM and is indeed PC specific. Other archs
will have to find its bus address from the ROM BAR, hope it's valid,
enable it, map it etc.
I've found a reference for the concern I expressed in the commit msg:
PCI spec rev. 3.0 ch. 18.104.22.168 says:
In order to minimize the number of address decoders needed, a device
may share a decoder between the Expansion ROM Base Address register
and other Base Address registers.
When expansion ROM decode is enabled, the decoder is used for
to the expansion ROM and device independent software must not access
the device through any other Base Address registers.
This means reading the ROM of an active device is somewhat hairy --
would be better to use the firmware's copy if possible.
That hurts. Any idea if that's true for PCI 2.1 as well?
So we'd have to copy the ROM in the kernel in order to make sure
nobody messes with device registers while it's enabled. Or attach a
device which allows to read ROMs and takes the necessary precautions
while doing so. But then userland would have to match /dev/
rom<whatever> against whatever it uses to talk to the rest of the
device. Sounds kind of awkward.
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