Messages in this thread | | | Date | Sun, 13 Jan 2008 01:43:04 -0500 | From | Jeff Garzik <> | Subject | Re: [Patch v2] Make PCI extended config space (MMCONFIG) a driver opt-in |
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Matthew Wilcox wrote: > On Sat, Jan 12, 2008 at 08:42:48PM -0800, Arjan van de Ven wrote: >> Wanne bet there'll be devices that screw this up? THere's devices that even screwed >> up the 64-256 region after all. > > I don't know if they 'screwed it up'. There are devices that misbehave > when registers are read from pci config space. But this was never > guaranteed to be a safe thing to do; it gradualy became clear that > people expected to be able to read random registers and manufacturers > responded accordingly, but I don't think you were ever guaranteed to be > able to peek at bits of config space arbitrarily.
Quite correct... Reading registers can have all sorts of side effects, for example clearing chip conditions.
Jeff
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