On Fri, Feb 6, 2009 at 7:05 AM, Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx> wrote: > >> Is it a really a bug in X, or a misunderstanding between X and >> the kernel as to what existence of the legacy_mem file implies? >> >> I may have got this quite wrong, but to me it appears that X assumes >> that existence of the legacy_mem file implies that it will be useful; >> whereas the kernel thinks it can make the legacy_mem file available, >> even if it cannot be used for mmapping mem - which is its sole purpose? >> >> What if pci_create_legacy_files() were to call some new verification >> routine, and only create the legacy_mem file if it would be usable? >> (But perhaps that cannot be known at the time it needs to be created.) > > Well, first X should certainly not -fail- to launch if it fails to map > legacy memory, which is generally not useful anyway. That's where the > bug is. Jesse, did you have a chance to fix that yet or should I give it > a go ? > > The second problem is that if I just don't expose the legacy_mem file, > then X has no way to know whether the kernel doesn't support the > interface or whether the HW doesn't support legacy memory access. So X > will fallback to whacking /dev/mem which is even more bogus. At least > that's what I remember from last I looked at that part of X code. > > It should be a trivial fix on X side tho. I think the correct answer is the ugly one, try again. Add a new legacy_mem interface that works cleanly, update X to use it, leave the old broken one broken as it for older X to use. Dave. > > Cheers, > Ben. > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > -- To unsubscribe from this list: send the line "unsubscribe kernel-testers" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
