On Thu, 2006-08-03 at 16:49 -0400, Brown, Len wrote: > >On Thu, Aug 03, 2006 at 10:25:43PM +0200, Adrian Bunk wrote: > >> ACPI_CUSTOM_DSDT seems to be the most interesting case. > >> It's anyway not usable for distribution kernels, and AFAIR the ACPI > >> people prefer to get the kernel working with all original DSDTs > >> (which usually work with at least one other OS) than letting > >> the people workaround the problem by using a custom DSDT. > > > >Not true at all. For SuSE kernels, we have a patch that lets people > >load a new DSDT from initramfs due to broken machines requiring a > >replacement in order to work properly. > > CONFIG_ACPI_CUSTOM_DSDT allows hackers to debug their system > by building a modified DSDT into the kernel to over-ride what > came with the system. It would make no sense for a distro > to use it, unless the distro were shipping only on 1 model machine. > This technique is necessary for debugging, but makes no > sense for production. > > The initramfs method shipped by SuSE is more flexible, allowing > the hacker to stick the DSDT image in the initrd and use it > without re-compiling the kernel. > > I have refused to accept the initrd patch into Linux many times, > and always will. > > I've advised SuSE many times that they should not be shipping it, > as it means that their supported OS is running on modified firmware -- > which, by definition, they can not support. Tainting the kernel if done so should be sufficient. > Indeed, one could view > this method as couter-productive to the evolution of Linux -- > since it is our stated goal to run on the same machines that Windows > runs on -- without requiring customers to modify those machines > to run Linux. There are three reasons for the initrd patch (last one also applies for the compile in functionality): 1) There might be "BIOS bugs" that will never get fixed: https://bugzilla.novell.com/show_bug.cgi?id=160671 (Because it's an obvious BIOS bug, "compatibility" fixing it could make things worse). 2) There might be "ACPICA/kernel bugs" that take a while until they get fixed: This happens often. There comes out a new machine, using AML in a slightly other way, we need to fix it in kernel/ACPICA. Until the patch appears mainline may take a month or two. Until the distro of your choice that makes use of the fix comes out might take half a year or more... And backporting ACPICA fixes to older kernels is currently not possible as ACPICA patches appear in a big bunch of some thousand lines patches. But this hopefully changes soon. In my mind come: - alias broken in certain cases https://bugziall.novell.com/show_bug.cgi?id=113099 - recon amount of elements in packages https://bugzilla.novell.com/show_bug.cgi?id=189488 - wrong offsets at Field and Operation Region declarations -> should be compatible for quite a while now - ... 3) Debugging. This is why at least compile in or via initrd must be provided in mainline kernel IMHO. Intel people themselves ask the bug reporter to override ACPI tables with a patched table to debug the system. Do you really think ripping out all overriding functionality from the kernel is a good idea? Thomas It is true that some users are happy with a fixed DSDT, even you tell them to find the root cause..., but sooner or later they always come back. - To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
