On Mon, Dec 5, 2011 at 9:07 PM, Graeme Russ <graeme.r...@gmail.com> wrote:
> Hi Gabe, > > On Tue, Dec 6, 2011 at 1:04 PM, Gabe Black <gabebl...@chromium.org> wrote: > > > > > > On Mon, Dec 5, 2011 at 5:49 PM, Graeme Russ <graeme.r...@gmail.com> > wrote: > >> > >> Hi Gabe, > >> > >> On Tue, Dec 6, 2011 at 12:43 PM, Gabe Black <gabebl...@chromium.org> > >> wrote: > >> > This change adds a pointer to the global data structure in x86 to > point > >> > to > >> > the device tree. This mirrors an identical pointer in ARM. > >> > >> Out of curiosity, is this paving the way for FDT support in general? > >> If so, to what extent does the Linux kernel support FDT for x86? > >> > >> I have had thoughts about looking into what Device Tree / FDT is all > >> about, and I'm wondering what it is going to bring to the table > >> (positive and negative) for x86. For example, would this, in theory, > >> depricate the boot_params structure, e820 map etc... > >> > >> Regards, > >> > >> Graeme > > > > > > > > The device tree can be used in two different ways, by u-boot and by the > > kernel. This is for use by u-boot itself and is one mechanism coreboot > can > > use to make its own runtime modification to how u-boot is set up (if > there's > > a serial console it can use, for instance), and it is fairly useful. The > > kernel has some very minimal provisions for passing in a device tree in > x86 > > through, if I remember correctly, basically a linked list of entries > which > > hang off the end of the boot_params structure. The kernel doesn't take > > I thought this list was just a linked list of more e820 entries (and that > is > what the code seems to suggest) > See: http://lxr.linux.no/linux+v3.1.4/Documentation/x86/boot.txt#L188 http://lxr.linux.no/linux+v3.1.4/Documentation/x86/boot.txt#L636 http://lxr.linux.no/linux+v3.1.4/arch/x86/include/asm/bootparam.h#L12 It's type 2. > > > advantage of it at all, so it wouldn't really be useful to pass one in. > > There are times when it would be a good solution to certain problems but > the > > kernel would have to actually be set up to take advantage of it first. > > Does UEFI support device trees? If so, I wonder if this is the future of > Linux and x86 support is somewhat inevitable? > I don't know but I don't think so. It wouldn't surprise me *that* much to see device trees in x86 eventually, but there's a long way to go before that happens. From what I heard it took quite a bit of pushing to get it in for the architectures that already support it now. I would be surprised if it happened any time soon. > > Regards, > > Graeme >
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