On Wed, 19 Nov 2014 09:24:41 +0100 , Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> wrote: > On 19 November 2014 00:11, Rob Herring <rob.herring@xxxxxxxxxx> wrote: > > On Tue, Nov 18, 2014 at 4:11 PM, Grant Likely <grant.likely@xxxxxxxxxx> wrote: > >> On Tue, 18 Nov 2014 17:25:45 +0000 > >> , Mark Rutland <mark.rutland@xxxxxxx> > >> wrote: > >>> On Tue, Nov 18, 2014 at 04:51:45PM +0000, Grant Likely wrote: > >>> > On Fri, 14 Nov 2014 18:05:35 +0100 > >>> > , Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> > >>> > wrote: > >>> > > Create a new /sys entry '/sys/firmware/fdt' to export the FDT blob > >>> > > that was passed to the kernel by the bootloader. This allows userland > >>> > > applications such as kexec to access the raw binary. > > > > [...] > > > >>> > * It also helps with exposing the reserved map to userspace, but kexec > >>> > has done without that feature for years, and it is in the process of > >>> > being deprecated in favour of /reserved-memory anyway. > >>> > >>> This is the first I'd heard of the reserve map being deprecated, and > >>> we're going to have DTs with reserved map entries for a long time going > >>> forwards. > >> > >> Deprecated, not removed or disabled. It will still work pretty much > >> forever, but users should be encouraged to move to the reserve-memory > >> tree. > > > > I thought you had said reserve map was still the right way for memory > > the kernel should never touch. > > > >>> Can't we expose the header fields under something like > >>> /sys/firmware/devicetree/dtb-header/, parallel to the usual > >>> /sys/firmware/devicetree/base for nodes? > >> > >> We could do that too. > >> > >> Honestly though, I'm just unsure of what the best thing to do is. If you > >> and a few others tell me that, "no, exporting the raw dtb is the right > >> thing to do", then I'll be okay, merge the patch and sleep properly. > > > > I always sleep better when others can take the blame. > > > > What happens when we rev the dtb format? Is the ABI the blob or the > > format of the blob? > > > > I lean towards we should add this. This is providing what is "in the > > firmware" while /proc/devicetree provides the live tree state > > including overlays. > > > > Well, my pov is that FDT != devicetree ever since we started (ab)using > the FDT container format to pass just the UEFI entry points to the > kernel. > The boot protocol describes what should be passed in x0, and /that/ is > what we expose in /sys/firmware/fdt, regardless of how the kernel > decided to configure itself. > (perhaps we need to fix the wording in the document to refer to FDT not dtb) > > So that also means I don't care about memreserve vs reserved-memory or > other DT specific details: as long as x0 points to something libfdt > understands at boot, we expose it and not interpret it any further. Alright, my doubt is quelled. Merged. g. -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
