On Thu, Jan 4, 2018 at 7:55 PM, Frank Rowand <frowand.list@xxxxxxxxx> wrote: > On 01/04/18 13:47, Kyle Evans wrote: >> On Thu, Jan 4, 2018 at 3:34 PM, Kyle Evans <kevans@xxxxxxxxxxx> wrote: >>> On Thu, Jan 4, 2018 at 2:41 PM, Kyle Evans <kevans@xxxxxxxxxxx> wrote: >>>> On Thu, Jan 4, 2018 at 2:33 PM, Frank Rowand <frowand.list@xxxxxxxxx> wrote: >>>>> [... snip ...] >>>>> >>>>> Does this remove the need for the proposed patch, or am I still >>>>> missing something? >>>> >>>> ... nope. Apparently I never tested this with this particular dtc(1) >>>> and instead just assumed it did the same as ours- allocate phandle >>>> sparsely, even with -@. That certainly removes the need for this >>>> patch, and I'm somewhat upset that I hadn't previously considered >>>> this. >>>> >>>> @David, Jon: Please disregard all of the patches along these lines... >>>> I'll fix this in our dtc, where it should be fixed. >>>> >>>> Thanks, Frank! >>> >>> Actually, I'm kind of torn on whether this is useful or not. With >>> being able to have EFI-provided FDT, it's hard to guarantee whether >>> the FDT we're provided has been compiled with GPL dtc(1) and -@. The >>> above solves this problem for most of my personal use-cases , though, >>> since I can guarantee that our FDT and U-Boot provided FDT is compiled >>> properly. >> >> Apologies for the triple post; I realized that this argument is >> inherently wrong, since we can't reference the node if there's no >> symbol anyways. >> >> The only way this might still be a good idea is to support more >> minimal cases where an implementation might prefer to not create a >> phandle for nodes that haven't been referenced. >> >> In our case, we have a function [1] that walks the tree and generates >> metadata on nodes that have phandles, under the assumption that these >> have been referenced somewhere and provides a way to more quickly >> reference these specifically through a separate linked link. >> Allocating phandles for everything as GPL dtc does adds quite a bit >> more overhead to this. >> >> [1] http://src.illumos.org/source/xref/freebsd-head/sys/dev/ofw/openfirm.c#119 > > The "-@" option does not add a phandle to _every_ node, just to nodes > that have a label: > In practice, this is still a not necessarily close superset of those that are actually going to actually get referenced in a given .dts. I note that a number of nodes will still get labelled that are unlikely to be referenced for any number of reasons. For instance, as an example [1][2][3] of one of the boards I'm working on currently, all of the ehci/ohci/mmc nodes, some set of the pio nodes... almost every single node has a label, and most of them don't need a phandle based on what is currently referenced and actually used. I note that 27 of these nodes seem to be referenced, out of 39 nodes with labels (numbers are approximate), leaving ~30% (12) of labelled nodes unreferenced. For a slightly larger example, [4][5][6][7]; 74 referenced nodes out of 113 labelled nodes, leaving ~35% (39) of labelled nodes unreferenced. This is only bothersome because it starts adding up as these things get bigger, and I don't think it really needs to. The alternative to keep phandles down to the minimum set required doesn't add much in maintenance cost or overhead from the overlay application side; especially for blobs generated by this dtc(1) that make the active decision to allocate liberally rather than conservatively. [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm/boot/dts/sun8i-a83t-bananapi-m3.dts [2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm/boot/dts/sun8i-a83t.dtsi [3] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm/boot/dts/sunxi-common-regulators.dtsi [4] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm/boot/dts/am335x-bonegreen.dts [5] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm/boot/dts/am33xx.dtsi [6] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm/boot/dts/am335x-bone-common.dtsi [7] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm/boot/dts/am335x-bonegreen-common.dtsi -- To unsubscribe from this list: send the line "unsubscribe devicetree-compiler" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
