I'm probably missing something obvious, but: Aren't phandles in practice
small consecutive integers assigned by dtc? If so, why not just have a
smallish static array mapping the small phandle values directly to
device node, instead of adding a pointer to every struct device_node? Or
one could determine the size of the array dynamically (largest seen
phandle value, capping at something sensible, e.g. 1024).
Haven't noticed this earlier !! If following is known or true, we can avoid
using hash-table and save per device_node hlish_node.
1. How to know max phandle value without traversing tree once? In
my case,
max is 1263.
2. Although, I haven't observed collision but is it like every
device_node
is associated with unique phandle value ?
In either case, one would still need to keep the code doing the
whole-tree traversal for handling large phandle values, but I think the
above should make lookup O(1) in most cases.
I would refrain doing this because that will make this API inconsistent
in terms
of time taken by different nodes. I see that people do change their device
placing in DT and that changes time taken in of_* APIs for them but
affecting
others.
Alternatively, one could just count the number of nodes with a phandle,
allocate an array of that many pointers (so the memory use is certainly
no more than if adding a pointer to each device_node), and sort it by
phandle, so one can do lookup using a binary search.
Rasmus
This is certainly doable if current approach is not welcomed due to
addition on hlish_node in device_node.
Chintan Pandya
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