From: Chintan Pandya <cpandya@codeaurora.org>
To: Rasmus Villemoes <rasmus.villemoes@prevas.dk>,
robh+dt@kernel.org, frowand.list@gmail.com,
devicetree@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org
Subject: Re: [PATCH v2] of: use hash based search in of_find_node_by_phandle
Date: Fri, 26 Jan 2018 20:44:22 +0530 [thread overview]
Message-ID: <aa84e40d-5032-1d1d-6146-391ca1e5e528@codeaurora.org> (raw)
In-Reply-To: <f08592cf-5e49-e631-c481-e166b741f25e@prevas.dk>
> 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
--
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project
next prev parent reply other threads:[~2018-01-26 15:14 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-26 8:31 [PATCH v2] of: use hash based search in of_find_node_by_phandle Chintan Pandya
2018-01-26 10:57 ` Rasmus Villemoes
2018-01-26 15:14 ` Chintan Pandya [this message]
2018-01-26 15:34 ` Rob Herring
2018-01-26 21:39 ` Rob Herring
2018-01-29 7:34 ` Chintan Pandya
2018-01-29 15:10 ` Rob Herring
[not found] ` <CAL_JsqLwRYOYQ3WJ08AznZcN_BpR-udWw859W5q-CPKh=rPNFQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2018-01-29 18:18 ` Chintan Pandya
2018-01-26 23:11 ` kbuild test robot
[not found] ` <1516955496-17236-1-git-send-email-cpandya-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>
2018-01-26 23:26 ` kbuild test robot
2018-01-29 23:23 ` Frank Rowand
[not found] ` <2d877704-47c5-c1fc-1b89-976cd9b1ccaa-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2018-01-30 8:04 ` Chintan Pandya
[not found] ` <7ebd275d-07ba-1972-011a-d05e53233a01-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>
2018-01-30 18:59 ` Frank Rowand
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