linux-kernel - Re: [PATCH v3] bus: uniphier-system-bus: add UniPhier System Bus driver

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Date:	Wed, 9 Dec 2015 12:56:43 +0900
From:	Masahiro Yamada <yamada.masahiro@...ionext.com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	arm@...nel.org, Mark Rutland <mark.rutland@....com>,
	devicetree@...r.kernel.org, Kumar Gala <galak@...eaurora.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v3] bus: uniphier-system-bus: add UniPhier System Bus driver

Hi Arnd,

2015-12-09 1:59 GMT+09:00 Arnd Bergmann <arnd@...db.de>:
>
> Just a little thought about one thing I found odd:
>
>> +static int uniphier_system_bus_check_overlap(
>> +                                     struct uniphier_system_bus_priv tmp)
>> +{
>
> Did you intentionally pass this by value?

Yes, I did not want to disturb the original one.

It is copied to a temporary storage, and sorted by the base address,
and discarded after the overlap checking.

But, you are right.   It is possible (and simpler)
to check the region overlap without sorting.


> Maybe do it explicitly using a pointer
> and memcpy to a local variable, which has a similar effect. Alternatively
> just check each newly probed child node for conflicts with any of the
> previous children. That is slightly more expensive at O(n^2) instead of O(n)
> but n is always small here and you can avoid sorting first.

Good idea.  I simplified this function in v4.



-- 
Best Regards
Masahiro Yamada
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