linux-kernel - Re: range operation of outer cache when start >= end?

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Message-ID: <20160108150618.GL19062@n2100.arm.linux.org.uk>
Date:	Fri, 8 Jan 2016 15:06:18 +0000
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc:	linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
	Arnd Bergmann <arnd@...db.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: range operation of outer cache when start >= end?

On Fri, Jan 08, 2016 at 11:54:30AM +0900, Masahiro Yamada wrote:
> I know I am nitpicking.  Forgive me if I am asking a silly question.
> 
> 
> How should the outer-cache handle such an insane case like  start >= end?

Passing start >= end isn't defined, code should not pass start >= end.

> Assumed answers are:
> 
> [1] Do not care about that.  It should never happen.  If it does, fix
> the caller.

This applies.  What situation are you seeing start >= end?

What you will get with the existing code is potentially some cache
cleaning and a sync, but nothing apart from that.  __l2c210_op_pa_range()
becomes a no-op of start >= end.  However, that behaviour is not
guaranteed.

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