linux-kernel - Re: [PATCH 16/28] nios2: System calls handling

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Message-ID: <20140421204835.GB22181@amd.pavel.ucw.cz>
Date:	Mon, 21 Apr 2014 22:48:35 +0200
From:	Pavel Machek <pavel@...x.de>
To:	Richard Weinberger <richard.weinberger@...il.com>
Cc:	Ley Foon Tan <lftan@...era.com>,
	Linux-Arch <linux-arch@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	cltang@...esourcery.com,
	Michael Kerrisk-manpages <mtk.manpages@...il.com>
Subject: Re: [PATCH 16/28] nios2: System calls handling

> >>> +/* sys_cacheflush -- flush the processor cache. */
> >>> +asmlinkage int sys_cacheflush(unsigned long addr, unsigned long len,
> >>> +                             unsigned int op)
> >>> +{
> >>> +     struct vm_area_struct *vma;
> >>> +
> >>> +     if (len == 0)
> >>> +             return 0;
> >>
> >> op is being ignored? You should remove it... or if (op) return -EINVAL
> >> if you want future extensions.
> > Yes, op argument is being ignored. Okay, will add the return -EINVAL
> > if op is non-zero.
> 
> Be careful. If existing applications already use this and maybe pass a
> dummy value
> to it you break them.

Well.. of course, but passing ignored integer to syscall, that can be
never used is beyond ugly. NAK-level ugly.

If it is so, you can never ever use the argument, and might as well
remove it (depending on your calling convention, it should not break
anything.)

								Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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