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

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Date:	Mon, 21 Apr 2014 19:52:38 +0200
From:	Richard Weinberger <richard.weinberger@...il.com>
To:	Ley Foon Tan <lftan@...era.com>
Cc:	Pavel Machek <pavel@...x.de>,
	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

On Mon, Apr 21, 2014 at 7:32 PM, Ley Foon Tan <lftan@...era.com> wrote:
> On Sun, Apr 20, 2014 at 12:09 AM, Pavel Machek <pavel@...x.de> wrote:
>>> +/* Additional Nios II specific syscalls. */
>>> +#define __NR_cacheflush (__NR_arch_specific_syscall)
>>> +__SYSCALL(__NR_cacheflush, sys_cacheflush)
>>
>> I guess you should Cc: Michael Kerrisk on this one.
> CC him this email.
>
>>
>> Also... explanation why you need this syscall while other
>> architectures live happily without it would be nice.
> This syscall exist in nios2 port since old days and some users already
> used it for sometimes.
> Like mentioned by Greet, 12 our of 28 architectures provide such a syscall.
>
>>> +/* 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.

-- 
Thanks,
//richard
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