Re: [PATCH 00/28] nios2 Linux kernel port

[Chung-Lin Tang]

On 2014/4/22 07:20 PM, Ley Foon Tan wrote:
> On Tue, Apr 22, 2014 at 6:56 PM, Arnd Bergmann <arnd@xxxxxxxx> wrote:
>> On Tuesday 22 April 2014 18:37:11 Ley Foon Tan wrote:
>>> Hi Arnd and Peter Anvin,
>>>
>>> Other than 64-bit time_t, clock_t and suseconds_t, can you confirm
>>> that we don't need to have 64 bit off_t? See detail in link below.
>>> I can submit the patches for 64-bit time changes
>>> (include/asm-generic/posix_types.h and other archs) if everyone is
>>> agreed on this.
>>
>> Yes.
> Okay, will doing that.
> 
>>
>>> Excerpt from https://lkml.org/lkml/2012/11/14/358 :
>>> "Obviously, we want to use 64-bit off_t, but this is achieved already
>>> through loff_t, which is used in all places in the asm-generic
>>> ABI anyway (the syscalls using off_t are stripped out). I don't
>>> think we want to have the other ones set to 64 bit on ARC or Meta,
>>> although I'm not 100% sure about ino_t and nlink_t. "
>>
>> This is all still true. You should have no syscall using 'off_t',
>> only loff_t.
>>
>> I still don't know whether we would want 32 or 64 bit ino_t and nlink_t
>> for new architectures. It seems it would gain very little, but have
>> a noticeable overhead.
> Anyone have comment on this?
> Chung-Lin (in CC list) is our nios2 toolchain maintainer. Do you have
> any comment for 32 or 64 bit ino_t and nlink_t?
> We will update the toolchain to support 64-bit time_t, so we hope that
> any other toolchain change can happen in one time.

For ino_t, 32-bit users of linux-generic glibc already use struct
stat64, stat64(), etc. to align with 64-bit targets, so in terms of the
glibc/kernel interface it doesn't matter much.  The in-kernel usage of
the ino_t type should be of more concern here.

nlink_t appears to be always defined as u32 in <linux/types.h>, not sure
if changing it to arch-overridable is reasonable.

Chung-Lin



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