From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arnd Bergmann Subject: Re: [PATCH 01/25] asm-generic: Change time_t and clock_t to 64 bit Date: Tue, 13 May 2014 12:21:40 +0200 Message-ID: <4465265.lUhYuYrZG4@wuerfel> References: <1399971456-3941-1-git-send-email-lftan@altera.com> <5371EAEB.5030100@imgtec.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7Bit Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Ley Foon Tan Cc: James Hogan , Linux-Arch , LKML , Chung-Lin Tang , Thomas Gleixner List-Id: linux-arch.vger.kernel.org On Tuesday 13 May 2014 18:17:40 Ley Foon Tan wrote: > On Tue, May 13, 2014 at 5:50 PM, James Hogan wrote: > > Hi, > > > > On 13/05/14 10:32, Ley Foon Tan wrote: > >> On Tue, May 13, 2014 at 5:15 PM, James Hogan wrote: > >>> On 13 May 2014 10:02, Ley Foon Tan wrote: > >>>> /* > >>>> + * Use 64 bit time_t and clock_t as default. 32 bit users can provide an override to > >>>> + * define these as "long" if needed. > >>>> + */ > >>>> +#ifndef __kernel_time_t > >>>> +typedef long long __kernel_time_t; > >>>> +#endif > >>>> + > >>>> +#ifndef __kernel_clock_t > >>>> +typedef long long __kernel_clock_t; > >>>> +#endif > >>> > >>> I think having this as the first patch in the series will break > >>> bisection for existing 32-bit arches. This needs to be done in such a > >>> way that at no intermediate commit are __kernel_time_t or > >>> __kernel_clock_t the wrong size for existing arches, e.g. by having a > >>> first patch which makes the typedefs conditional but leaves them as > >>> __kernel_long_t, and a final patch that changes the default after all > >>> the arches have got their overrides in place. > >> > >> Your suggestion is something as below? > > > > Yeh, although I like Thomas' idea better, then each existing 32-bit arch > > can just select the Kconfig symbol to get the smaller type. > > > > IIRC Kconfig won't even complain if you select a symbol which doesn't > > exist yet. > When we export this posix_types.h file for user software, they need to > define this config, eg: CONFIG_32BIT_TIME to use 32 bit time. Is this > what we want to do? No, this doesn't really work: You can't use CONFIG_* symbols in user-visible header files. Arnd From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mout.kundenserver.de ([212.227.126.130]:55699 "EHLO mout.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760245AbaEMKV6 (ORCPT ); Tue, 13 May 2014 06:21:58 -0400 From: Arnd Bergmann Subject: Re: [PATCH 01/25] asm-generic: Change time_t and clock_t to 64 bit Date: Tue, 13 May 2014 12:21:40 +0200 Message-ID: <4465265.lUhYuYrZG4@wuerfel> In-Reply-To: References: <1399971456-3941-1-git-send-email-lftan@altera.com> <5371EAEB.5030100@imgtec.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Sender: linux-arch-owner@vger.kernel.org List-ID: To: Ley Foon Tan Cc: James Hogan , Linux-Arch , LKML , Chung-Lin Tang , Thomas Gleixner Message-ID: <20140513102140.PsQlBp4rnu_mUuXf5dlng2TJtgwuOeStfl3CcRKwtk4@z> On Tuesday 13 May 2014 18:17:40 Ley Foon Tan wrote: > On Tue, May 13, 2014 at 5:50 PM, James Hogan wrote: > > Hi, > > > > On 13/05/14 10:32, Ley Foon Tan wrote: > >> On Tue, May 13, 2014 at 5:15 PM, James Hogan wrote: > >>> On 13 May 2014 10:02, Ley Foon Tan wrote: > >>>> /* > >>>> + * Use 64 bit time_t and clock_t as default. 32 bit users can provide an override to > >>>> + * define these as "long" if needed. > >>>> + */ > >>>> +#ifndef __kernel_time_t > >>>> +typedef long long __kernel_time_t; > >>>> +#endif > >>>> + > >>>> +#ifndef __kernel_clock_t > >>>> +typedef long long __kernel_clock_t; > >>>> +#endif > >>> > >>> I think having this as the first patch in the series will break > >>> bisection for existing 32-bit arches. This needs to be done in such a > >>> way that at no intermediate commit are __kernel_time_t or > >>> __kernel_clock_t the wrong size for existing arches, e.g. by having a > >>> first patch which makes the typedefs conditional but leaves them as > >>> __kernel_long_t, and a final patch that changes the default after all > >>> the arches have got their overrides in place. > >> > >> Your suggestion is something as below? > > > > Yeh, although I like Thomas' idea better, then each existing 32-bit arch > > can just select the Kconfig symbol to get the smaller type. > > > > IIRC Kconfig won't even complain if you select a symbol which doesn't > > exist yet. > When we export this posix_types.h file for user software, they need to > define this config, eg: CONFIG_32BIT_TIME to use 32 bit time. Is this > what we want to do? No, this doesn't really work: You can't use CONFIG_* symbols in user-visible header files. Arnd