From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753709AbdKISLd (ORCPT ); Thu, 9 Nov 2017 13:11:33 -0500 Received: from mx2.suse.de ([195.135.220.15]:36657 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753576AbdKISLb (ORCPT ); Thu, 9 Nov 2017 13:11:31 -0500 Date: Thu, 09 Nov 2017 19:11:26 +0100 Message-ID: From: Takashi Iwai To: Arnd Bergmann Cc: Baolin Wang , Jaroslav Kysela , Fabian Frederick , Arvind Yadav , Linux Kernel Mailing List , alsa-devel@alsa-project.org, Vinod Koul , hardik.t.shah@intel.com, guneshwor.o.singh@intel.com, Liam Girdwood , SF Markus Elfring , gudishax.kranthikumar@intel.com, Mark Brown , Bhumika Goyal , Naveen M , jeeja.kp@intel.com, Takashi Sakamoto , subhransu.s.prusty@intel.com, Ingo Molnar , Dan Carpenter Subject: Re: [alsa-devel] [RFC PATCH v2 7/7] sound: core: Avoid using timespec for struct snd_timer_tread In-Reply-To: References: User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI/1.14.6 (Maruoka) FLIM/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL/10.8 Emacs/25.3 (x86_64-suse-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI 1.14.6 - "Maruoka") Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 09 Nov 2017 18:01:47 +0100, Arnd Bergmann wrote: > > On Thu, Nov 9, 2017 at 5:52 PM, Takashi Iwai wrote: > > On Mon, 06 Nov 2017 17:33:26 +0100, > > >> --- a/include/uapi/sound/asound.h > >> +++ b/include/uapi/sound/asound.h > >> @@ -306,10 +306,19 @@ typedef int __bitwise snd_pcm_state_t; > >> > >> enum { > >> SNDRV_PCM_MMAP_OFFSET_DATA = 0x00000000, > >> - SNDRV_PCM_MMAP_OFFSET_STATUS = 0x80000000, > >> + SNDRV_PCM_MMAP_OFFSET_STATUS_OLD = 0x80000000, > >> SNDRV_PCM_MMAP_OFFSET_CONTROL = 0x81000000, > >> + SNDRV_PCM_MMAP_OFFSET_STATUS64 = 0x82000000, > >> }; > >> > >> +#if __BITS_PER_LONG == 64 > >> +#define SNDRV_PCM_MMAP_OFFSET_STATUS SNDRV_PCM_MMAP_OFFSET_STATUS_OLD > >> +#else > >> +#define SNDRV_PCM_MMAP_OFFSET_STATUS ((sizeof(time_t) > > >> sizeof(__kernel_long_t)) ? \ > >> + SNDRV_PCM_MMAP_OFFSET_STATUS64 : \ > >> + SNDRV_PCM_MMAP_OFFSET_STATUS_OLD) > >> +#endif > >> + > >> union snd_pcm_sync_id { > >> unsigned char id[16]; > >> unsigned short id16[8]; > >> > >> Does that make sense? > > > > Yeah, that should work. > > > > But can we make the flip without the dynamic sizeof() comparison but > > some ifdef? The above doesn't allow the usage with switch(), for > > example. > > > > IOW, is there any macro indicating the 64bit user time_t? > > There is a macro defined by the C library, but so far we have not > started relying on it in kernel headers, because there is no guarantee > that this symbol is visible before sys/time.h has been included, > and there are some cases where it's possible to include a kernel > header before sys/time.h. > > In case of sound/asound.h, that should be no problem since we rely > on having seen the definition on 'struct timeval' already today, and > that must come from sys/time.h. Then we just need to make sure that > all C libraries define the same macro. > > Are you sure about the switch()/case problem? I thought that worked > in C99, the only problem would be using the macro outside of a > function, e.g. as initalizer for a variable Hmm, OK it seems working. But, honestly speaking, it's too scaring. I'm OK if it were only in the kernel local code. But it's the API/ABI definition, which is referred by user-space... A more solid condition would be really appreciated. thanks, Takashi