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Date: Thu, 09 Nov 2017 19:11:26 +0100 From: Takashi Iwai <tiwai@...e.de> To: Arnd Bergmann <arnd@...db.de> Cc: Baolin Wang <baolin.wang@...aro.org>, Jaroslav Kysela <perex@...ex.cz>, Fabian Frederick <fabf@...net.be>, Arvind Yadav <arvind.yadav.cs@...il.com>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, alsa-devel@...a-project.org, Vinod Koul <vinod.koul@...el.com>, hardik.t.shah@...el.com, guneshwor.o.singh@...el.com, Liam Girdwood <lgirdwood@...il.com>, SF Markus Elfring <elfring@...rs.sourceforge.net>, gudishax.kranthikumar@...el.com, Mark Brown <broonie@...nel.org>, Bhumika Goyal <bhumirks@...il.com>, Naveen M <naveen.m@...el.com>, jeeja.kp@...el.com, Takashi Sakamoto <o-takashi@...amocchi.jp>, subhransu.s.prusty@...el.com, Ingo Molnar <mingo@...nel.org>, Dan Carpenter <dan.carpenter@...cle.com> Subject: Re: [alsa-devel] [RFC PATCH v2 7/7] sound: core: Avoid using timespec for struct snd_timer_tread On Thu, 09 Nov 2017 18:01:47 +0100, Arnd Bergmann wrote: > > On Thu, Nov 9, 2017 at 5:52 PM, Takashi Iwai <tiwai@...e.de> 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
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