Re: [RFC PATCH 2/7] sound: core: Avoid using timespec for struct snd_pcm_status

From: Takashi Iwai <tiwai@suse.de>
To: "Baolin Wang" <baolin.wang@linaro.org>
Cc: <perex@perex.cz>, <alsa-devel@alsa-project.org>, <arnd@arndb.de>,
	<arvind.yadav.cs@gmail.com>, <bhumirks@gmail.com>,
	<deepa.kernel@gmail.com>, <lgirdwood@gmail.com>,
	<dharageswari.r@intel.com>, <gudishax.kranthikumar@intel.com>,
	<guneshwor.o.singh@intel.com>, <hardik.t.shah@intel.com>,
	<jeeja.kp@intel.com>, <naveen.m@intel.com>,
	<vinod.koul@intel.com>, <broonie@kernel.org>, <mingo@kernel.org>,
	<dan.carpenter@oracle.com>, <o-takashi@sakamocchi.jp>,
	<fabf@skynet.be>, <elfring@users.sourceforge.net>,
	<linux-kernel@vger.kernel.org>
Subject: Re: [RFC PATCH 2/7] sound: core: Avoid using timespec for struct snd_pcm_status
Date: Fri, 22 Sep 2017 11:31:25 +0200	[thread overview]
Message-ID: <s5hlgl7dqqa.wl-tiwai@suse.de> (raw)
In-Reply-To: <78aa803db47d99c2bee1a4dc8d426621324785b8.1505973912.git.baolin.wang@linaro.org>

On Thu, 21 Sep 2017 08:18:04 +0200,
Baolin Wang wrote:
> 
> The struct snd_pcm_status will use 'timespec' type variables to record
> timestamp, which is not year 2038 safe on 32bits system.
> 
> Userspace will use SNDRV_PCM_IOCTL_STATUS and SNDRV_PCM_IOCTL_STATUS_EXT
> as commands to issue ioctl() to fill the 'snd_pcm_status' structure in
> userspace. The command number is always defined through _IOR/_IOW/IORW,
> so when userspace changes the definition of 'struct timespec' to use
> 64-bit types, the command number also changes.
> 
> Thus in the kernel, we now need to define two versions of each such ioctl
> and corresponding ioctl commands to handle 32bit time_t and 64bit time_t
> in native mode:
> struct snd_pcm_status32 {
> 	......
> 	struct { s32 tv_sec; s32 tv_nsec; } trigger_tstamp;
> 	struct { s32 tv_sec; s32 tv_nsec; } tstamp;
> 	......
> }
> 
> struct snd_pcm_status64 {
> 	......
> 	struct { s64 tv_sec; s64 tv_nsec; } trigger_tstamp;
> 	struct { s64 tv_sec; s64 tv_nsec; } tstamp;
> 	......
> }

I'm confused.  It's different from timespec64?  So 32bit user-space
would need to use a new own-type timespec instead of the standard
timespec that is compliant with y2038?

thanks,

Takashi