Re: [PATCH v4] uvcvideo: add a metadata device node

From: Hans Verkuil <hverkuil@xs4all.nl>
To: Guennadi Liakhovetski <g.liakhovetski@gmx.de>,
	Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Linux Media Mailing List <linux-media@vger.kernel.org>
Subject: Re: [PATCH v4] uvcvideo: add a metadata device node
Date: Wed, 26 Jul 2017 14:37:22 +0200	[thread overview]
Message-ID: <61413236-ac5c-474d-5dd4-5fd34f8ffcf8@xs4all.nl> (raw)
In-Reply-To: <Pine.LNX.4.64.1707261316010.6259@axis700.grange>

On 07/26/17 14:29, Guennadi Liakhovetski wrote:
> On Tue, 25 Jul 2017, Guennadi Liakhovetski wrote:
> 
> [snip]
> 
>>>> +struct uvc_meta_buf {
>>>> +	struct timespec ts;
>>>
>>> timespec has a different size on 32-bit and 64-bit architectures, so there
>>> could be issues on 32-bit userspace running on a 64-bit kernel.
>>>
>>> Additionally, on 32-bit platforms, timespec is not year 2038-safe. I thought
>>> that timespec64 was exposed to userspace nowadays, but it doesn't seem to be
>>> the case. I'm not sure how to handle this.
>>
>> Oh, that isn't good :-/ I'll have to think more about this. If you get any 
>> more ideas, I'd be glad to hear them too.
> 
> Shall we just use nanoseconds here too then, as returned by 
> timespec_to_ns(), just like in frame timestamps?

That's what I use and what Arnd recommended for use in public APIs. It's a u64, so easy
to work with.

Don't use timespec/timeval in any new public APIs, that will only cause a mess later.

Regards,

	Hans