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From: Arnd Bergmann <arnd@arndb.de>
To: Hans Verkuil <hverkuil@xs4all.nl>
Cc: linux-samsung-soc@vger.kernel.org,
	Mauro Carvalho Chehab <mchehab@osg.samsung.com>,
	y2038@lists.linaro.org, linux-api@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-media@vger.kernel.org
Subject: Re: [PATCH v2 7/9] [media] v4l2: introduce v4l2_timeval
Date: Fri, 18 Sep 2015 11:43:24 +0200	[thread overview]
Message-ID: <9019880.VVdOR6WRt1@wuerfel> (raw)
In-Reply-To: <55FBD90C.3020301@xs4all.nl>

On Friday 18 September 2015 11:27:40 Hans Verkuil wrote:
> Ah, OK. Got it.
> 
> I think this is dependent on the upcoming media workshop next month. If we
> decide to redesign v4l2_buffer anyway, then we can avoid timeval completely.
> And the only place where we would need to convert it in the compat code
> hidden in the v4l2 core (likely v4l2-ioctl.c).

Ah, I think I understood the idea now, I missed that earlier when you mention
the idea.

So what you are saying here is that you could come up with a new unambiguous
(using only __u32 and __u64 types and no pointers) format that gets exposed
to a new set of ioctls, and then change the handling of the existing three
formats (native 64-bit, traditional 32-bit, and 32-bit with 64-bit time_t)
so they get converted into the new format by the common ioctl handling code?

> I am not really keen on having v4l2_timeval in all these drivers. I would
> have to check them anyway since I suspect that in several drivers the local
> timeval variable can be avoided by rewriting that part of the driver.

I've tried to do that for all the drivers where I could find an easy solution
in patch 6/9, but I'm sure you can do it for a couple more.

We could also do a lightweight redesign and use 'timespec64' internally
in all the drivers and then convert that to 'timeval' or the 64-bit
format of that in the ioctl handler. This is also something I tried at
some point but then found it a bit more intuitive to leave the normal ioctl
path alone and have an explicit type.

> Personally I am in favor of a redesigned v4l2_buffer: it's awkward to use
> with multiplanar formats, there is cruft in there that can be removed (timecode),
> and there is little space for additions (HW-specific timecodes, more buffer
> meta data, etc).
> 
> We'll see.

Ok.

	Arnd
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  reply	other threads:[~2015-09-18  9:43 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-09-17 21:19 [PATCH v2 0/9] [media] y2038 conversion for subsystem Arnd Bergmann
2015-09-17 21:19 ` [PATCH v2 1/9] [media] dvb: use ktime_t for internal timeout Arnd Bergmann
2015-09-17 21:19 ` [PATCH v2 2/9] [media] dvb: remove unused systime() function Arnd Bergmann
2015-09-17 21:19 ` [PATCH v2 3/9] [media] dvb: don't use 'time_t' in event ioctl Arnd Bergmann
2015-09-17 21:19 ` [PATCH v2 4/9] [media] exynos4-is: use monotonic timestamps as advertized Arnd Bergmann
2015-09-17 21:19 ` [PATCH v2 5/9] [media] make VIDIOC_DQEVENT work with 64-bit time_t Arnd Bergmann
2015-09-17 21:19 ` [PATCH v2 6/9] [media] use v4l2_get_timestamp where possible Arnd Bergmann
2015-09-17 21:19 ` [PATCH v2 7/9] [media] v4l2: introduce v4l2_timeval Arnd Bergmann
     [not found]   ` <1442524780-781677-8-git-send-email-arnd-r2nGTMty4D4@public.gmane.org>
2015-09-18  8:05     ` Hans Verkuil
2015-09-18  9:09       ` Arnd Bergmann
2015-09-18  9:27         ` Hans Verkuil
2015-09-18  9:43           ` Arnd Bergmann [this message]
2015-09-18  9:52             ` Hans Verkuil
2015-09-18 10:08               ` Arnd Bergmann
2015-09-18 10:22                 ` Hans Verkuil
     [not found] ` <1442524780-781677-1-git-send-email-arnd-r2nGTMty4D4@public.gmane.org>
2015-09-17 21:19   ` [PATCH v2 8/9] [media] handle 64-bit time_t in v4l2_buffer Arnd Bergmann
2015-09-18  7:18     ` Hans Verkuil
2015-09-18  9:26       ` Arnd Bergmann
2015-09-18  9:49         ` Hans Verkuil
2015-09-18 10:14           ` Arnd Bergmann
2015-09-17 21:19 ` [PATCH v2 9/9] [media] omap3isp: support 64-bit version of omap3isp_stat_data Arnd Bergmann
     [not found]   ` <1442524780-781677-10-git-send-email-arnd-r2nGTMty4D4@public.gmane.org>
2015-11-09 20:09     ` Laurent Pinchart
2015-11-09 20:30       ` Arnd Bergmann
2015-11-09 21:04         ` [Y2038] " Laurent Pinchart

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