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From: Hans Verkuil <hverkuil@xs4all.nl>
To: Arnd Bergmann <arnd@arndb.de>
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 11:52:28 +0200	[thread overview]
Message-ID: <55FBDEDC.8040204@xs4all.nl> (raw)
In-Reply-To: <9019880.VVdOR6WRt1@wuerfel>

On 09/18/15 11:43, Arnd Bergmann wrote:
> 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?

Right. Drivers only see the new struct, and only v4l2-ioctl.c (and possible
v4l2-compat-ioctl32.c) see the old ones.

BTW, I will probably pick up patches 4 and 6 for 4.4. That should help a bit.

Regards,

	Hans

>> 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  9:52 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
2015-09-18  9:52             ` Hans Verkuil [this message]
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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