Re: [Y2038] [PATCH v4 06/10] cec: add HDMI CEC framework: y2038 question

[Arnd Bergmann <arnd@arndb.de>]

On Monday 04 May 2015 09:42:36 Hans Verkuil wrote:
> Ping! (Added Arnd to the CC list)

Hi Hans,

sorry I missed this the first time

> On 04/27/2015 09:40 AM, Hans Verkuil wrote:
> > Added the y2038 mailinglist since I would like to get their input for
> > this API.
> > 
> > Y2038 experts, can you take a look at my comment in the code below?
> > 
> > Thanks!
> 
> Arnd, I just saw your patch series adding struct __kernel_timespec to
> uapi/linux/time.h. I get the feeling that it might take a few kernel
> cycles before we have a timespec64 available in userspace. Based on that
> I think this CEC API should drop the timestamps for now and wait until
> timespec64 becomes available before adding it.
> 
> The timestamps are a nice-to-have, but not critical. So adding it later
> shouldn't be a problem. What is your opinion?

It will take a little while for the patches to make it in, I would guess
4.3 at the earliest. Using your own struct works just as well and would
be less ambiguous.

However, for timestamps, I would recommend not using timespec anyway.
Instead, just use a single 64-bit nanosecond value from ktime_get_ns()
(or ktime_get_boot_ns() if you need a time that keeps ticking across
suspend). This is more efficient to get and simpler to use as long
as you don't need to convert from nanosecond to timespec.

	Arnd