linux-kernel - Re: [PATCH] media: rc: Replace timeval with ktime

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Message-ID: <20141218090053.68a0aad6@recife.lan>
Date:	Thu, 18 Dec 2014 09:00:53 -0200
From:	Mauro Carvalho Chehab <mchehab@....samsung.com>
To:	Chunyan Zhang <zhang.chunyan@...aro.org>
Cc:	Arnd Bergmann <arnd@...aro.org>, david@...deman.nu,
	uli-lirc@...-eckhardt.de, hans.verkuil@...co.com,
	julia.lawall@...6.fr, Himangi Saraogi <himangi774@...il.com>,
	Alexey Khoroshilov <khoroshilov@...ras.ru>, joe@...ches.com,
	John Stultz <john.stultz@...aro.org>,
	linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
	Lyra Zhang <zhang.lyra@...il.com>
Subject: Re: [PATCH] media: rc: Replace timeval with ktime_t in imon.c

Em Thu, 18 Dec 2014 17:38:14 +0800
Chunyan Zhang <zhang.chunyan@...aro.org> escreveu:

> On Thu, Dec 18, 2014 at 3:50 PM, Arnd Bergmann <arnd@...aro.org> wrote:
> > On Thursday 18 December 2014 11:37:13 Chunyan Zhang wrote:
> >> This patch changes the 32-bit time type (timeval) to the 64-bit one
> >> (ktime_t), since 32-bit time types will break in the year 2038.
> >>
> >> I use ktime_t instead of all uses of timeval in imon.c
> >>
> >> This patch also changes do_gettimeofday() to ktime_get() accordingly,
> >> since ktime_get returns a ktime_t, but do_gettimeofday returns a
> >> struct timeval, and the other reason is that ktime_get() uses
> >> the monotonic clock.
> >>
> >> This patch use a new function which is provided by another patch listed below
> >> to get the millisecond time difference.
> >
> > The patch looks great. Just a few small details that could still be
> > improved:

Yes, patch looks OK. After addressing the bits pointed by Arnd:

Acked-by: Mauro Carvalho Chehab <mchehab@....samsung.com>

Feel free to merge via y2038 tree.

> >
> >> http://lkml.iu.edu//hypermail/linux/kernel/1412.2/00625.html
> >>
> >> Signed-off-by: Chunyan Zhang <zhang.chunyan@...aro.org>
> >
> > In general, when you give a mailing list link, use the 'Link' tag
> > under your Signed-off-by line, like
> >
> > Link: http://lkml.iu.edu//hypermail/linux/kernel/1412.2/00625.html
> >
> > It's not used much yet, but getting more popular and seems useful to me.
> >
> > In this particular case, when you have patches that depend on one
> > another, you can make do it even better by sending all three patches
> > as a series with a [PATCH 0/3] cover letter.
> >
> OK, I'll send a patch-set including these three patches
> 
> > If the media maintainers can provide an Ack for this patch, I would
> > suggest to queue it up in the y2038 branch together with your first
> > patch that it depends on.
> >
> >> @@ -1191,16 +1168,16 @@ static inline int tv2int(const struct timeval *a, const struct timeval *b)
> >>   */
> >>  static int stabilize(int a, int b, u16 timeout, u16 threshold)
> >>  {
> >> -     struct timeval ct;
> >> -     static struct timeval prev_time = {0, 0};
> >> -     static struct timeval hit_time  = {0, 0};
> >> +     ktime_t ct;
> >> +     static ktime_t prev_time = {0};
> >> +     static ktime_t hit_time  = {0};
> >>       static int x, y, prev_result, hits;
> >>       int result = 0;
> >
> > The "= {0}" part here is redundant, since static variables are always
> > initialized to zero. Normally, adding the explicit initializer can
> > help readability, but in this case I would leave it out because it shows
> > implementation details of ktime_t that are better hidden from drivers.
> >
> OK, I'll modify them soon
> 
> Thanks,
> Chunyan
> 
> >> @@ -1596,9 +1573,9 @@ static void imon_incoming_packet(struct imon_context *ictx,
> >>       int i;
> >>       u64 scancode;
> >>       int press_type = 0;
> >> -     int msec;
> >> -     struct timeval t;
> >> -     static struct timeval prev_time = { 0, 0 };
> >> +     long msec;
> >> +     ktime_t t;
> >> +     static ktime_t prev_time = {0};
> >>       u8 ktype;
> >
> > Same thing here of course.
> >
> >         Arnd
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