Re: [PATCH] media: rc: Replace timeval with ktime_t in imon.c

Chunyan Zhang
2014-12-18T09:38:22Z

On Thu, Dec 18, 2014 at 3:50 PM, Arnd Bergmann <arnd@linaro.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:
>
>> http://lkml.iu.edu//hypermail/linux/kernel/1412.2/00625.html
>>
>> Signed-off-by: Chunyan Zhang <zhang.chunyan@linaro.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