[PATCH 1/2] Kernel/time: Introduce a new timestamp function local_time_seconds()

[PATCH 1/2] Kernel/time: Introduce a new timestamp function local_time_seconds()

[Gu Zheng]

>From 18072c1c3506a7e37ee485307a2c343efe5af4d0 Mon Sep 17 00:00:00 2001
From: Gu Zheng <guz.fnst@cn.fujitsu.com>
Date: Mon, 13 May 2013 15:45:24 +0900
Subject: [PATCH 1/2] Kernel/time: Introduce a new timestamp function local_time_seconds()

Introduce a new timestamp function local_time_seconds() to hide the conversion of system time in UTC to local time seconds.

Signed-off-by: Gu Zheng <guz.fnst@cn.fujitsu.com>
---
 include/linux/time.h |    1 +
 kernel/time.c        |   11 +++++++++++
 2 files changed, 12 insertions(+), 0 deletions(-)

diff --git a/include/linux/time.h b/include/linux/time.h
index 22d81b3..1aec534 100644
--- a/include/linux/time.h
+++ b/include/linux/time.h
@@ -271,4 +271,5 @@ static __always_inline void timespec_add_ns(struct timespec *a, u64 ns)
 	a->tv_nsec = ns;
 }
 
+extern u32 local_time_seconds(void);
 #endif
diff --git a/kernel/time.c b/kernel/time.c
index d3617db..715377d 100644
--- a/kernel/time.c
+++ b/kernel/time.c
@@ -712,3 +712,14 @@ struct timespec timespec_add_safe(const struct timespec lhs,
 
 	return res;
 }
+
+/*
+ * Convert system time in UTC to local time seconds.
+ */
+u32 local_time_seconds(void)
+{
+	struct timeval utc;
+	do_gettimeofday(&utc);
+	return (u32)(utc.tv_sec - (sys_tz.tz_minuteswest * 60));
+}
+EXPORT_SYMBOL(local_time_seconds);
-- 
1.7.1

Re: [PATCH 1/2] Kernel/time: Introduce a new timestamp function local_time_seconds()

[John Stultz]

On 05/14/2013 12:45 AM, Gu Zheng wrote:
>  From 18072c1c3506a7e37ee485307a2c343efe5af4d0 Mon Sep 17 00:00:00 2001
> From: Gu Zheng <guz.fnst@cn.fujitsu.com>
> Date: Mon, 13 May 2013 15:45:24 +0900
> Subject: [PATCH 1/2] Kernel/time: Introduce a new timestamp function local_time_seconds()
>
> Introduce a new timestamp function local_time_seconds() to hide the conversion of system time in UTC to local time seconds.

So, why is this useful/needed?

thanks
-john

Re: [PATCH 1/2] Kernel/time: Introduce a new timestamp function local_time_seconds()

[Gu Zheng]

On 05/14/2013 11:57 PM, John Stultz wrote:

> On 05/14/2013 12:45 AM, Gu Zheng wrote:
>>  From 18072c1c3506a7e37ee485307a2c343efe5af4d0 Mon Sep 17 00:00:00 2001
>> From: Gu Zheng <guz.fnst@cn.fujitsu.com>
>> Date: Mon, 13 May 2013 15:45:24 +0900
>> Subject: [PATCH 1/2] Kernel/time: Introduce a new timestamp function local_time_seconds()
>>
>> Introduce a new timestamp function local_time_seconds() to hide the conversion of system time in UTC to local time seconds.
> 
> So, why is this useful/needed?

Hi John,
   There are some subsystems use local time seconds as a timestamp, such as scsi(refer to:http://www.spinics.net/lists/linux-scsi/msg66089.html),
and so do many out-of-kernel-tree code I think.

Best regards,
Gu

> 
> thanks
> -john
> 
> 

Re: [PATCH 1/2] Kernel/time: Introduce a new timestamp function local_time_seconds()

[James Bottomley]

On Wed, 2013-05-15 at 11:32 +0800, Gu Zheng wrote:
> On 05/14/2013 11:57 PM, John Stultz wrote:
> 
> > On 05/14/2013 12:45 AM, Gu Zheng wrote:
> >>  From 18072c1c3506a7e37ee485307a2c343efe5af4d0 Mon Sep 17 00:00:00 2001
> >> From: Gu Zheng <guz.fnst@cn.fujitsu.com>
> >> Date: Mon, 13 May 2013 15:45:24 +0900
> >> Subject: [PATCH 1/2] Kernel/time: Introduce a new timestamp function local_time_seconds()
> >>
> >> Introduce a new timestamp function local_time_seconds() to hide the conversion of system time in UTC to local time seconds.
> > 
> > So, why is this useful/needed?
> 
> Hi John,
>    There are some subsystems use local time seconds as a timestamp,
> such as scsi(refer
> to:http://www.spinics.net/lists/linux-scsi/msg66089.html),
> and so do many out-of-kernel-tree code I think.

I don't think the 3ware drivers, which are the only ones that do this
actually care.  I think jiffies to seconds would suit the event
timestamps equally well, so I don't really see a need to make this a
formal kernel export given that it's only a single driver family in the
entirety of the kernel.

James