[PATCH] drm/msm: avoid using 'timespec'

[PATCH] drm/msm: avoid using 'timespec'

[Arnd Bergmann]

The timespec structure and associated interfaces are deprecated and will
be removed in the future because of the y2038 overflow.

The use of ktime_to_timespec() in timeout_to_jiffies() does not
suffer from that overflow, but is easy to avoid by just converting
the ktime_t into jiffies directly.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 drivers/gpu/drm/msm/msm_drv.h | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/msm/msm_drv.h b/drivers/gpu/drm/msm/msm_drv.h
index b2da1fbf81e0..cc8977476a41 100644
--- a/drivers/gpu/drm/msm/msm_drv.h
+++ b/drivers/gpu/drm/msm/msm_drv.h
@@ -353,8 +353,7 @@ static inline unsigned long timeout_to_jiffies(const ktime_t *timeout)
 		remaining_jiffies = 0;
 	} else {
 		ktime_t rem = ktime_sub(*timeout, now);
-		struct timespec ts = ktime_to_timespec(rem);
-		remaining_jiffies = timespec_to_jiffies(&ts);
+		remaining_jiffies = ktime_divns(rem, NSEC_PER_SEC / HZ);
 	}
 
 	return remaining_jiffies;
-- 
2.9.0

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Re: [PATCH] drm/msm: avoid using 'timespec'

[Sean Paul]

On Mon, Jun 18, 2018 at 05:39:42PM +0200, Arnd Bergmann wrote:
> The timespec structure and associated interfaces are deprecated and will
> be removed in the future because of the y2038 overflow.
> 
> The use of ktime_to_timespec() in timeout_to_jiffies() does not
> suffer from that overflow, but is easy to avoid by just converting
> the ktime_t into jiffies directly.
> 
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
>  drivers/gpu/drm/msm/msm_drv.h | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/msm_drv.h b/drivers/gpu/drm/msm/msm_drv.h
> index b2da1fbf81e0..cc8977476a41 100644
> --- a/drivers/gpu/drm/msm/msm_drv.h
> +++ b/drivers/gpu/drm/msm/msm_drv.h
> @@ -353,8 +353,7 @@ static inline unsigned long timeout_to_jiffies(const ktime_t *timeout)
>  		remaining_jiffies = 0;
>  	} else {
>  		ktime_t rem = ktime_sub(*timeout, now);
> -		struct timespec ts = ktime_to_timespec(rem);
> -		remaining_jiffies = timespec_to_jiffies(&ts);
> +		remaining_jiffies = ktime_divns(rem, NSEC_PER_SEC / HZ);

Do you need to wrap rem in ktime_to_ns() just to be safe?

Sean

>  	}
>  
>  	return remaining_jiffies;
> -- 
> 2.9.0
> 

-- 
Sean Paul, Software Engineer, Google / Chromium OS
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Re: [PATCH] drm/msm: avoid using 'timespec'

[Arnd Bergmann]

On Tue, Jul 10, 2018 at 10:47 PM, Sean Paul <seanpaul@chromium.org> wrote:
> On Mon, Jun 18, 2018 at 05:39:42PM +0200, Arnd Bergmann wrote:
>> The timespec structure and associated interfaces are deprecated and will
>> be removed in the future because of the y2038 overflow.
>>
>> The use of ktime_to_timespec() in timeout_to_jiffies() does not
>> suffer from that overflow, but is easy to avoid by just converting
>> the ktime_t into jiffies directly.
>>
>> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
>> ---
>>  drivers/gpu/drm/msm/msm_drv.h | 3 +--
>>  1 file changed, 1 insertion(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/msm/msm_drv.h b/drivers/gpu/drm/msm/msm_drv.h
>> index b2da1fbf81e0..cc8977476a41 100644
>> --- a/drivers/gpu/drm/msm/msm_drv.h
>> +++ b/drivers/gpu/drm/msm/msm_drv.h
>> @@ -353,8 +353,7 @@ static inline unsigned long timeout_to_jiffies(const ktime_t *timeout)
>>               remaining_jiffies = 0;
>>       } else {
>>               ktime_t rem = ktime_sub(*timeout, now);
>> -             struct timespec ts = ktime_to_timespec(rem);
>> -             remaining_jiffies = timespec_to_jiffies(&ts);
>> +             remaining_jiffies = ktime_divns(rem, NSEC_PER_SEC / HZ);
>
> Do you need to wrap rem in ktime_to_ns() just to be safe?

The ktime_t interfaces are still defined to use an opaque type,
as previously it was a union that could be a seconds/nanoseconds
pair depending on the architecture. These days, ktime_t is just
a 64-bit integer, so div_u64() would work just as well as ktime_divns(),
but this is the documented way to do it.

      Arnd

Re: [PATCH] drm/msm: avoid using 'timespec'

[Sean Paul]

On Tue, Jul 10, 2018 at 11:27:00PM +0200, Arnd Bergmann wrote:
> On Tue, Jul 10, 2018 at 10:47 PM, Sean Paul <seanpaul@chromium.org> wrote:
> > On Mon, Jun 18, 2018 at 05:39:42PM +0200, Arnd Bergmann wrote:
> >> The timespec structure and associated interfaces are deprecated and will
> >> be removed in the future because of the y2038 overflow.
> >>
> >> The use of ktime_to_timespec() in timeout_to_jiffies() does not
> >> suffer from that overflow, but is easy to avoid by just converting
> >> the ktime_t into jiffies directly.
> >>
> >> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> >> ---
> >>  drivers/gpu/drm/msm/msm_drv.h | 3 +--
> >>  1 file changed, 1 insertion(+), 2 deletions(-)
> >>
> >> diff --git a/drivers/gpu/drm/msm/msm_drv.h b/drivers/gpu/drm/msm/msm_drv.h
> >> index b2da1fbf81e0..cc8977476a41 100644
> >> --- a/drivers/gpu/drm/msm/msm_drv.h
> >> +++ b/drivers/gpu/drm/msm/msm_drv.h
> >> @@ -353,8 +353,7 @@ static inline unsigned long timeout_to_jiffies(const ktime_t *timeout)
> >>               remaining_jiffies = 0;
> >>       } else {
> >>               ktime_t rem = ktime_sub(*timeout, now);
> >> -             struct timespec ts = ktime_to_timespec(rem);
> >> -             remaining_jiffies = timespec_to_jiffies(&ts);
> >> +             remaining_jiffies = ktime_divns(rem, NSEC_PER_SEC / HZ);
> >
> > Do you need to wrap rem in ktime_to_ns() just to be safe?
> 
> The ktime_t interfaces are still defined to use an opaque type,
> as previously it was a union that could be a seconds/nanoseconds
> pair depending on the architecture. These days, ktime_t is just
> a 64-bit integer, so div_u64() would work just as well as ktime_divns(),
> but this is the documented way to do it.

Hey Arnd,
Ahh, ok, I think I realize my confusion now. If ktime_t was not ns, 
ktime_divns() would do the conversion for us. Since it is ns, the conversion
is a no-op (which is why I didn't see ktime_to_ns() in ktime_divns()).

Thanks for breaking that down for me,

Reviewed-by: Sean Paul <seanpaul@chromium.org>


> 
>       Arnd

-- 
Sean Paul, Software Engineer, Google / Chromium OS