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

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Message-ID: <20180710204736.GU20303@art_vandelay>
Date:   Tue, 10 Jul 2018 16:47:36 -0400
From:   Sean Paul <seanpaul@...omium.org>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Rob Clark <robdclark@...il.com>, David Airlie <airlied@...ux.ie>,
        y2038@...ts.linaro.org, Jordan Crouse <jcrouse@...eaurora.org>,
        Sean Paul <seanpaul@...omium.org>,
        linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/msm: avoid using 'timespec'

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@...db.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