From: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
To: Heng-Ruey Hsu <henryhsu@chromium.org>
Cc: Mauro Carvalho Chehab <mchehab@kernel.org>,
linux-media@vger.kernel.org, linux-kernel@vger.kernel.org,
jcliang@chromium.org, tfiga@chromium.org
Subject: Re: [PATCH] media: uvcvideo: Add boottime clock support
Date: Wed, 17 Oct 2018 11:02:40 +0300 [thread overview]
Message-ID: <13883852.6N9L7C0n48@avalon> (raw)
In-Reply-To: <20181017075242.21790-1-henryhsu@chromium.org>
Hi Heng-Ruey,
Thank you for the patch.
On Wednesday, 17 October 2018 10:52:42 EEST Heng-Ruey Hsu wrote:
> Android requires camera timestamps to be reported with
> CLOCK_BOOTTIME to sync timestamp with other sensor sources.
What's the rationale behind this, why can't CLOCK_MONOTONIC work ? If the
monotonic clock has shortcomings that make its use impossible for proper
synchronization, then we should consider switching to CLOCK_BOOTTIME globally
in V4L2, not in selected drivers only.
> Signed-off-by: Heng-Ruey Hsu <henryhsu@chromium.org>
> ---
> drivers/media/usb/uvc/uvc_driver.c | 4 ++++
> drivers/media/usb/uvc/uvc_video.c | 2 ++
> 2 files changed, 6 insertions(+)
>
> diff --git a/drivers/media/usb/uvc/uvc_driver.c
> b/drivers/media/usb/uvc/uvc_driver.c index d46dc432456c..a9658f38c586
> 100644
> --- a/drivers/media/usb/uvc/uvc_driver.c
> +++ b/drivers/media/usb/uvc/uvc_driver.c
> @@ -2287,6 +2287,8 @@ static int uvc_clock_param_get(char *buffer, const
> struct kernel_param *kp) {
> if (uvc_clock_param == CLOCK_MONOTONIC)
> return sprintf(buffer, "CLOCK_MONOTONIC");
> + else if (uvc_clock_param == CLOCK_BOOTTIME)
> + return sprintf(buffer, "CLOCK_BOOTTIME");
> else
> return sprintf(buffer, "CLOCK_REALTIME");
> }
> @@ -2298,6 +2300,8 @@ static int uvc_clock_param_set(const char *val, const
> struct kernel_param *kp)
>
> if (strcasecmp(val, "monotonic") == 0)
> uvc_clock_param = CLOCK_MONOTONIC;
> + else if (strcasecmp(val, "boottime") == 0)
> + uvc_clock_param = CLOCK_BOOTTIME;
> else if (strcasecmp(val, "realtime") == 0)
> uvc_clock_param = CLOCK_REALTIME;
> else
> diff --git a/drivers/media/usb/uvc/uvc_video.c
> b/drivers/media/usb/uvc/uvc_video.c index 86a99f461fd8..d4248d5cd9cd 100644
> --- a/drivers/media/usb/uvc/uvc_video.c
> +++ b/drivers/media/usb/uvc/uvc_video.c
> @@ -425,6 +425,8 @@ static inline ktime_t uvc_video_get_time(void)
> {
> if (uvc_clock_param == CLOCK_MONOTONIC)
> return ktime_get();
> + else if (uvc_clock_param == CLOCK_BOOTTIME)
> + return ktime_get_boottime();
> else
> return ktime_get_real();
> }
--
Regards,
Laurent Pinchart
next prev parent reply other threads:[~2018-10-17 15:57 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-17 7:52 [PATCH] media: uvcvideo: Add boottime clock support Heng-Ruey Hsu
2018-10-17 8:02 ` Laurent Pinchart [this message]
2018-10-17 8:28 ` Tomasz Figa
2018-10-17 20:50 ` Laurent Pinchart
2018-10-18 4:31 ` Tomasz Figa
2018-10-18 17:28 ` Alexandru M Stan
2018-11-01 14:03 ` Laurent Pinchart
2018-11-01 14:30 ` Tomasz Figa
2018-11-01 15:03 ` Lars-Peter Clausen
2018-11-23 14:46 ` Tomasz Figa
2019-03-06 6:09 ` Tomasz Figa
2019-03-13 1:24 ` Laurent Pinchart
2019-03-13 2:38 ` Tomasz Figa
2019-08-06 4:15 ` Tomasz Figa
2019-08-06 8:34 ` Kieran Bingham
2019-08-07 13:38 ` Tomasz Figa
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