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@xxxxxxxxxxxx>
> ---
> 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
