From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from perceval.ideasonboard.com ([213.167.242.64]:54158 "EHLO perceval.ideasonboard.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727787AbeJQP5C (ORCPT ); Wed, 17 Oct 2018 11:57:02 -0400 From: Laurent Pinchart To: Heng-Ruey Hsu Cc: Mauro Carvalho Chehab , 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 Message-ID: <13883852.6N9L7C0n48@avalon> In-Reply-To: <20181017075242.21790-1-henryhsu@chromium.org> References: <20181017075242.21790-1-henryhsu@chromium.org> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Sender: linux-media-owner@vger.kernel.org List-ID: 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 > --- > 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