linux-kernel - Re: [PATCH] media: uvcvideo: Fix annotation for uvc_video_clock

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Message-ID: <20200101172833.GG6226@pendragon.ideasonboard.com>
Date:   Wed, 1 Jan 2020 19:28:33 +0200
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Jun Chen <ptchentw@...il.com>
Cc:     mchehab@...nel.org, linux-media@...r.kernel.org,
        linux-kernel@...r.kernel.org, Jun Chen <jun.chen@...ics.com>
Subject: Re: [PATCH] media: uvcvideo: Fix annotation for
 uvc_video_clock_update()

Hello Jun,

Thank you for the patch.

On Wed, Dec 25, 2019 at 10:34:17AM +0800, Jun Chen wrote:
> From: Jun Chen <jun.chen@...ics.com>
> 
> The formula (2) is to convert from SOF to host clock,
> it should be fix as
> "TS = ((TS2 - TS1) * SOF + TS1 * SOF2 - TS2 * SOF1) / (SOF2 - SOF1)"
> 
> Signed-off-by: Jun Chen <jun.chen@...ics.com>

Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>

and applied to my tree.

> ---
>  drivers/media/usb/uvc/uvc_video.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
> index 8fa77a8..a3150da 100644
> --- a/drivers/media/usb/uvc/uvc_video.c
> +++ b/drivers/media/usb/uvc/uvc_video.c
> @@ -622,7 +622,7 @@ static u16 uvc_video_clock_host_sof(const struct uvc_clock_sample *sample)
>   * to avoid losing precision in the division. Similarly, the host timestamp is
>   * computed with
>   *
> - * TS = ((TS2 - TS1) * PTS + TS1 * SOF2 - TS2 * SOF1) / (SOF2 - SOF1)	     (2)
> + * TS = ((TS2 - TS1) * SOF + TS1 * SOF2 - TS2 * SOF1) / (SOF2 - SOF1)	     (2)
>   *
>   * SOF values are coded on 11 bits by USB. We extend their precision with 16
>   * decimal bits, leading to a 11.16 coding.

-- 
Regards,

Laurent Pinchart