linux-kernel - Re: [PATCH] media: stk1160: Fixed high volume of stk1160_dbg messages

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Message-ID: <ZT6q0xhAsHmX9GZQ@equinox>
Date:   Sun, 29 Oct 2023 18:56:19 +0000
From:   Phillip Potter <phil@...lpotter.co.uk>
To:     Ghanshyam Agrawal <ghanshyam1898@...il.com>
Cc:     ezequiel@...guardiasur.com.ar, mchehab@...nel.org,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        linux-kernel@...r.kernel.org, linux-media@...r.kernel.org
Subject: Re: [PATCH] media: stk1160: Fixed high volume of stk1160_dbg messages

On Sun, Oct 29, 2023 at 08:06:04PM +0530, Ghanshyam Agrawal wrote:
> The function stk1160_dbg gets called too many times, which causes
> the output to get flooded with messages. Since stk1160_dbg uses
> printk, it is now replaced with printk_ratelimited directly.
> 
> Signed-off-by: Ghanshyam Agrawal <ghanshyam1898@...il.com>
> ---
>  drivers/media/usb/stk1160/stk1160-video.c | 13 +------------
>  1 file changed, 1 insertion(+), 12 deletions(-)
> 
> diff --git a/drivers/media/usb/stk1160/stk1160-video.c b/drivers/media/usb/stk1160/stk1160-video.c
> index 4e966f6bf608..f5b75f380c19 100644
> --- a/drivers/media/usb/stk1160/stk1160-video.c
> +++ b/drivers/media/usb/stk1160/stk1160-video.c
> @@ -105,17 +105,6 @@ void stk1160_copy_video(struct stk1160 *dev, u8 *src, int len)
>  	u8 *dst = buf->mem;
>  	int remain;
>  
> -	/*
> -	 * TODO: These stk1160_dbg are very spammy!
> -	 * We should 1) check why we are getting them
> -	 * and 2) add ratelimit.
> -	 *
> -	 * UPDATE: One of the reasons (the only one?) for getting these
> -	 * is incorrect standard (mismatch between expected and configured).
> -	 * So perhaps, we could add a counter for errors. When the counter
> -	 * reaches some value, we simply stop streaming.
> -	 */
> -
>  	len -= 4;
>  	src += 4;
>  
> @@ -151,7 +140,7 @@ void stk1160_copy_video(struct stk1160 *dev, u8 *src, int len)
>  
>  	/* Let the bug hunt begin! sanity checks! */
>  	if (lencopy < 0) {
> -		stk1160_dbg("copy skipped: negative lencopy\n");
> +		printk_ratelimited("copy skipped: negative lencopy\n");
>  		return;
>  	}
>  
> -- 
> 2.25.1
> 
> _______________________________________________
> Linux-kernel-mentees mailing list
> Linux-kernel-mentees@...ts.linuxfoundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/linux-kernel-mentees

Hi Ghanshyam,

As we've conversed about this via other comms channels, thought I'd
offer my comments here for what they are worth. Thanks for the patch
firstly.

Few things I would change though:
(1) Keep the comment around perhaps, but modify/move it, to specify the
    reason for the ratelimiting is caused by standard mismatches.
    Perhaps also leave a note about the possibility of it being due to
    other problems also, given the comment says "the only one?" posed as
    a question.
(2) For consistency, probably worth making use of KERN_WARNING in your
    new printk_ratelimited call.

All the best.

Regards,
Phil

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