linux-kernel - Re: [PATCH] media: si21xx: use time_after

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Message-ID: <a940cf331d493c8755454e8557c2330901e30986.camel@perches.com>
Date:   Thu, 10 Feb 2022 01:07:19 -0800
From:   Joe Perches <joe@...ches.com>
To:     Qing Wang <wangqing@...o.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] media: si21xx: use time_after_eq() instead of jiffies
 judgment

On Thu, 2022-02-10 at 00:31 -0800, Qing Wang wrote:
> From: Wang Qing <wangqing@...o.com>
> 
> It is better to use time_xxx() directly instead of jiffies judgment
> for understanding.
[]
> diff --git a/drivers/media/dvb-frontends/si21xx.c b/drivers/media/dvb-frontends/si21xx.c
[]
> @@ -336,7 +336,7 @@ static int si21xx_wait_diseqc_idle(struct si21xx_state *state, int timeout)
>  	dprintk("%s\n", __func__);
>  
>  	while ((si21_readreg(state, LNB_CTRL_REG_1) & 0x8) == 8) {
> -		if (jiffies - start > timeout) {
> +		if (time_after(jiffies, start + timeout)) {
>  			dprintk("%s: timeout!!\n", __func__);
>  			return -ETIMEDOUT;
>  		}

Appreciate all the conversions (IMO it should have been sent as
a block of patches with a cover letter instead of independent
unrelated patches) but wouldn't all of these be simpler and more
consistent using a style where the addition is done once and the
timeout test is something like:

	unsigned long end = jiffies + timeout;

	while (foo) {
		if (time_after(jiffies, end)) {
			error_msg(...)
			return -ETIMEDOUT;
		}
		bar...;
	}