linux-kernel - Re: [PATCH] irda: irda-usb: use msecs_to

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Message-ID: <1432045935.2870.152.camel@perches.com>
Date:	Tue, 19 May 2015 07:32:15 -0700
From:	Joe Perches <joe@...ches.com>
To:	Nicholas Mc Guire <hofrat@...dl.org>
Cc:	Samuel Ortiz <samuel@...tiz.org>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] irda: irda-usb: use msecs_to_jiffies for conversions

On Tue, 2015-05-19 at 12:51 +0200, Nicholas Mc Guire wrote:
> Converting milliseconds to jiffies by "val * HZ / 1000" is technically
> is not a clean solution as it does not handle all corner cases correctly.
> By changing the conversion to use msecs_to_jiffies(val) conversion is
> correct in all cases.
> 
> in the current code: 
>   mod_timer(&self->rx_defer_timer, jiffies + (10 * HZ / 1000));
> for HZ < 100 (e.g. CONFIG_HZ == 64|32 in alpha) this effectively results 
> in no delay at all.
[]
> diff --git a/drivers/net/irda/irda-usb.c b/drivers/net/irda/irda-usb.c
[]
> @@ -848,7 +848,9 @@ static void irda_usb_receive(struct urb *urb)
>  		 * Jean II */
>  		self->rx_defer_timer.function = irda_usb_rx_defer_expired;
>  		self->rx_defer_timer.data = (unsigned long) urb;
> -		mod_timer(&self->rx_defer_timer, jiffies + (10 * HZ / 1000));
> +		mod_timer(&self->rx_defer_timer,
> +			  jiffies + (msecs_to_jiffies(10)));

The unnecessary () around msecs_to_jiffies could be removed.


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