linux-kernel - Re: V4L2 drivers: potentially dangerous and inefficient msecs_to

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Message-ID: <4AAEB6F0.4080706@gmail.com>
Date:	Mon, 14 Sep 2009 23:34:40 +0200
From:	Jiri Slaby <jirislaby@...il.com>
To:	Andreas Mohr <andi@...as.de>
CC:	Guennadi Liakhovetski <g.liakhovetski@....de>,
	Mauro Carvalho Chehab <mchehab@...radead.org>,
	Luca Risolia <luca.risolia@...dio.unibo.it>,
	linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: V4L2 drivers: potentially dangerous and inefficient	msecs_to_jiffies()
 calculation

On 09/14/2009 11:07 PM, Andreas Mohr wrote:
> ./drivers/media/video/zc0301/zc0301_core.c
> do
>                             cam->module_param.frame_timeout *
>                             1000 * msecs_to_jiffies(1) );
> multiple times each.
> What they should do instead is
> frame_timeout * msecs_to_jiffies(1000), I'd think.

In fact, msecs_to_jiffies(frame_timeout * 1000) makes much more sense.

> msecs_to_jiffies(1) is quite a bit too boldly assuming
> that all of the msecs_to_jiffies(x) implementation branches
> always round up.

They do, don't they?
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