linux-kernel - Re: [PATCH 1/1] UIO: Add a write() function to enable/disable interrupts

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Message-ID: <20080523115815.GA6932@digi.com>
Date:	Fri, 23 May 2008 13:58:15 +0200
From:	Uwe Kleine-König <Uwe.Kleine-Koenig@...i.com>
To:	Tom Spink <tspink@...il.com>
CC:	"Hans J. Koch" <hjk@...utronix.de>, <linux-kernel@...r.kernel.org>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Jan Altenberg <jan.altenberg@...utronix.de>,
	Thomas Gleixner <tglx@...utronix.de>,
	Magnus Damm <magnus.damm@...il.com>
Subject: Re: [PATCH 1/1] UIO: Add a write() function to enable/disable interrupts

Hello Tom,

> > Tom Spink wrote:
> >> The added benefit is that the code becomes less complex, as you don't
> >> have to check buffer sizes and copy the integer from userspace.
> > AFAIK this is wrong.  You need to copy the integer from userspace in
> > uio_ioctl.  Actually it's a value coming from user space, so you need to
> > do it somewhere.
> 
> Not really in this case.  It's not a *pointer* to a value in
> userspace, so you don't need to copy anything.  If it was being used
> to point to a memory location holding a value, then yes, it would need
> to be copied across.  But in this case, it's just being used to pass
> across 1 or 0.
ah, OK, you're right.  Thanks for correcting my correction :-)

Uwe

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Uwe Kleine-König, Software Engineer
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