linux-kernel - Re: [PATCH] usb: core: config.c: use buffer on stack rather then on heap

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Message-ID: <Pine.LNX.4.44L0.1004171041240.4980-100000@netrider.rowland.org>
Date:	Sat, 17 Apr 2010 10:42:17 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Michal Nazarewicz <mina86@...a86.com>
cc:	linux-usb@...r.kernel.org, <Linux-kernel@...r.kernel.org>,
	Greg Kroah-Hartman <gregkh@...e.de>
Subject: Re: [PATCH] usb: core: config.c: use buffer on stack rather then on
 heap

On Sat, 17 Apr 2010, Michal Nazarewicz wrote:

> usb_get_configuration() uses a temporary buffer allocated on heap
> to read USB configuration descriptor.  The buffer is just nine
> bytes an so it is a waste to allocate it on heap where it can be
> allocated on stack with the rest of local variables.  This
> simplifies the code and minimises memory usage.

This is completely wrong.  You are not allowed to do DMA to buffers on 
the stack; some architectures are not capable of handling it.

Alan Stern

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