linux-kernel - Re: RFC: [PATCH] resource: ensure MMIO exclusivity for device drivers

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Date:	Mon, 27 Oct 2008 16:31:58 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Arjan van de Ven <arjan@...radead.org>
Cc:	linux-kernel@...r.kernel.org, Alan Cox <alan@...rguk.ukuu.org.uk>,
	torvalds@...ux-foundation.org, Matthew Wilcox <matthew@....cx>,
	Jesse Barnes <jbarnes@...tuousgeek.org>
Subject: Re: RFC: [PATCH] resource: ensure MMIO exclusivity for device
	drivers


* Arjan van de Ven <arjan@...radead.org> wrote:

> 
> From: Arjan van de Ven <arjan@...ux.intel.com>
> Date: Wed, 22 Oct 2008 19:55:31 -0700
> Subject: [PATCH] resource: ensure MMIO exclusivity for device drivers
> 
> Device drivers that use pci_request_regions() (and similar APIs) have a
> reasonable expectation that they are the only ones accessing their device.
> As part of the e1000e hunt, we were afraid that some userland (X or some
> bootsplash stuff) was mapping the MMIO region that the driver thought it
> had exclusively via /dev/mem or via various sysfs resource mappings.
> 
> This patch adds the option for device drivers to cause their reserved
> regions to be on the "banned from /dev/mem use" list, so now both kernel memory
> and device-exclusive MMIO regions are banned.
> NOTE: This is only active when CONFIG_STRICT_DEVMEM is set.
> 
> In addition to the config option, a kernel parameter iomem=relaxed is
> provided for the cases where developers want to diagnose, in the field,
> drivers issues from userspace despite the drivers explicit request.
> 
> Signed-off-by: Arjan van de Ven <arjan@...ux.intel.com>

the concept looks fine to me - the stricter we are in this area the 
better IMO. Unless there are objections, i guess it's best to do this 
via the PCI tree?

	Ingo
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