[PATCH] ARM: allow, but warn, when issuing ioremap() on RAM

Andrew Morton akpm at linux-foundation.org
Fri Oct 8 15:58:03 EDT 2010

On Thu, 7 Oct 2010 20:22:45 +0100
Russell King - ARM Linux <linux at arm.linux.org.uk> wrote:

> On Thu, Oct 07, 2010 at 12:44:22PM +0300, Felipe Contreras wrote:
> > Many drivers are broken, and there's no alternative in sight. Such a big
> > change should stay as a warning for now, and only later should it
> > actually fail.
> > 
> > The drivers are not doing something correct, we get it, but for now it's
> > better to allow them to work (they do 99% of the time anyway) rather
> > than to force everyone to revert this patch in their internal trees
> > until there's a solution. A slightly broken functionality is better than
> > no functionality at all.
> > 
> > A warning lets people know that what they are doing is not right, and
> > they should fix it.
> So what are _you_ going to do to fix these drivers?  Continue reverting
> this patch?  Or are you just going to ignore the issue entirely?
> Unless people can come up with a plan to fix their drivers using ioremap
> on system RAM thereby violating the architecture specification, I'm
> _not_ going to apply this patch.

We *do* have a plan: as of 2.6.36, the kernel will emit a WARN_ON trace
when a driver does this.  Offending code will be discovered, developers
will get bug reports from worried users, etc.  This is usually pretty

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