Re: [PATCH] driver core: simplify platform_get_resource()

Greg KH
2009-07-28T16:33:19Z

On Tue, Jul 28, 2009 at 11:59:49AM +0100, Mark Brown wrote:
> On Mon, Jul 27, 2009 at 02:20:56PM -0400, Mike Frysinger wrote:
> > The platform_get_resource() function takes a number for the desired index
> > into the resource array, but then does a for loop on the array to get to
> > that index. Considering the array is linear, the loop overhead is just
> > that -- overhead. So unless I missed something, convert it into an index
> > check and access the desired resource directly. Resulting code makes a
> > lot more sense considering its purpose.
>
> This showed up in linux-next for me today and is causing breakage on at
> least S3C64xx platforms since it changes the resource numbering when
> there's more than one resource type for a device:
>
> > - for (i = 0; i < dev->num_resources; i++) {
> > - struct resource *r = &dev->resource[i];
> > -
> > - if (type == resource_type(r) && num-- == 0)
> > + if (num >= 0 && num < dev->num_resources) {
> > + struct resource *r = &dev->resource[num];
> > + if (type == resource_type(r))
>
> Previously the resources were indexed within their type (so you'd get
> I/O resources 0, 1, ..., IRQ resources 0, 1, ... and so on) but now the
> index treats all the resources for a device as a single array, causing
> them to be renumbered for callers.
>
> This causes drivers doing lookups by number to fail to find their
> resources and not probe, causing widespread breakage. Reverting the
> patch fixes the problem.

I've now dropped this patch.

thanks,

greg k-h