[RFC] expand_resource()

[Matthew Wilcox <willy@debian.org>]

We have a situation where we descend through the resource tree and
figure out that firmware has set up the resources wrongly.  This patch
allows us to grow our parent's resource to accommodate our requirements.

I'm looking for feedback at this point, not application, so I've mangled
the patch to make it hard to apply.

diff -u -p -r1.2 resource.c
--- kernel/resource.c   12 Aug 2003 19:11:29 -0000      1.2
+++ kernel/resource.c   26 Sep 2003 02:28:45 -0000
@@ -250,6 +252,62 @@ int allocate_resource(struct resource *r
                err = -EBUSY;
        write_unlock(&resource_lock);
        return err;
+}
+
+/*
+ * Expand an existing resource by size amount.
+ */
+int expand_resource(struct resource *res, unsigned long size,
+                          unsigned long align)
+{
+       unsigned long start, end;
+
+       /* see if we can expand above */
+       end = (res->end + size + align - 1) & ~(align - 1);
+
+       write_lock(&resource_lock);
+       if (res->sibling) {
+               if (res->sibling->start > end)
+                       goto end;
+       } else {
+               if (res->parent->end >= end)
+                       goto end;
+       }
+
+       /* now try below */
+       start = ((res->start - size + align) & ~(align - 1)) - align;
+
+       if (res->parent->child == res) {
+               if (res->start <= start)
+                       goto start;
+       } else {
+               struct resource *prev = res->parent->child;
+               while (prev->sibling != res)
+                       prev = prev->sibling;
+               if (prev->end < start)
+                       goto start;
+       }
+
+       write_unlock(&resource_lock);
+       return -ENOMEM;
+
+ start:
+       res->start = start;
+       write_unlock(&resource_lock);
+       return 0;
+ end:
+       res->end = end;
+       write_unlock(&resource_lock);
+       return 0;
 }


-- 
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