Re: [PATCH 01/11] Add generic fixmap.h

On Tuesday 12 November 2013, Mark Salter wrote:

Many architectures provide an asm/fixmap.h which defines support for
compile-time 'special' virtual mappings which need to be made before
paging_init() has run. This suport is also used for early ioremap
on x86. Much of this support is identical across the architectures.
This patch consolidates all of the common bits into asm-generic/fixmap.h
which is intended to be included from arch/*/include/asm/fixmap.h.

Good idea, 

Acked-by: Arnd Bergmann <arnd@arndb.de>

On Tuesday 12 November 2013, Mark Salter wrote:

+static __always_inline unsigned long fix_to_virt(const unsigned int idx)
+{
+       /*
+        * this branch gets completely eliminated after inlining,
+        * except when someone tries to use fixaddr indices in an
+        * illegal way. (such as mixing up address types or using
+        * out-of-range indices).
+        *
+        * If it doesn't get removed, the linker will complain
+        * loudly with a reasonably clear error message..
+        */
+       if (idx >= __end_of_fixed_addresses)
+               __this_fixmap_does_not_exist();
+

You might be able to turn this into the more readable BUILD_BUG_ON().

	Arnd