x86/mm/mtrr: Avoid #ifdeffery with phys_wc_to_mtrr_index()

There is only one user but since we're going to bury MTRR next
out of access to drivers, expose this last piece of API to
drivers in a general fashion only needing io.h for access to
helpers.

Signed-off-by: Luis R. Rodriguez <[e-mail]>
Signed-off-by: Borislav Petkov <[e-mail]>
Cc: Abhilash Kesavan <[e-mail]>
Cc: Andrew Morton <[e-mail]>
Cc: Andy Lutomirski <[e-mail]>
Cc: Antonino Daplas <[e-mail]>
Cc: Borislav Petkov <[e-mail]>
Cc: Brian Gerst <[e-mail]>
Cc: Catalin Marinas <[e-mail]>
Cc: Cristian Stoica <[e-mail]>
Cc: Daniel Vetter <[e-mail]>
Cc: Dave Airlie <[e-mail]>
Cc: Dave Hansen <[e-mail]>
Cc: Davidlohr Bueso <[e-mail]>
Cc: Denys Vlasenko <[e-mail]>
Cc: Greg Kroah-Hartman <[e-mail]>
Cc: H. Peter Anvin <[e-mail]>
Cc: Jean-Christophe Plagniol-Villard <[e-mail]>
Cc: Juergen Gross <[e-mail]>
Cc: Linus Torvalds <[e-mail]>
Cc: Matthias Brugger <[e-mail]>
Cc: Mel Gorman <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Suresh Siddha <[e-mail]>
Cc: Thierry Reding <[e-mail]>
Cc: Thomas Gleixner <[e-mail]>
Cc: Tomi Valkeinen <[e-mail]>
Cc: Toshi Kani <[e-mail]>
Cc: Ville Syrjälä <[e-mail]>
Cc: Vlastimil Babka <[e-mail]>
Cc: Will Deacon <[e-mail]>
Cc: [e-mail]
Link: http://lkml.kernel.org/r/[e-mail]
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Ingo Molnar <[e-mail]>

arch/x86/include/asm/io.h

···
 #define IO_SPACE_LIMIT 0xffff
 
 #ifdef CONFIG_MTRR
+extern int __must_check arch_phys_wc_index(int handle);
+#define arch_phys_wc_index arch_phys_wc_index
+
 extern int __must_check arch_phys_wc_add(unsigned long base,
 					 unsigned long size);
 extern void arch_phys_wc_del(int handle);

arch/x86/include/asm/mtrr.h

···
 extern void mtrr_bp_restore(void);
 extern int mtrr_trim_uncached_memory(unsigned long end_pfn);
 extern int amd_special_default_mtrr(void);
-extern int phys_wc_to_mtrr_index(int handle);
 #  else
 static inline u8 mtrr_type_lookup(u64 addr, u64 end, u8 *uniform)
 {
···
 }
 static inline void mtrr_centaur_report_mcr(int mcr, u32 lo, u32 hi)
 {
-}
-static inline int phys_wc_to_mtrr_index(int handle)
-{
-	return -1;
 }
 
 #define mtrr_ap_init() do {} while (0)

arch/x86/kernel/cpu/mtrr/main.c

···
 EXPORT_SYMBOL(arch_phys_wc_del);
 
 /*
- * phys_wc_to_mtrr_index - translates arch_phys_wc_add's return value
+ * arch_phys_wc_index - translates arch_phys_wc_add's return value
  * @handle: Return value from arch_phys_wc_add
  *
  * This will turn the return value from arch_phys_wc_add into an mtrr
···
  * in printk line.  Alas there is an illegitimate use in some ancient
  * drm ioctls.
  */
-int phys_wc_to_mtrr_index(int handle)
+int arch_phys_wc_index(int handle)
 {
 	if (handle < MTRR_TO_PHYS_WC_OFFSET)
 		return -1;
 	else
 		return handle - MTRR_TO_PHYS_WC_OFFSET;
 }
-EXPORT_SYMBOL_GPL(phys_wc_to_mtrr_index);
+EXPORT_SYMBOL_GPL(arch_phys_wc_index);
 
 /*
  * HACK ALERT!

drivers/gpu/drm/drm_ioctl.c

···
 
 #include <linux/pci.h>
 #include <linux/export.h>
-#ifdef CONFIG_X86
-#include <asm/mtrr.h>
-#endif
 
 static int drm_version(struct drm_device *dev, void *data,
 		       struct drm_file *file_priv);
···
 	map->type = r_list->map->type;
 	map->flags = r_list->map->flags;
 	map->handle = (void *)(unsigned long) r_list->user_token;
-
-#ifdef CONFIG_X86
-	/*
-	 * There appears to be exactly one user of the mtrr index: dritest.
-	 * It's easy enough to keep it working on non-PAT systems.
-	 */
-	map->mtrr = phys_wc_to_mtrr_index(r_list->map->mtrr);
-#else
-	map->mtrr = -1;
-#endif
+	map->mtrr = arch_phys_wc_index(r_list->map->mtrr);
 
 	mutex_unlock(&dev->struct_mutex);
 

include/linux/io.h

···
 }
 
 #define arch_phys_wc_add arch_phys_wc_add
+#ifndef arch_phys_wc_index
+static inline int arch_phys_wc_index(int handle)
+{
+	return -1;
+}
+#define arch_phys_wc_index arch_phys_wc_index
+#endif
 #endif
 
 #endif /* _LINUX_IO_H */