fb: add support for foreign endianness

Add support for the framebuffers with non-native endianness.  This is done via
FBINFO_FOREIGN_ENDIAN flag that will be used by the drivers.  Depending on the
host endianness this flag will be overwritten by FBINFO_BE_MATH internal flag,
or cleared.

Tested to work on MPC8360E-RDK (BE) + Fujitsu MINT framebuffer (LE).

Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
Cc: "Antonino A. Daplas" <adaplas@pol.net>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: <Valdis.Kletnieks@vt.edu>
Cc: Clemens Koller <clemens.koller@anagramm.de>
Cc: Krzysztof Helt <krzysztof.h1@poczta.fm>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 35 insertions, 9 deletions

diff --git a/include/linux/fb.h b/include/linux/fb.h
index 58c57a33e5dd..72295b099228 100644
--- a/include/linux/fb.h
+++ b/include/linux/fb.h
@@ -791,6 +791,17 @@ struct fb_tile_ops {
  */
 #define FBINFO_MISC_ALWAYS_SETPAR   0x40000
 
+/*
+ * Host and GPU endianness differ.
+ */
+#define FBINFO_FOREIGN_ENDIAN   0x100000
+/*
+ * Big endian math. This is the same flags as above, but with different
+ * meaning, it is set by the fb subsystem depending FOREIGN_ENDIAN flag
+ * and host endianness. Drivers should not use this flag.
+ */
+#define FBINFO_BE_MATH  0x100000
+
 struct fb_info {
         int node;
         int flags;
@@ -899,15 +910,11 @@ struct fb_info {
 
 #endif
 
-#if defined (__BIG_ENDIAN)
-#define FB_LEFT_POS(bpp)          (32 - bpp)
-#define FB_SHIFT_HIGH(val, bits)  ((val) >> (bits))
-#define FB_SHIFT_LOW(val, bits)   ((val) << (bits))
-#else
-#define FB_LEFT_POS(bpp)          (0)
-#define FB_SHIFT_HIGH(val, bits)  ((val) << (bits))
-#define FB_SHIFT_LOW(val, bits)   ((val) >> (bits))
-#endif
+#define FB_LEFT_POS(p, bpp)          (fb_be_math(p) ? (32 - (bpp)) : 0)
+#define FB_SHIFT_HIGH(p, val, bits)  (fb_be_math(p) ? (val) >> (bits) : \
+                                                      (val) << (bits))
+#define FB_SHIFT_LOW(p, val, bits)   (fb_be_math(p) ? (val) << (bits) : \
+                                                      (val) >> (bits))
 
     /*
      *  `Generic' versions of the frame buffer device operations
@@ -970,6 +977,25 @@ extern void fb_deferred_io_cleanup(struct fb_info *info);
 extern int fb_deferred_io_fsync(struct file *file, struct dentry *dentry,
                                 int datasync);
 
+static inline bool fb_be_math(struct fb_info *info)
+{
+#ifdef CONFIG_FB_FOREIGN_ENDIAN
+#if defined(CONFIG_FB_BOTH_ENDIAN)
+        return info->flags & FBINFO_BE_MATH;
+#elif defined(CONFIG_FB_BIG_ENDIAN)
+        return true;
+#elif defined(CONFIG_FB_LITTLE_ENDIAN)
+        return false;
+#endif /* CONFIG_FB_BOTH_ENDIAN */
+#else
+#ifdef __BIG_ENDIAN
+        return true;
+#else
+        return false;
+#endif /* __BIG_ENDIAN */
+#endif /* CONFIG_FB_FOREIGN_ENDIAN */
+}
+
 /* drivers/video/fbsysfs.c */
 extern struct fb_info *framebuffer_alloc(size_t size, struct device *dev);
 extern void framebuffer_release(struct fb_info *info);