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, 30 insertions, 0 deletions

diff --git a/drivers/video/fbmem.c b/drivers/video/fbmem.c
index 01072f4b3e8f..279c2dbef8f8 100644
--- a/drivers/video/fbmem.c
+++ b/drivers/video/fbmem.c
@@ -1352,6 +1352,32 @@ static const struct file_operations fb_fops = {
 
 struct class *fb_class;
 EXPORT_SYMBOL(fb_class);
+
+static int fb_check_foreignness(struct fb_info *fi)
+{
+        const bool foreign_endian = fi->flags & FBINFO_FOREIGN_ENDIAN;
+
+        fi->flags &= ~FBINFO_FOREIGN_ENDIAN;
+
+#ifdef __BIG_ENDIAN
+        fi->flags |= foreign_endian ? 0 : FBINFO_BE_MATH;
+#else
+        fi->flags |= foreign_endian ? FBINFO_BE_MATH : 0;
+#endif /* __BIG_ENDIAN */
+
+        if (fi->flags & FBINFO_BE_MATH && !fb_be_math(fi)) {
+                pr_err("%s: enable CONFIG_FB_BIG_ENDIAN to "
+                       "support this framebuffer\n", fi->fix.id);
+                return -ENOSYS;
+        } else if (!(fi->flags & FBINFO_BE_MATH) && fb_be_math(fi)) {
+                pr_err("%s: enable CONFIG_FB_LITTLE_ENDIAN to "
+                       "support this framebuffer\n", fi->fix.id);
+                return -ENOSYS;
+        }
+
+        return 0;
+}
+
 /**
  *      register_framebuffer - registers a frame buffer device
  *      @fb_info: frame buffer info structure
@@ -1371,6 +1397,10 @@ register_framebuffer(struct fb_info *fb_info)
 
         if (num_registered_fb == FB_MAX)
                 return -ENXIO;
+
+        if (fb_check_foreignness(fb_info))
+                return -ENOSYS;
+
         num_registered_fb++;
         for (i = 0 ; i < FB_MAX; i++)
                 if (!registered_fb[i])