fbdev: mm: Deferred IO support

This implements deferred IO support in fbdev.  Deferred IO is a way to delay
and repurpose IO.  This implementation is done using mm's page_mkwrite and
page_mkclean hooks in order to detect, delay and then rewrite IO.  This
functionality is used by hecubafb.

[adaplas]
This is useful for graphics hardware with no directly addressable/mappable
framebuffer. Implementing this will allow the "framebuffer" to be accesible
from user space via mmap().

Signed-off-by: Jaya Kumar <jayakumar.lkml@gmail.com>
Signed-off-by: Antonino Daplas <adaplas@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 5 insertions, 0 deletions

diff --git a/drivers/video/Kconfig b/drivers/video/Kconfig
index 8dfa88a68ae9..61c0a03d33f2 100644
--- a/drivers/video/Kconfig
+++ b/drivers/video/Kconfig
@@ -91,6 +91,11 @@ config FB_CFB_IMAGEBLIT
           blitting. This is used by drivers that don't provide their own
           (accelerated) version.
 
+config FB_DEFERRED_IO
+        bool
+        depends on FB
+        default y
+
 config FB_SVGALIB
         tristate
         depends on FB