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, 20 insertions, 0 deletions

diff --git a/include/linux/fb.h b/include/linux/fb.h
index be913ec87169..8a8255b94b62 100644
--- a/include/linux/fb.h
+++ b/include/linux/fb.h
@@ -561,6 +561,16 @@ struct fb_pixmap {
         void (*readio) (struct fb_info *info, void *dst, void __iomem *src, unsigned int size);
 };
 
+#ifdef CONFIG_FB_DEFERRED_IO
+struct fb_deferred_io {
+        /* delay between mkwrite and deferred handler */
+        unsigned long delay;
+        struct mutex lock; /* mutex that protects the page list */
+        struct list_head pagelist; /* list of touched pages */
+        /* callback */
+        void (*deferred_io)(struct fb_info *info, struct list_head *pagelist);
+};
+#endif
 
 /*
  * Frame buffer operations
@@ -778,6 +788,10 @@ struct fb_info {
         struct mutex bl_curve_mutex;    
         u8 bl_curve[FB_BACKLIGHT_LEVELS];
 #endif
+#ifdef CONFIG_FB_DEFERRED_IO
+        struct delayed_work deferred_work;
+        struct fb_deferred_io *fbdefio;
+#endif
 
         struct fb_ops *fbops;
         struct device *device;          /* This is the parent */
@@ -913,6 +927,12 @@ static inline void __fb_pad_aligned_buffer(u8 *dst, u32 d_pitch,
         }
 }
 
+#ifdef CONFIG_FB_DEFERRED_IO
+/* drivers/video/fb_defio.c */
+extern void fb_deferred_io_init(struct fb_info *info);
+extern void fb_deferred_io_cleanup(struct fb_info *info);
+#endif
+
 /* drivers/video/fbsysfs.c */
 extern struct fb_info *framebuffer_alloc(size_t size, struct device *dev);
 extern void framebuffer_release(struct fb_info *info);