3 files changed, 40 insertions, 0 deletions

diff --git a/drivers/video/console/fbcon.c b/drivers/video/console/fbcon.c
index b0a3fa00706d..3b3f5749af92 100644
--- a/drivers/video/console/fbcon.c
+++ b/drivers/video/console/fbcon.c
@@ -2342,6 +2342,30 @@ static int fbcon_blank(struct vc_data *vc, int blank, int mode_switch)
         return 0;
 }
 
+static int fbcon_debug_enter(struct vc_data *vc)
+{
+        struct fb_info *info = registered_fb[con2fb_map[vc->vc_num]];
+        struct fbcon_ops *ops = info->fbcon_par;
+
+        ops->save_graphics = ops->graphics;
+        ops->graphics = 0;
+        if (info->fbops->fb_debug_enter)
+                info->fbops->fb_debug_enter(info);
+        fbcon_set_palette(vc, color_table);
+        return 0;
+}
+
+static int fbcon_debug_leave(struct vc_data *vc)
+{
+        struct fb_info *info = registered_fb[con2fb_map[vc->vc_num]];
+        struct fbcon_ops *ops = info->fbcon_par;
+
+        ops->graphics = ops->save_graphics;
+        if (info->fbops->fb_debug_leave)
+                info->fbops->fb_debug_leave(info);
+        return 0;
+}
+
 static int fbcon_get_font(struct vc_data *vc, struct console_font *font)
 {
         u8 *fontdata = vc->vc_font.data;
@@ -3276,6 +3300,8 @@ static const struct consw fb_con = {
         .con_screen_pos         = fbcon_screen_pos,
         .con_getxy              = fbcon_getxy,
         .con_resize             = fbcon_resize,
+        .con_debug_enter        = fbcon_debug_enter,
+        .con_debug_leave        = fbcon_debug_leave,
 };
 
 static struct notifier_block fbcon_event_notifier = {
diff --git a/drivers/video/console/fbcon.h b/drivers/video/console/fbcon.h
index 89a346880ec0..6bd2e0c7f209 100644
--- a/drivers/video/console/fbcon.h
+++ b/drivers/video/console/fbcon.h
@@ -74,6 +74,7 @@ struct fbcon_ops {
         int    cursor_reset;
         int    blank_state;
         int    graphics;
+        int    save_graphics; /* for debug enter/leave */
         int    flags;
         int    rotate;
         int    cur_rotate;
diff --git a/include/linux/fb.h b/include/linux/fb.h
index e7445df44d6c..0c5659c41b01 100644
--- a/include/linux/fb.h
+++ b/include/linux/fb.h
@@ -3,6 +3,9 @@
 
 #include <linux/types.h>
 #include <linux/i2c.h>
+#ifdef __KERNEL__
+#include <linux/kgdb.h>
+#endif /* __KERNEL__ */
 
 /* Definitions of frame buffers                                         */
 
@@ -607,6 +610,12 @@ struct fb_deferred_io {
  * LOCKING NOTE: those functions must _ALL_ be called with the console
  * semaphore held, this is the only suitable locking mechanism we have
  * in 2.6. Some may be called at interrupt time at this point though.
+ *
+ * The exception to this is the debug related hooks.  Putting the fb
+ * into a debug state (e.g. flipping to the kernel console) and restoring
+ * it must be done in a lock-free manner, so low level drivers should
+ * keep track of the initial console (if applicable) and may need to
+ * perform direct, unlocked hardware writes in these hooks.
  */
 
 struct fb_ops {
@@ -676,6 +685,10 @@ struct fb_ops {
 
         /* teardown any resources to do with this framebuffer */
         void (*fb_destroy)(struct fb_info *info);
+
+        /* called at KDB enter and leave time to prepare the console */
+        int (*fb_debug_enter)(struct fb_info *info);
+        int (*fb_debug_leave)(struct fb_info *info);
 };
 
 #ifdef CONFIG_FB_TILEBLITTING