fbcon: allow fbcon to use the primary display driver

Allow fbcon to select the primary display adapter using the
fb_is_primary_device() arch-specific helper.  If a a primary adapter is
detected, fbcon will unbind the old adapter from the VT layer, then rebind
using the new adapter.  This requires that bind_/unbind_con_driver() be made
public.

Because this feature may produce unexpected behavior (from the user's POV),
this must be explicitly enabled in Kconfig.

[akpm@linux-foundation.org: export unbind_con_driver]
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/drivers/video/console/Kconfig b/drivers/video/console/Kconfig
index d3b8a6b..160f55f 100644
--- a/drivers/video/console/Kconfig
+++ b/drivers/video/console/Kconfig
@@ -118,6 +118,26 @@ config FRAMEBUFFER_CONSOLE
 	help
 	  Low-level framebuffer-based console driver.
 
+config FRAMEBUFFER_CONSOLE_DETECT_PRIMARY
+       bool "Map the console to the primary display device"
+       depends on FRAMEBUFFER_CONSOLE && VT_HW_CONSOLE_BINDING
+       default n
+       ---help---
+         If this option is selected, the framebuffer console will
+         automatically select the primary display device (if the architecture
+	 supports this feature).  Otherwise, the framebuffer console will
+         always select the first framebuffer driver that is loaded. The latter
+         is the default behavior.
+
+	 You can always override the automatic selection of the primary device
+	 by using the fbcon=map: boot option.
+
+	 To select this feature, "Support for binding and unbinding console
+         drivers", under "Device Drivers"->"Character Devices" must be set to
+	 y.
+
+	 If unsure, select n.
+
 config FRAMEBUFFER_CONSOLE_ROTATION
        bool "Framebuffer Console Rotation"
        depends on FRAMEBUFFER_CONSOLE