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>

2 files changed, 93 insertions, 7 deletions

diff --git a/drivers/video/console/Kconfig b/drivers/video/console/Kconfig
index d3b8a6be2916..160f55f7ac96 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
diff --git a/drivers/video/console/fbcon.c b/drivers/video/console/fbcon.c
index 7f4ed792307c..7ba21eb1676c 100644
--- a/drivers/video/console/fbcon.c
+++ b/drivers/video/console/fbcon.c
@@ -75,6 +75,7 @@
 #include <linux/init.h>
 #include <linux/interrupt.h>
 #include <linux/crc32.h> /* For counting font checksums */
+#include <asm/fb.h>
 #include <asm/irq.h>
 #include <asm/system.h>
 #include <asm/uaccess.h>
@@ -125,6 +126,8 @@ static int first_fb_vc;
 static int last_fb_vc = MAX_NR_CONSOLES - 1;
 static int fbcon_is_default = 1; 
 static int fbcon_has_exited;
+static int primary_device = -1;
+static int map_override;
 
 /* font data */
 static char fontname[40];
@@ -497,13 +500,17 @@ static int __init fb_console_setup(char *this_opt)
                 
                 if (!strncmp(options, "map:", 4)) {
                         options += 4;
-                        if (*options)
+                        if (*options) {
                                 for (i = 0, j = 0; i < MAX_NR_CONSOLES; i++) {
                                         if (!options[j])
                                                 j = 0;
                                         con2fb_map_boot[i] =
                                                 (options[j++]-'0') % FB_MAX;
                                 }
+
+                                map_override = 1;
+                        }
+
                         return 1;
                 }
 
@@ -3004,9 +3011,9 @@ static int fbcon_mode_deleted(struct fb_info *info,
         return found;
 }
 
-static int fbcon_fb_unregistered(int idx)
+static int fbcon_fb_unregistered(struct fb_info *info)
 {
-        int i;
+        int i, idx = info->node;
 
         for (i = first_fb_vc; i <= last_fb_vc; i++) {
                 if (con2fb_map[i] == idx)
@@ -3034,12 +3041,70 @@ static int fbcon_fb_unregistered(int idx)
         if (!num_registered_fb)
                 unregister_con_driver(&fb_con);
 
+
+        if (primary_device == idx)
+                primary_device = -1;
+
+        return 0;
+}
+
+#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DETECT_PRIMARY
+static int fbcon_select_primary(struct fb_info *info)
+{
+        int ret = 0;
+
+        if (!map_override && primary_device == -1 &&
+            fb_is_primary_device(info)) {
+                int i, err;
+
+                printk(KERN_INFO "fbcon: %s is primary device\n",
+                       info->fix.id);
+                primary_device = info->node;
+
+                if (!con_is_bound(&fb_con))
+                        goto done;
+
+                printk(KERN_INFO "fbcon: Unbinding old driver\n");
+                unbind_con_driver(&fb_con, first_fb_vc, last_fb_vc,
+                                  fbcon_is_default);
+                info_idx = primary_device;
+
+                for (i = first_fb_vc; i <= last_fb_vc; i++) {
+                        con2fb_map_boot[i] = primary_device;
+                        con2fb_map[i] = primary_device;
+                }
+
+                printk(KERN_INFO "fbcon: Selecting new driver\n");
+                err = bind_con_driver(&fb_con, first_fb_vc, last_fb_vc,
+                                      fbcon_is_default);
+
+                if (err) {
+                        for (i = first_fb_vc; i <= last_fb_vc; i++)
+                                con2fb_map[i] = -1;
+
+                        info_idx = -1;
+                }
+
+                ret = 1;
+        }
+
+done:
+        return ret;
+}
+#else
+static inline int fbcon_select_primary(struct fb_info *info)
+{
         return 0;
 }
+#endif /* CONFIG_FRAMEBUFFER_DETECT_PRIMARY */
 
-static int fbcon_fb_registered(int idx)
+static int fbcon_fb_registered(struct fb_info *info)
 {
-        int ret = 0, i;
+        int ret = 0, i, idx = info->node;
+
+        if (fbcon_select_primary(info))
+                goto done;
+
 
         if (info_idx == -1) {
                 for (i = first_fb_vc; i <= last_fb_vc; i++) {
@@ -3059,6 +3124,7 @@ static int fbcon_fb_registered(int idx)
                 }
         }
 
+done:
         return ret;
 }
 
@@ -3182,10 +3248,10 @@ static int fbcon_event_notify(struct notifier_block *self,
                 ret = fbcon_mode_deleted(info, mode);
                 break;
         case FB_EVENT_FB_REGISTERED:
-                ret = fbcon_fb_registered(info->node);
+                ret = fbcon_fb_registered(info);
                 break;
         case FB_EVENT_FB_UNREGISTERED:
-                ret = fbcon_fb_unregistered(info->node);
+                ret = fbcon_fb_unregistered(info);
                 break;
         case FB_EVENT_SET_CONSOLE_MAP:
                 con2fb = event->data;