fbcon: set_con2fb_map fixes

set_con2fb_map() has regressed for some time.  Using fbcon=map:01, for
example, works only if there is only 1 working framebuffer. Trying to do a
set_con2fb_map() on a non-allocated vc will freeze the system.

- ensure that succeeding drivers after the first gets mapped to the console
- remove fbcon_preset_display() and modify fbcon_set_display() to include the
  former's functionality
- ensure that binding and unbinding succeeds if multiple drivers are mapped to
  the console
Signed-off-by: NAntonino Daplas <adaplas@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/video/console/fbcon.c

@@ -192,9 +192,7 @@ static __inline__ void ypan_down(struct vc_data *vc, int count);
 static void fbcon_bmove_rec(struct vc_data *vc, struct display *p, int sy, int sx,
 			    int dy, int dx, int height, int width, u_int y_break);
 static void fbcon_set_disp(struct fb_info *info, struct fb_var_screeninfo *var,
-			   struct vc_data *vc);
-static void fbcon_preset_disp(struct fb_info *info, struct fb_var_screeninfo *var,
-			      int unit);
+			   int unit);
 static void fbcon_redraw_move(struct vc_data *vc, struct display *p,
 			      int line, int count, int dy);
 static void fbcon_modechanged(struct fb_info *info);
@@ -745,7 +743,9 @@ static int con2fb_acquire_newinfo(struct vc_data *vc, struct fb_info *info,
 
 	if (!err) {
 		info->fbcon_par = ops;
-		set_blitting_type(vc, info);
+
+		if (vc)
+			set_blitting_type(vc, info);
 	}
 
 	if (err) {
@@ -807,11 +807,7 @@ static void con2fb_init_display(struct vc_data *vc, struct fb_info *info,
 
 	ops->flags |= FBCON_FLAGS_INIT;
 	ops->graphics = 0;
-
-	if (vc)
-		fbcon_set_disp(info, &info->var, vc);
-	else
-		fbcon_preset_disp(info, &info->var, unit);
+	fbcon_set_disp(info, &info->var, unit);
 
 	if (show_logo) {
 		struct vc_data *fg_vc = vc_cons[fg_console].d;
@@ -1116,6 +1112,9 @@ static void fbcon_init(struct vc_data *vc, int init)
 	if (var_to_display(p, &info->var, info))
 		return;
 
+	if (!info->fbcon_par)
+		con2fb_acquire_newinfo(vc, info, vc->vc_num, -1);
+
 	/* If we are not the first console on this
 	   fb, copy the font from that console */
 	t = &fb_display[fg_console];
@@ -1382,36 +1381,29 @@ static int scrollback_phys_max = 0;
 static int scrollback_max = 0;
 static int scrollback_current = 0;
 
-/*
- * If no vc is existent yet, just set struct display
- */
-static void fbcon_preset_disp(struct fb_info *info, struct fb_var_screeninfo *var,
-			      int unit)
-{
-	struct display *p = &fb_display[unit];
-	struct display *t = &fb_display[fg_console];
-
-	if (var_to_display(p, var, info))
-		return;
-
-	p->fontdata = t->fontdata;
-	p->userfont = t->userfont;
-	if (p->userfont)
-		REFCOUNT(p->fontdata)++;
-}
-
 static void fbcon_set_disp(struct fb_info *info, struct fb_var_screeninfo *var,
-			   struct vc_data *vc)
+			   int unit)
 {
-	struct display *p = &fb_display[vc->vc_num], *t;
-	struct vc_data **default_mode = vc->vc_display_fg;
-	struct vc_data *svc = *default_mode;
+	struct display *p, *t;
+	struct vc_data **default_mode, *vc;
+	struct vc_data *svc;
 	struct fbcon_ops *ops = info->fbcon_par;
 	int rows, cols, charcnt = 256;
 
+	p = &fb_display[unit];
+
 	if (var_to_display(p, var, info))
 		return;
+
+	vc = vc_cons[unit].d;
+
+	if (!vc)
+		return;
+
+	default_mode = vc->vc_display_fg;
+	svc = *default_mode;
 	t = &fb_display[svc->vc_num];
+
 	if (!vc->vc_font.data) {
 		vc->vc_font.data = (void *)(p->fontdata = t->fontdata);
 		vc->vc_font.width = (*default_mode)->vc_font.width;
@@ -3118,8 +3110,7 @@ static int fbcon_fb_registered(struct fb_info *info)
 			ret = fbcon_takeover(1);
 	} else {
 		for (i = first_fb_vc; i <= last_fb_vc; i++) {
-			if (con2fb_map_boot[i] == idx &&
-			    con2fb_map[i] == -1)
+			if (con2fb_map_boot[i] == idx)
 				set_con2fb_map(i, idx, 0);
 		}
 	}
@@ -3167,12 +3158,7 @@ static void fbcon_new_modelist(struct fb_info *info)
 		mode = fb_find_nearest_mode(fb_display[i].mode,
 					    &info->modelist);
 		fb_videomode_to_var(&var, mode);
-
-		if (vc)
-			fbcon_set_disp(info, &var, vc);
-		else
-			fbcon_preset_disp(info, &var, i);
-
+		fbcon_set_disp(info, &var, vc->vc_num);
 	}
 }