fbcon: move more common code into fb_open()

No idea why con2fb_acquire_newinfo() initializes much less than
fbcon_startup(), but so be it. From a quick look most of the
un-initialized stuff should be fairly harmless, but who knows.

Note that the error handling for the con2fb_acquire_newinfo() failure
case was very strange: Callers updated con2fb_map to the new value
before calling this function, but upon error con2fb_acquire_newinfo
reset it to the old value. Since I removed the call to fbcon_release
anyway that strange error path was sticking out like a sore thumb,
hence I removed it. Which also allows us to remove the oldidx
parameter from that function.

v2: Explain what's going on with oldidx and error paths (Sam)

v3: Drop unused variable (0day)

v4: Rebased over bisect fix in previous patch, unchagend end result.

Acked-by: Sam Ravnborg <sam@ravnborg.org> (v2)
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Cc: kernel test robot <lkp@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Claudio Suarez <cssk@net-c.es>
Cc: Du Cheng <ducheng2@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220405210335.3434130-12-daniel.vetter@ffwll.ch

drivers/video/fbdev/core/fbcon.c

@@ -682,8 +682,18 @@ static int fbcon_invalid_charcount(struct fb_info *info, unsigned charcount)
 
 #endif /* CONFIG_MISC_TILEBLITTING */
 
+static void fbcon_release(struct fb_info *info)
+{
+	if (info->fbops->fb_release)
+		info->fbops->fb_release(info, 0);
+
+	module_put(info->fbops->owner);
+}
+
 static int fbcon_open(struct fb_info *info)
 {
+	struct fbcon_ops *ops;
+
 	if (!try_module_get(info->fbops->owner))
 		return -ENODEV;
 
@@ -693,48 +703,31 @@ static int fbcon_open(struct fb_info *info)
 		return -ENODEV;
 	}
 
-	return 0;
-}
+	ops = kzalloc(sizeof(struct fbcon_ops), GFP_KERNEL);
+	if (!ops) {
+		fbcon_release(info);
+		return -ENOMEM;
+	}
 
-static void fbcon_release(struct fb_info *info)
-{
-	if (info->fbops->fb_release)
-		info->fbops->fb_release(info, 0);
+	INIT_DELAYED_WORK(&ops->cursor_work, fb_flashcursor);
+	ops->info = info;
+	info->fbcon_par = ops;
+	ops->cur_blink_jiffies = HZ / 5;
 
-	module_put(info->fbops->owner);
+	return 0;
 }
 
 static int con2fb_acquire_newinfo(struct vc_data *vc, struct fb_info *info,
-				  int unit, int oldidx)
+				  int unit)
 {
-	struct fbcon_ops *ops = NULL;
 	int err;
 
 	err = fbcon_open(info);
 	if (err)
 		return err;
 
-	if (!err) {
-		ops = kzalloc(sizeof(struct fbcon_ops), GFP_KERNEL);
-		if (!ops)
-			err = -ENOMEM;
-	}
-
-	if (!err) {
-		INIT_DELAYED_WORK(&ops->cursor_work, fb_flashcursor);
-
-		ops->cur_blink_jiffies = HZ / 5;
-		ops->info = info;
-		info->fbcon_par = ops;
-
 	if (vc)
 		set_blitting_type(vc, info);
-	}
-
-	if (err) {
-		con2fb_map[unit] = oldidx;
-		fbcon_release(info);
-	}
 
 	return err;
 }
@@ -842,9 +835,11 @@ static int set_con2fb_map(int unit, int newidx, int user)
 
 	found = search_fb_in_map(newidx);
 
+	if (!err && !found) {
+		err = con2fb_acquire_newinfo(vc, info, unit);
+		if (!err)
 			con2fb_map[unit] = newidx;
-	if (!err && !found)
-		err = con2fb_acquire_newinfo(vc, info, unit, oldidx);
+	}
 
 	/*
 	 * If old fb is not mapped to any of the consoles,
@@ -941,20 +936,10 @@ static const char *fbcon_startup(void)
 	if (fbcon_open(info))
 		return NULL;
 
-	ops = kzalloc(sizeof(struct fbcon_ops), GFP_KERNEL);
-	if (!ops) {
-		fbcon_release(info);
-		return NULL;
-	}
-
-	INIT_DELAYED_WORK(&ops->cursor_work, fb_flashcursor);
-
+	ops = info->fbcon_par;
 	ops->currcon = -1;
 	ops->graphics = 1;
 	ops->cur_rotate = -1;
-	ops->cur_blink_jiffies = HZ / 5;
-	ops->info = info;
-	info->fbcon_par = ops;
 
 	p->con_rotate = initial_rotation;
 	if (p->con_rotate == -1)
@@ -1024,7 +1009,7 @@ static void fbcon_init(struct vc_data *vc, int init)
 		return;
 
 	if (!info->fbcon_par)
-		con2fb_acquire_newinfo(vc, info, vc->vc_num, -1);
+		con2fb_acquire_newinfo(vc, info, vc->vc_num);
 
 	/* If we are not the first console on this
 	   fb, copy the font from that console */