From: John Ogness <john.ogness@linutronix.de>
Date: Mon, 11 Dec 2023 09:36:52 +0000
Subject: [PATCH 26/48] printk: Track nbcon consoles

Add a global flag @have_nbcon_console to identify if any nbcon
consoles are registered. This will be used in follow-up commits
to preserve legacy behavior when no nbcon consoles are registered.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 kernel/printk/printk.c |   14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

Index: linux-6.8.2-rt10/kernel/printk/printk.c
===================================================================
@ linux-6.8.2-rt10/kernel/printk/printk.c:474 @ static DEFINE_MUTEX(syslog_lock);
 static bool have_legacy_console;
 
 /*
+ * Specifies if an nbcon console is registered.
+ */
+static bool have_nbcon_console;
+
+/*
  * Specifies if a boot console is registered. If boot consoles are present,
  * nbcon consoles cannot print simultaneously and must be synchronized by
  * the console lock. This is because boot consoles and nbcon consoles may
@ linux-6.8.2-rt10/kernel/printk/printk.c:3546 @ void register_console(struct console *ne
 	console_init_seq(newcon, bootcon_registered);
 
 	if (newcon->flags & CON_NBCON) {
+		have_nbcon_console = true;
 		nbcon_init(newcon);
 
 		/*
@ linux-6.8.2-rt10/kernel/printk/printk.c:3633 @ EXPORT_SYMBOL(register_console);
 static int unregister_console_locked(struct console *console)
 {
 	bool found_legacy_con = false;
+	bool found_nbcon_con = false;
 	bool found_boot_con = false;
 	struct console *c;
 	int res;
@ linux-6.8.2-rt10/kernel/printk/printk.c:3690 @ static int unregister_console_locked(str
 	for_each_console(c) {
 		if (c->flags & CON_BOOT)
 			found_boot_con = true;
-		if (!(c->flags & CON_NBCON))
+
+		if (c->flags & CON_NBCON)
+			found_nbcon_con = true;
+		else
 			found_legacy_con = true;
 	}
 	if (!found_boot_con)
 		have_boot_console = found_boot_con;
 	if (!found_legacy_con)
 		have_legacy_console = found_legacy_con;
+	if (!found_nbcon_con)
+		have_nbcon_console = found_nbcon_con;
 
 	return res;
 }