linux-kernel - [PATCH] console: don't select first registered console if stdout-path used

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Date:   Fri, 25 Aug 2017 16:14:51 +0300
From:   Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>
To:     Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        linux-snps-arc@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>
Subject: [PATCH] console: don't select first registered console if stdout-path used

In the current implementation we take the first console that
registers if we didn't select one.

But if we specify console via "stdout-path" property in device tree
we don't want first console that registers here to be selected.
Otherwise we may choose wrong console - for example if some console
is registered earlier than console is pointed in "stdout-path"
property because console pointed in "stdout-path" property can be add as
preferred quite late - when it's driver is probed.

Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>
---
 kernel/printk/printk.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 512f7c2..23262c1 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -26,6 +26,7 @@
 #include <linux/nmi.h>
 #include <linux/module.h>
 #include <linux/moduleparam.h>
+#include <linux/of.h>
 #include <linux/delay.h>
 #include <linux/smp.h>
 #include <linux/security.h>
@@ -2431,6 +2432,16 @@ void register_console(struct console *newcon)
 	if (!has_preferred || bcon || !console_drivers)
 		has_preferred = preferred_console >= 0;
 
+
+	/*
+	 * If we specify console via "stdout-path" property in device tree
+	 * we don't want first console that registers here to be selected.
+	 */
+#ifdef CONFIG_OF
+	if (of_stdout)
+		has_preferred = true;
+#endif
+
 	/*
 	 *	See if we want to use this console driver. If we
 	 *	didn't select a console we take the first one
-- 
2.9.3