Allow to set the default loglevel threshold for the console at build time

...And set it to 3, which should only allow to print the messages with
KERN_EMERG, KERN_ALERT and KERN_CRIT levels. This should make the boot
process less noisy.

Can be overridden with loglevel=n boot option.

kernel-i586.config

@@ -7969,6 +7969,7 @@ CONFIG_TRACE_IRQFLAGS_SUPPORT=y
 # printk and dmesg options
 #
 CONFIG_PRINTK_TIME=y
+CONFIG_CONSOLE_LOGLEVEL_DEFAULT=3
 CONFIG_MESSAGE_LOGLEVEL_DEFAULT=4
 CONFIG_BOOT_PRINTK_DELAY=y
 CONFIG_DYNAMIC_DEBUG=y

kernel-x86_64.config

@@ -7790,6 +7790,7 @@ CONFIG_TRACE_IRQFLAGS_SUPPORT=y
 # printk and dmesg options
 #
 CONFIG_PRINTK_TIME=y
+CONFIG_CONSOLE_LOGLEVEL_DEFAULT=3
 CONFIG_MESSAGE_LOGLEVEL_DEFAULT=4
 CONFIG_BOOT_PRINTK_DELAY=y
 CONFIG_DYNAMIC_DEBUG=y

kernel.spec

@@ -216,6 +216,7 @@ Patch200:	i915_hack_bug_97822.patch
 
 # Patches from mainline.
 Patch300:	rt2800-enable-rt3290-unconditionally-on-pci-probe.patch
+Patch301:	printk-add-Kconfig-option-to-set-default-console-loglevel.patch
 
 # Sanitizing kernel memory
 # We do not use "Patch:" here because apply_patches would always apply it

printk-add-Kconfig-option-to-set-default-console-loglevel.patch

@@ -0,0 +1,87 @@
+From a8cfdc68f6cfc0c7ffc6d664406fe7f06f17eef4 Mon Sep 17 00:00:00 2001
+From: Olof Johansson <olof@lixom.net>
+Date: Mon, 12 Dec 2016 16:45:56 -0800
+Subject: [PATCH] printk: add Kconfig option to set default console loglevel
+
+Add a configuration option to set the default console loglevel.  This
+is, as before, still possible to override at runtime through bootargs
+(loglevel=<x>), sysrq and /proc/printk.
+
+There are cases where adding additional arguments on the commandline is
+impractical, and changing the default for the kernel when being built
+makes more sense.  Provide such a method here, for those who choose to
+do so.
+
+Also, while touching this code, clarify the difference between
+MESSAGE_LOGLEVEL_DEFAULT and CONSOLE_LOGLEVEL_DEFAULT.
+
+Link: http://lkml.kernel.org/r/1479676829-30031-1-git-send-email-olof@lixom.net
+Signed-off-by: Olof Johansson <olof@lixom.net>
+Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
+Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
+---
+ include/linux/printk.h |  7 ++++++-
+ lib/Kconfig.debug      | 19 +++++++++++++++++++
+ 2 files changed, 25 insertions(+), 1 deletion(-)
+
+diff --git a/include/linux/printk.h b/include/linux/printk.h
+index afe8cce..3472cc6 100644
+--- a/include/linux/printk.h
++++ b/include/linux/printk.h
+@@ -50,10 +50,15 @@ static inline const char *printk_skip_headers(const char *buffer)
+ #define CONSOLE_LOGLEVEL_SILENT  0 /* Mum's the word */
+ #define CONSOLE_LOGLEVEL_MIN	 1 /* Minimum loglevel we let people use */
+ #define CONSOLE_LOGLEVEL_QUIET	 4 /* Shhh ..., when booted with "quiet" */
+-#define CONSOLE_LOGLEVEL_DEFAULT 7 /* anything MORE serious than KERN_DEBUG */
+ #define CONSOLE_LOGLEVEL_DEBUG	10 /* issue debug messages */
+ #define CONSOLE_LOGLEVEL_MOTORMOUTH 15	/* You can't shut this one up */
+ 
++/*
++ * Default used to be hard-coded at 7, we're now allowing it to be set from
++ * kernel config.
++ */
++#define CONSOLE_LOGLEVEL_DEFAULT CONFIG_CONSOLE_LOGLEVEL_DEFAULT
++
+ extern int console_printk[];
+ 
+ #define console_loglevel (console_printk[0])
+diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
+index 9bb7d82..65a619e 100644
+--- a/lib/Kconfig.debug
++++ b/lib/Kconfig.debug
+@@ -15,6 +15,21 @@ config PRINTK_TIME
+ 	  The behavior is also controlled by the kernel command line
+ 	  parameter printk.time=1. See Documentation/kernel-parameters.txt
+ 
++config CONSOLE_LOGLEVEL_DEFAULT
++	int "Default console loglevel (1-15)"
++	range 1 15
++	default "7"
++	help
++	  Default loglevel to determine what will be printed on the console.
++
++	  Setting a default here is equivalent to passing in loglevel=<x> in
++	  the kernel bootargs. loglevel=<x> continues to override whatever
++	  value is specified here as well.
++
++	  Note: This does not affect the log level of un-prefixed prink()
++	  usage in the kernel. That is controlled by the MESSAGE_LOGLEVEL_DEFAULT
++	  option.
++
+ config MESSAGE_LOGLEVEL_DEFAULT
+ 	int "Default message log level (1-7)"
+ 	range 1 7
+@@ -26,6 +41,10 @@ config MESSAGE_LOGLEVEL_DEFAULT
+ 	  that are auditing their logs closely may want to set it to a lower
+ 	  priority.
+ 
++	  Note: This does not affect what message level gets printed on the console
++	  by default. To change that, use loglevel=<x> in the kernel bootargs,
++	  or pick a different CONSOLE_LOGLEVEL_DEFAULT configuration value.
++
+ config BOOT_PRINTK_DELAY
+ 	bool "Delay each boot printk message by N milliseconds"
+ 	depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY
+-- 
+2.7.3
+