add printk.time option, deprecate 'time'

Allow printk_time to be enabled or disabled at boot time. Previously it
could be enabled only, but not disabled.

Change printk_time from an int to a bool since that's what it is. Make its
logical (exposed) name just be "time" (was "printk_time").

Note: Changes kernel boot option syntax from "time" to "printk.time=value".

Since printk_time is declared as a module_param, it can also be
changed at run-time by modifying
/sys/module/printk/parameters/time
to a value of 1/Y/y to enabled it or 0/N/n to disable it.

Since printk_time is declared as a module_param, its value can also
be set at boot-time by using
linux printk.time=<bool>

If the "time" boot option is used, print a message that it is deprecated
and will be removed.

Note its planned removal in feature-removal-schedule.txt.

Signed-off-by: Randy Dunlap <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

Documentation/feature-removal-schedule.txt

···
 
 ---------------------------
 
+What:	'time' kernel boot parameter
+When:	January 2008
+Why:	replaced by 'printk.time=<value>' so that printk timestamps can be
+	enabled or disabled as needed
+Who:	Randy Dunlap <[e-mail]>
+
+---------------------------
+
 What:  drivers depending on OSS_OBSOLETE
 When:  options in 2.6.23, code in 2.6.25
 Why:   obsolete OSS drivers

Documentation/kernel-parameters.txt

···
 			the kernel console.
 			default: off.
 
+	printk.time=	Show timing data prefixed to each printk message line
+			Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
+
 	profile=	[KNL] Enable kernel profiling via /proc/profile
 			Format: [schedule,]<number>
 			Param: "schedule" - profile schedule points.
···
 			Set number of hash buckets for TCP connection
 
 	time		Show timing data prefixed to each printk message line
+			[deprecated, see 'printk.time']
 
 	tipar.timeout=	[HW,PPT]
 			Set communications timeout in tenths of a second

kernel/printk.c

···
 #else
 static int printk_time = 0;
 #endif
-module_param(printk_time, int, S_IRUGO | S_IWUSR);
+module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
 
 static int __init printk_time_setup(char *str)
 {
 	if (*str)
 		return 0;
 	printk_time = 1;
+	printk(KERN_NOTICE "The 'time' option is deprecated and "
+		"is scheduled for removal in early 2008\n");
+	printk(KERN_NOTICE "Use 'printk.time=<value>' instead\n");
 	return 1;
 }