Re-enable CTL in GENERIC on i386 and amd64, but turn on the CTL disable

tunable by default.

This will allow GENERIC configurations to boot on small memory boxes, but
not require end users who want to use CTL to recompile their kernel.  They
can simply set kern.cam.ctl.disable=0 in loader.conf.

The eventual solution to the memory usage problem is to change the way
CTL allocates memory to be more configurable, but this should fix things
for small memory situations in the mean time.

UPDATING:		Explain the change in the CTL configuration, and
			how users can enable CTL if they would like to use
			it.

sys/conf/options:	Add a new option, CTL_DISABLE, that prevents CTL
			from initializing.

ctl.c:			If CTL_DISABLE is turned on, don't initialize.

i386/conf/GENERIC,
amd64/conf/GENERIC:	Re-enable device ctl, and add the CTL_DISABLE
			option.

1 files changed, 7 insertions, 0 deletions

diff --git a/UPDATING b/UPDATING
index 50e6452f1cb6..ef79fa81fab8 100644
--- a/UPDATING
+++ b/UPDATING
@@ -26,6 +26,13 @@ NOTE TO PEOPLE WHO THINK THAT FreeBSD 10.x IS SLOW:
 	disable the most expensive debugging functionality run
 	"ln -s 'abort:false,junk:false' /etc/malloc.conf".)
 
+20130304:
+	The ctl device has been re-enabled in GENERIC for i386 and amd64,
+	but does not initialize by default (because of the new CTL_DISABLE
+	option) to save memory.  To re-enable it, remove the CTL_DISABLE
+	option from the kernel config file or set kern.cam.ctl.disable=0
+	in /boot/loader.conf.
+
 20130301:
 	The ctl device has been disabled in GENERIC for i386 and amd64.
 	This was done due to the extra memory being allocated at system