tty: Added a CONFIG_TTY option to allow removal of TTY

The option allows you to remove TTY and compile without errors. This
saves space on systems that won't support TTY interfaces anyway.
bloat-o-meter output is below.

The bulk of this patch consists of Kconfig changes adding "depends on
TTY" to various serial devices and similar drivers that require the TTY
layer.  Ideally, these dependencies would occur on a common intermediate
symbol such as SERIO, but most drivers "select SERIO" rather than
"depends on SERIO", and "select" does not respect dependencies.

bloat-o-meter output comparing our previous minimal to new minimal by
removing TTY.  The list is filtered to not show removed entries with awk
'$3 != "-"' as the list was very long.

add/remove: 0/226 grow/shrink: 2/14 up/down: 6/-35356 (-35350)
function                                     old     new   delta
chr_dev_init                                 166     170      +4
allow_signal                                  80      82      +2
static.__warned                              143     142      -1
disallow_signal                               63      62      -1
__set_special_pids                            95      94      -1
unregister_console                           126     121      -5
start_kernel                                 546     541      -5
register_console                             593     588      -5
copy_from_user                                45      40      -5
sys_setsid                                   128     120      -8
sys_vhangup                                   32      19     -13
do_exit                                     1543    1526     -17
bitmap_zero                                   60      40     -20
arch_local_irq_save                          137     117     -20
release_task                                 674     652     -22
static.spin_unlock_irqrestore                308     260     -48

Signed-off-by: Joe Millenbach <jmillenbach@gmail.com>
Reviewed-by: Jamey Sharp <jamey@minilop.net>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

7 files changed, 8 insertions, 1 deletions

diff --git a/arch/alpha/Kconfig b/arch/alpha/Kconfig
index 9d5904cc7712..1ef196ddadeb 100644
--- a/arch/alpha/Kconfig
+++ b/arch/alpha/Kconfig
@@ -125,6 +125,7 @@ choice
 
 config ALPHA_GENERIC
         bool "Generic"
+        depends on TTY
         help
           A generic kernel will run on all supported Alpha hardware.
 
@@ -491,6 +492,7 @@ config VGA_HOSE
 
 config ALPHA_SRM
         bool "Use SRM as bootloader" if ALPHA_CABRIOLET || ALPHA_AVANTI_CH || ALPHA_EB64P || ALPHA_PC164 || ALPHA_TAKARA || ALPHA_EB164 || ALPHA_ALCOR || ALPHA_MIATA || ALPHA_LX164 || ALPHA_SX164 || ALPHA_NAUTILUS || ALPHA_NONAME
+        depends on TTY
         default y if ALPHA_JENSEN || ALPHA_MIKASA || ALPHA_SABLE || ALPHA_LYNX || ALPHA_NORITAKE || ALPHA_DP264 || ALPHA_RAWHIDE || ALPHA_EIGER || ALPHA_WILDFIRE || ALPHA_TITAN || ALPHA_SHARK || ALPHA_MARVEL
         ---help---
           There are two different types of booting firmware on Alphas: SRM,
diff --git a/arch/ia64/hp/sim/Kconfig b/arch/ia64/hp/sim/Kconfig
index 8d513a8c5266..d84707d55203 100644
--- a/arch/ia64/hp/sim/Kconfig
+++ b/arch/ia64/hp/sim/Kconfig
@@ -8,6 +8,7 @@ config HP_SIMETH
 
 config HP_SIMSERIAL
         bool "Simulated serial driver support"
+        depends on TTY
 
 config HP_SIMSERIAL_CONSOLE
         bool "Console for HP simulator"
diff --git a/arch/m68k/Kconfig.devices b/arch/m68k/Kconfig.devices
index c4cdfe444c64..4bc945dfe467 100644
--- a/arch/m68k/Kconfig.devices
+++ b/arch/m68k/Kconfig.devices
@@ -41,7 +41,7 @@ config NFBLOCK
 
 config NFCON
         tristate "NatFeat console driver"
-        depends on NATFEAT
+        depends on TTY && NATFEAT
         help
           Say Y to include support for the ARAnyM NatFeat console driver
           which allows the console output to be redirected to the stderr
diff --git a/arch/parisc/Kconfig b/arch/parisc/Kconfig
index b77feffbadea..df5beb639760 100644
--- a/arch/parisc/Kconfig
+++ b/arch/parisc/Kconfig
@@ -23,6 +23,7 @@ config PARISC
         select HAVE_MOD_ARCH_SPECIFIC
         select MODULES_USE_ELF_RELA
         select CLONE_BACKWARDS
+        select TTY # Needed for pdc_cons.c
 
         help
           The PA-RISC microprocessor is designed by Hewlett-Packard and used
diff --git a/arch/tile/Kconfig b/arch/tile/Kconfig
index 875d008828b8..ae8a7ca67fa4 100644
--- a/arch/tile/Kconfig
+++ b/arch/tile/Kconfig
@@ -121,6 +121,7 @@ config DEBUG_COPY_FROM_USER
         def_bool n
 
 config HVC_TILE
+        depends on TTY
         select HVC_DRIVER
         def_bool y
 
diff --git a/arch/um/Kconfig.common b/arch/um/Kconfig.common
index 648121b037d5..bceee6623b00 100644
--- a/arch/um/Kconfig.common
+++ b/arch/um/Kconfig.common
@@ -12,6 +12,7 @@ config UML
         select GENERIC_CPU_DEVICES
         select GENERIC_IO
         select GENERIC_CLOCKEVENTS
+        select TTY # Needed for line.c
 
 config MMU
         bool
diff --git a/arch/xtensa/Kconfig b/arch/xtensa/Kconfig
index 5aab1acabf1c..ad64c73b8675 100644
--- a/arch/xtensa/Kconfig
+++ b/arch/xtensa/Kconfig
@@ -132,6 +132,7 @@ choice
 
 config XTENSA_PLATFORM_ISS
         bool "ISS"
+        depends on TTY
         select XTENSA_CALIBRATE_CCOUNT
         select SERIAL_CONSOLE
         select XTENSA_ISS_NETWORK