MIPS: Fix and enhance built-in kernel command line

Currently, MIPS kernels silently overwrite kernel command-line parameters
hardcoded in CONFIG_CMDLINE by the ones received from firmware.  Therefore,
using firmware remains the only reliable method to transfer the
command-line parameters, which is not always desirable or convenient, and
the CONFIG_CMDLINE option is thereby effectively rendered useless.

This patch fixes the problem described above and introduces a more flexible
scheme of handling the kernel command line, in a manner identical to what is
currently used for x86.  The default behavior, i.e. when CONFIG_CMDLINE_BOOL
is not defined, retains the existing semantics, and firmware command-line
arguments override the hardcoded ones.

[Ralf: I fixed up all the defconfig files so the stay unaffected by this
change.]

Signed-off-by: Dmitri Vorobiev <dmitri.vorobiev@movial.com>
Cc: linux-mips@linux-mips.org
Patchwork: http://patchwork.linux-mips.org/patch/689/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/Kconfig.debug

@@ -20,15 +20,52 @@ config EARLY_PRINTK
 	  doesn't cooperate with an X server. You should normally say N here,
 	  unless you want to debug such a crash.
 
+config CMDLINE_BOOL
+	bool "Built-in kernel command line"
+	default n
+	help
+	  For most systems, it is firmware or second stage bootloader that
+	  by default specifies the kernel command line options.  However,
+	  it might be necessary or advantageous to either override the
+	  default kernel command line or add a few extra options to it.
+	  For such cases, this option allows you to hardcode your own
+	  command line options directly into the kernel.  For that, you
+	  should choose 'Y' here, and fill in the extra boot arguments
+	  in CONFIG_CMDLINE.
+
+	  The built-in options will be concatenated to the default command
+	  line if CMDLINE_OVERRIDE is set to 'N'. Otherwise, the default
+	  command line will be ignored and replaced by the built-in string.
+
+	  Most MIPS systems will normally expect 'N' here and rely upon
+	  the command line from the firmware or the second-stage bootloader.
+
 config CMDLINE
 	string "Default kernel command string"
+	depends on CMDLINE_BOOL
 	default ""
 	help
 	  On some platforms, there is currently no way for the boot loader to
-	  pass arguments to the kernel. For these platforms, you can supply
-	  some command-line options at build time by entering them here.  In
-	  other cases you can specify kernel args so that you don't have
-	  to set them up in board prom initialization routines.
+	  pass arguments to the kernel.  For these platforms, and for the cases
+	  when you want to add some extra options to the command line or ignore
+	  the default command line, you can supply some command-line options at
+	  build time by entering them here.  In other cases you can specify
+	  kernel args so that you don't have to set them up in board prom
+	  initialization routines.
+
+	  For more information, see the CMDLINE_BOOL and CMDLINE_OVERRIDE
+	  options.
+
+config CMDLINE_OVERRIDE
+	bool "Built-in command line overrides firware arguments"
+	default n
+	depends on CMDLINE_BOOL
+	help
+	  By setting this option to 'Y' you will have your kernel ignore
+	  command line arguments from firmware or second stage bootloader.
+	  Instead, the built-in command line will be used exclusively.
+
+	  Normally, you will choose 'N' here.
 
 config DEBUG_STACK_USAGE
 	bool "Enable stack utilization instrumentation"

arch/mips/configs/ar7_defconfig

@@ -1051,7 +1051,9 @@ CONFIG_TRACING_SUPPORT=y
 # CONFIG_DYNAMIC_DEBUG is not set
 # CONFIG_SAMPLES is not set
 CONFIG_HAVE_ARCH_KGDB=y
+CONFIG_CMDLINE_BOOL=y
 CONFIG_CMDLINE="rootfstype=squashfs,jffs2"
+# CONFIG_CMDLINE_OVERRIDE is not set
 
 #
 # Security options

arch/mips/configs/bcm47xx_defconfig

@@ -1852,7 +1852,7 @@ CONFIG_DEBUG_FS=y
 # CONFIG_HEADERS_CHECK is not set
 # CONFIG_DEBUG_KERNEL is not set
 # CONFIG_SAMPLES is not set
-CONFIG_CMDLINE=""
+# CONFIG_CMDLINE_BOOL is not set
 
 #
 # Security options

arch/mips/configs/bcm63xx_defconfig

@@ -941,7 +941,9 @@ CONFIG_TRACING_SUPPORT=y
 # CONFIG_BLK_DEV_IO_TRACE is not set
 # CONFIG_SAMPLES is not set
 CONFIG_HAVE_ARCH_KGDB=y
+CONFIG_CMDLINE_BOOL=y
 CONFIG_CMDLINE="console=ttyS0,115200"
+# CONFIG_CMDLINE_OVERRIDE is not set
 
 #
 # Security options

arch/mips/configs/bigsur_defconfig

@@ -1236,7 +1236,7 @@ CONFIG_DEBUG_MUTEXES=y
 # CONFIG_BACKTRACE_SELF_TEST is not set
 # CONFIG_FAULT_INJECTION is not set
 # CONFIG_SAMPLES is not set
-CONFIG_CMDLINE=""
+# CONFIG_CMDLINE_BOOL is not set
 # CONFIG_DEBUG_STACK_USAGE is not set
 # CONFIG_SB1XXX_CORELIS is not set
 # CONFIG_RUNTIME_DEBUG is not set

arch/mips/configs/capcella_defconfig

@@ -782,7 +782,9 @@ CONFIG_ENABLE_MUST_CHECK=y
 # CONFIG_HEADERS_CHECK is not set
 # CONFIG_DEBUG_KERNEL is not set
 CONFIG_CROSSCOMPILE=y
+CONFIG_CMDLINE_BOOL=y
 CONFIG_CMDLINE="mem=32M console=ttyVR0,38400"
+# CONFIG_CMDLINE_OVERRIDE is not set
 
 #
 # Security options

arch/mips/configs/cavium-octeon_defconfig

@@ -820,7 +820,7 @@ CONFIG_SYSCTL_SYSCALL_CHECK=y
 # CONFIG_SAMPLES is not set
 CONFIG_HAVE_ARCH_KGDB=y
 # CONFIG_KGDB is not set
-CONFIG_CMDLINE=""
+# CONFIG_CMDLINE_BOOL is not set
 # CONFIG_DEBUG_STACK_USAGE is not set
 # CONFIG_RUNTIME_DEBUG is not set
 

arch/mips/configs/cobalt_defconfig

@@ -1125,7 +1125,7 @@ CONFIG_FRAME_WARN=1024
 # CONFIG_SLUB_STATS is not set
 # CONFIG_DEBUG_MEMORY_INIT is not set
 # CONFIG_SAMPLES is not set
-CONFIG_CMDLINE=""
+# CONFIG_CMDLINE_BOOL is not set
 
 #
 # Security options

arch/mips/configs/db1000_defconfig

@@ -1089,7 +1089,7 @@ CONFIG_ENABLE_MUST_CHECK=y
 # CONFIG_DEBUG_KERNEL is not set
 CONFIG_LOG_BUF_SHIFT=14
 CONFIG_CROSSCOMPILE=y
-CONFIG_CMDLINE=""
+# CONFIG_CMDLINE_BOOL is not set
 
 #
 # Security options

arch/mips/configs/db1100_defconfig

@@ -1089,7 +1089,7 @@ CONFIG_ENABLE_MUST_CHECK=y
 # CONFIG_DEBUG_KERNEL is not set
 CONFIG_LOG_BUF_SHIFT=14
 CONFIG_CROSSCOMPILE=y
-CONFIG_CMDLINE=""
+# CONFIG_CMDLINE_BOOL is not set
 
 #
 # Security options

arch/mips/configs/db1200_defconfig

@@ -1171,7 +1171,9 @@ CONFIG_ENABLE_MUST_CHECK=y
 # CONFIG_DEBUG_KERNEL is not set
 CONFIG_LOG_BUF_SHIFT=14
 CONFIG_CROSSCOMPILE=y
+CONFIG_CMDLINE_BOOL=y
 CONFIG_CMDLINE="mem=48M"
+# CONFIG_CMDLINE_OVERRIDE is not set
 
 #
 # Security options

arch/mips/configs/db1500_defconfig

@@ -1389,7 +1389,7 @@ CONFIG_ENABLE_MUST_CHECK=y
 # CONFIG_DEBUG_KERNEL is not set
 CONFIG_LOG_BUF_SHIFT=14
 CONFIG_CROSSCOMPILE=y
-CONFIG_CMDLINE=""
+# CONFIG_CMDLINE_BOOL is not set
 
 #
 # Security options

arch/mips/configs/db1550_defconfig

@@ -1206,7 +1206,7 @@ CONFIG_ENABLE_MUST_CHECK=y
 # CONFIG_DEBUG_KERNEL is not set
 CONFIG_LOG_BUF_SHIFT=14
 CONFIG_CROSSCOMPILE=y
-CONFIG_CMDLINE=""
+# CONFIG_CMDLINE_BOOL is not set
 
 #
 # Security options

arch/mips/configs/decstation_defconfig

@@ -881,7 +881,7 @@ CONFIG_MAGIC_SYSRQ=y
 # CONFIG_DEBUG_KERNEL is not set
 CONFIG_LOG_BUF_SHIFT=14
 CONFIG_CROSSCOMPILE=y
-CONFIG_CMDLINE=""
+# CONFIG_CMDLINE_BOOL is not set
 
 #
 # Security options

arch/mips/configs/e55_defconfig

@@ -560,7 +560,9 @@ CONFIG_ENABLE_MUST_CHECK=y
 # CONFIG_HEADERS_CHECK is not set
 # CONFIG_DEBUG_KERNEL is not set
 CONFIG_CROSSCOMPILE=y
+CONFIG_CMDLINE_BOOL=y
 CONFIG_CMDLINE="console=ttyVR0,19200 ide0=0x1f0,0x3f6,40 mem=8M"
+# CONFIG_CMDLINE_OVERRIDE is not set
 
 #
 # Security options

arch/mips/configs/fuloong2e_defconfig

@@ -1710,7 +1710,7 @@ CONFIG_TRACING_SUPPORT=y
 # CONFIG_DYNAMIC_DEBUG is not set
 # CONFIG_SAMPLES is not set
 CONFIG_HAVE_ARCH_KGDB=y
-CONFIG_CMDLINE=""
+# CONFIG_CMDLINE_BOOL is not set
 
 #
 # Security options

arch/mips/configs/ip22_defconfig

@@ -1187,7 +1187,7 @@ CONFIG_DEBUG_MEMORY_INIT=y
 CONFIG_DYNAMIC_PRINTK_DEBUG=y
 # CONFIG_SAMPLES is not set
 CONFIG_HAVE_ARCH_KGDB=y
-CONFIG_CMDLINE=""
+# CONFIG_CMDLINE_BOOL is not set
 
 #
 # Security options

arch/mips/configs/ip27_defconfig

@@ -939,7 +939,7 @@ CONFIG_ENABLE_MUST_CHECK=y
 # CONFIG_HEADERS_CHECK is not set
 # CONFIG_DEBUG_KERNEL is not set
 CONFIG_CROSSCOMPILE=y
-CONFIG_CMDLINE=""
+# CONFIG_CMDLINE_BOOL is not set
 
 #
 # Security options

arch/mips/configs/ip28_defconfig

@@ -815,7 +815,7 @@ CONFIG_MAGIC_SYSRQ=y
 # CONFIG_HEADERS_CHECK is not set
 # CONFIG_DEBUG_KERNEL is not set
 # CONFIG_SAMPLES is not set
-CONFIG_CMDLINE=""
+# CONFIG_CMDLINE_BOOL is not set
 
 #
 # Security options

arch/mips/configs/ip32_defconfig

@@ -1125,7 +1125,7 @@ CONFIG_SYSCTL_SYSCALL_CHECK=y
 # CONFIG_DYNAMIC_PRINTK_DEBUG is not set
 # CONFIG_SAMPLES is not set
 CONFIG_HAVE_ARCH_KGDB=y
-CONFIG_CMDLINE=""
+# CONFIG_CMDLINE_BOOL is not set
 
 #
 # Security options

arch/mips/configs/jazz_defconfig

@@ -1373,7 +1373,7 @@ CONFIG_ENABLE_MUST_CHECK=y
 # CONFIG_DEBUG_KERNEL is not set
 CONFIG_LOG_BUF_SHIFT=14
 CONFIG_CROSSCOMPILE=y
-CONFIG_CMDLINE=""
+# CONFIG_CMDLINE_BOOL is not set
 
 #
 # Security options

arch/mips/configs/jmr3927_defconfig

@@ -834,7 +834,7 @@ CONFIG_SYSCTL_SYSCALL_CHECK=y
 # CONFIG_DYNAMIC_PRINTK_DEBUG is not set
 # CONFIG_SAMPLES is not set
 CONFIG_HAVE_ARCH_KGDB=y
-CONFIG_CMDLINE=""
+# CONFIG_CMDLINE_BOOL is not set
 
 #
 # Security options

arch/mips/configs/lasat_defconfig

@@ -797,7 +797,7 @@ CONFIG_MAGIC_SYSRQ=y
 # CONFIG_HEADERS_CHECK is not set
 # CONFIG_DEBUG_KERNEL is not set
 CONFIG_CROSSCOMPILE=y
-CONFIG_CMDLINE=""
+# CONFIG_CMDLINE_BOOL is not set
 
 #
 # Security options

arch/mips/configs/lemote2f_defconfig

@@ -1707,7 +1707,7 @@ CONFIG_TRACING_SUPPORT=y
 # CONFIG_FTRACE is not set
 # CONFIG_SAMPLES is not set
 CONFIG_HAVE_ARCH_KGDB=y
-CONFIG_CMDLINE=""
+# CONFIG_CMDLINE_BOOL is not set
 
 #
 # Security options

arch/mips/configs/malta_defconfig

@@ -1590,7 +1590,7 @@ CONFIG_FRAME_WARN=1024
 # CONFIG_DYNAMIC_PRINTK_DEBUG is not set
 # CONFIG_SAMPLES is not set
 CONFIG_HAVE_ARCH_KGDB=y
-CONFIG_CMDLINE=""
+# CONFIG_CMDLINE_BOOL is not set
 
 #
 # Security options

arch/mips/configs/markeins_defconfig

@@ -1365,7 +1365,9 @@ CONFIG_ENABLE_MUST_CHECK=y
 # CONFIG_DEBUG_KERNEL is not set
 CONFIG_LOG_BUF_SHIFT=14
 CONFIG_CROSSCOMPILE=y
+CONFIG_CMDLINE_BOOL=y
 CONFIG_CMDLINE="console=ttyS0,115200 mem=192m ip=bootp root=/dev/nfs rw"
+# CONFIG_CMDLINE_OVERRIDE is not set
 
 #
 # Security options

arch/mips/configs/mipssim_defconfig

@@ -634,7 +634,9 @@ CONFIG_FORCED_INLINING=y
 # CONFIG_RCU_TORTURE_TEST is not set
 # CONFIG_FAULT_INJECTION is not set
 CONFIG_CROSSCOMPILE=y
+CONFIG_CMDLINE_BOOL=y
 CONFIG_CMDLINE="nfsroot=192.168.192.169:/u1/mipsel,timeo=20 ip=dhcp"
+# CONFIG_CMDLINE_OVERRIDE is not set
 # CONFIG_DEBUG_STACK_USAGE is not set
 # CONFIG_RUNTIME_DEBUG is not set
 

arch/mips/configs/mpc30x_defconfig

@@ -816,7 +816,9 @@ CONFIG_ENABLE_MUST_CHECK=y
 # CONFIG_HEADERS_CHECK is not set
 # CONFIG_DEBUG_KERNEL is not set
 CONFIG_CROSSCOMPILE=y
+CONFIG_CMDLINE_BOOL=y
 CONFIG_CMDLINE="mem=32M console=ttyVR0,19200 ide0=0x170,0x376,73"
+# CONFIG_CMDLINE_OVERRIDE is not set
 
 #
 # Security options

arch/mips/configs/msp71xx_defconfig

@@ -1411,7 +1411,7 @@ CONFIG_FORCED_INLINING=y
 # CONFIG_RCU_TORTURE_TEST is not set
 # CONFIG_FAULT_INJECTION is not set
 CONFIG_CROSSCOMPILE=y
-CONFIG_CMDLINE=""
+# CONFIG_CMDLINE_BOOL is not set
 # CONFIG_DEBUG_STACK_USAGE is not set
 # CONFIG_RUNTIME_DEBUG is not set
 # CONFIG_MIPS_UNCACHED is not set

arch/mips/configs/mtx1_defconfig

@@ -3017,7 +3017,7 @@ CONFIG_MAGIC_SYSRQ=y
 # CONFIG_HEADERS_CHECK is not set
 # CONFIG_DEBUG_KERNEL is not set
 CONFIG_CROSSCOMPILE=y
-CONFIG_CMDLINE=""
+# CONFIG_CMDLINE_BOOL is not set
 
 #
 # Security options

arch/mips/configs/pb1100_defconfig

@@ -1082,7 +1082,7 @@ CONFIG_ENABLE_MUST_CHECK=y
 # CONFIG_DEBUG_KERNEL is not set
 CONFIG_LOG_BUF_SHIFT=14
 CONFIG_CROSSCOMPILE=y
-CONFIG_CMDLINE=""
+# CONFIG_CMDLINE_BOOL is not set
 
 #
 # Security options

arch/mips/configs/pb1500_defconfig

@@ -1199,7 +1199,7 @@ CONFIG_ENABLE_MUST_CHECK=y
 # CONFIG_DEBUG_KERNEL is not set
 CONFIG_LOG_BUF_SHIFT=14
 CONFIG_CROSSCOMPILE=y
-CONFIG_CMDLINE=""
+# CONFIG_CMDLINE_BOOL is not set
 
 #
 # Security options

arch/mips/configs/pb1550_defconfig

@@ -1192,7 +1192,7 @@ CONFIG_ENABLE_MUST_CHECK=y
 # CONFIG_DEBUG_KERNEL is not set
 CONFIG_LOG_BUF_SHIFT=14
 CONFIG_CROSSCOMPILE=y
-CONFIG_CMDLINE=""
+# CONFIG_CMDLINE_BOOL is not set
 
 #
 # Security options

arch/mips/configs/pnx8335-stb225_defconfig

@@ -1033,7 +1033,7 @@ CONFIG_FRAME_WARN=1024
 # CONFIG_DEBUG_KERNEL is not set
 # CONFIG_SAMPLES is not set
 # CONFIG_KERNEL_TESTS is not set
-CONFIG_CMDLINE=""
+# CONFIG_CMDLINE_BOOL is not set
 
 #
 # Security options

arch/mips/configs/pnx8550-jbs_defconfig

@@ -1214,7 +1214,9 @@ CONFIG_DEBUG_MUTEXES=y
 CONFIG_FORCED_INLINING=y
 # CONFIG_RCU_TORTURE_TEST is not set
 CONFIG_CROSSCOMPILE=y
+CONFIG_CMDLINE_BOOL=y
 CONFIG_CMDLINE="console=ttyS1,38400n8 root=/dev/nfs ip=bootp"
+# CONFIG_CMDLINE_OVERRIDE is not set
 # CONFIG_DEBUG_STACK_USAGE is not set
 # CONFIG_RUNTIME_DEBUG is not set
 

arch/mips/configs/pnx8550-stb810_defconfig

@@ -1204,7 +1204,9 @@ CONFIG_DEBUG_SLAB=y
 CONFIG_FORCED_INLINING=y
 # CONFIG_RCU_TORTURE_TEST is not set
 CONFIG_CROSSCOMPILE=y
+CONFIG_CMDLINE_BOOL=y
 CONFIG_CMDLINE="console=ttyS1,38400n8 root=/dev/nfs ip=bootp"
+# CONFIG_CMDLINE_OVERRIDE is not set
 # CONFIG_DEBUG_STACK_USAGE is not set
 # CONFIG_RUNTIME_DEBUG is not set
 

arch/mips/configs/powertv_defconfig

@@ -1418,7 +1418,9 @@ CONFIG_BRANCH_PROFILE_NONE=y
 CONFIG_HAVE_ARCH_KGDB=y
 # CONFIG_KGDB is not set
 # CONFIG_KMEMCHECK is not set
+CONFIG_CMDLINE_BOOL=y
 CONFIG_CMDLINE="rw dhash_entries=1024 ihash_entries=1024 ip=10.0.1.3:10.0.1.1:10.0.1.1:255.255.255.0:zeus:eth0: root=/dev/nfs nfsroot=/nfsroot/cramfs,wsize=512,rsize=512,tcp nokgdb console=ttyUSB0,115200 memsize=252M"
+# CONFIG_CMDLINE_OVERRIDE is not set
 # CONFIG_DEBUG_STACK_USAGE is not set
 # CONFIG_RUNTIME_DEBUG is not set
 

arch/mips/configs/rb532_defconfig

@@ -1203,7 +1203,7 @@ CONFIG_FRAME_WARN=1024
 # CONFIG_HEADERS_CHECK is not set
 # CONFIG_DEBUG_KERNEL is not set
 # CONFIG_SAMPLES is not set
-CONFIG_CMDLINE=""
+# CONFIG_CMDLINE_BOOL is not set
 
 #
 # Security options

arch/mips/configs/rbtx49xx_defconfig

@@ -1061,7 +1061,7 @@ CONFIG_TRACING_SUPPORT=y
 # CONFIG_DYNAMIC_DEBUG is not set
 # CONFIG_SAMPLES is not set
 CONFIG_HAVE_ARCH_KGDB=y
-CONFIG_CMDLINE=""
+# CONFIG_CMDLINE_BOOL is not set
 
 #
 # Security options

arch/mips/configs/rm200_defconfig

@@ -1693,7 +1693,7 @@ CONFIG_ENABLE_MUST_CHECK=y
 # CONFIG_DEBUG_KERNEL is not set
 CONFIG_LOG_BUF_SHIFT=14
 CONFIG_CROSSCOMPILE=y
-CONFIG_CMDLINE=""
+# CONFIG_CMDLINE_BOOL is not set
 
 #
 # Security options

arch/mips/configs/sb1250-swarm_defconfig

@@ -960,7 +960,7 @@ CONFIG_ENABLE_MUST_CHECK=y
 # CONFIG_HEADERS_CHECK is not set
 # CONFIG_DEBUG_KERNEL is not set
 # CONFIG_SAMPLES is not set
-CONFIG_CMDLINE=""
+# CONFIG_CMDLINE_BOOL is not set
 # CONFIG_SB1XXX_CORELIS is not set
 
 #

arch/mips/configs/tb0219_defconfig

@@ -891,7 +891,9 @@ CONFIG_FRAME_WARN=1024
 # CONFIG_HEADERS_CHECK is not set
 # CONFIG_DEBUG_KERNEL is not set
 # CONFIG_SAMPLES is not set
+CONFIG_CMDLINE_BOOL=y
 CONFIG_CMDLINE="cca=3 mem=64M console=ttyVR0,115200 ip=any root=/dev/nfs"
+# CONFIG_CMDLINE_OVERRIDE is not set
 
 #
 # Security options

arch/mips/configs/tb0226_defconfig

@@ -894,7 +894,9 @@ CONFIG_FRAME_WARN=1024
 # CONFIG_HEADERS_CHECK is not set
 # CONFIG_DEBUG_KERNEL is not set
 # CONFIG_SAMPLES is not set
+CONFIG_CMDLINE_BOOL=y
 CONFIG_CMDLINE="cca=3 mem=32M console=ttyVR0,115200"
+# CONFIG_CMDLINE_OVERRIDE is not set
 
 #
 # Security options

arch/mips/configs/tb0287_defconfig

@@ -1076,7 +1076,9 @@ CONFIG_FRAME_WARN=1024
 # CONFIG_HEADERS_CHECK is not set
 # CONFIG_DEBUG_KERNEL is not set
 # CONFIG_SAMPLES is not set
+CONFIG_CMDLINE_BOOL=y
 CONFIG_CMDLINE="cca=3 mem=64M console=ttyVR0,115200 ip=any root=/dev/nfs"
+# CONFIG_CMDLINE_OVERRIDE is not set
 
 #
 # Security options

arch/mips/configs/workpad_defconfig

@@ -754,7 +754,9 @@ CONFIG_ENABLE_MUST_CHECK=y
 # CONFIG_HEADERS_CHECK is not set
 # CONFIG_DEBUG_KERNEL is not set
 CONFIG_CROSSCOMPILE=y
+CONFIG_CMDLINE_BOOL=y
 CONFIG_CMDLINE="console=ttyVR0,19200 ide0=0x170,0x376,49 mem=16M"
+# CONFIG_CMDLINE_OVERRIDE is not set
 
 #
 # Security options

arch/mips/configs/wrppmc_defconfig

@@ -886,7 +886,9 @@ CONFIG_ENABLE_MUST_CHECK=y
 # CONFIG_DEBUG_KERNEL is not set
 CONFIG_LOG_BUF_SHIFT=14
 CONFIG_CROSSCOMPILE=y
+CONFIG_CMDLINE_BOOL=y
 CONFIG_CMDLINE="console=ttyS0,115200n8"
+# CONFIG_CMDLINE_OVERRIDE is not set
 
 #
 # Security options

arch/mips/configs/yosemite_defconfig

@@ -823,7 +823,7 @@ CONFIG_DEBUG_MUTEXES=y
 CONFIG_FORCED_INLINING=y
 # CONFIG_RCU_TORTURE_TEST is not set
 CONFIG_CROSSCOMPILE=y
-CONFIG_CMDLINE=""
+# CONFIG_CMDLINE_BOOL is not set
 # CONFIG_DEBUG_STACK_USAGE is not set
 # CONFIG_RUNTIME_DEBUG is not set
 

arch/mips/kernel/setup.c

@@ -58,8 +58,12 @@ EXPORT_SYMBOL(mips_machtype);
 
 struct boot_mem_map boot_mem_map;
 
-static char command_line[COMMAND_LINE_SIZE];
-       char arcs_cmdline[COMMAND_LINE_SIZE] = CONFIG_CMDLINE;
+static char __initdata command_line[COMMAND_LINE_SIZE];
+char __initdata arcs_cmdline[COMMAND_LINE_SIZE];
+
+#ifdef CONFIG_CMDLINE_BOOL
+static char __initdata builtin_cmdline[COMMAND_LINE_SIZE] = CONFIG_CMDLINE;
+#endif
 
 /*
  * mips_io_port_base is the begin of the address space to which x86 style
@@ -458,8 +462,20 @@ static void __init arch_mem_init(char **cmdline_p)
 	pr_info("Determined physical RAM map:\n");
 	print_memory_map();
 
-	strlcpy(command_line, arcs_cmdline, sizeof(command_line));
-	strlcpy(boot_command_line, command_line, COMMAND_LINE_SIZE);
+#ifdef CONFIG_CMDLINE_BOOL
+#ifdef CONFIG_CMDLINE_OVERRIDE
+	strlcpy(boot_command_line, builtin_cmdline, COMMAND_LINE_SIZE);
+#else
+	if (builtin_cmdline[0]) {
+		strlcat(arcs_cmdline, " ", COMMAND_LINE_SIZE);
+		strlcat(arcs_cmdline, builtin_cmdline, COMMAND_LINE_SIZE);
+	}
+	strlcpy(boot_command_line, arcs_cmdline, COMMAND_LINE_SIZE);
+#endif
+#else
+	strlcpy(boot_command_line, arcs_cmdline, COMMAND_LINE_SIZE);
+#endif
+	strlcpy(command_line, boot_command_line, COMMAND_LINE_SIZE);
 
 	*cmdline_p = command_line;