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-rw-r--r--drivers/tty/Kconfig14
-rw-r--r--drivers/tty/Makefile3
-rw-r--r--drivers/tty/ttynull.c18
-rw-r--r--include/linux/console.h3
-rw-r--r--init/main.c10
-rw-r--r--kernel/printk/printk.c9
6 files changed, 38 insertions, 19 deletions
diff --git a/drivers/tty/Kconfig b/drivers/tty/Kconfig
index 93fd984eb2f5..ca359bbd62f5 100644
--- a/drivers/tty/Kconfig
+++ b/drivers/tty/Kconfig
@@ -428,20 +428,6 @@ config MIPS_EJTAG_FDC_KGDB_CHAN
help
FDC channel number to use for KGDB.
-config NULL_TTY
- tristate "NULL TTY driver"
- help
- Say Y here if you want a NULL TTY which simply discards messages.
-
- This is useful to allow userspace applications which expect a console
- device to work without modifications even when no console is
- available or desired.
-
- In order to use this driver, you should redirect the console to this
- TTY, or boot the kernel with console=ttynull.
-
- If unsure, say N.
-
config TRACE_ROUTER
tristate "Trace data router for MIPI P1149.7 cJTAG standard"
depends on TRACE_SINK
diff --git a/drivers/tty/Makefile b/drivers/tty/Makefile
index 020b1cd9294f..f6b6bee0422d 100644
--- a/drivers/tty/Makefile
+++ b/drivers/tty/Makefile
@@ -2,7 +2,7 @@
obj-$(CONFIG_TTY) += tty_io.o n_tty.o tty_ioctl.o tty_ldisc.o \
tty_buffer.o tty_port.o tty_mutex.o \
tty_ldsem.o tty_baudrate.o tty_jobctrl.o \
- n_null.o
+ n_null.o ttynull.o
obj-$(CONFIG_LEGACY_PTYS) += pty.o
obj-$(CONFIG_UNIX98_PTYS) += pty.o
obj-$(CONFIG_AUDIT) += tty_audit.o
@@ -25,7 +25,6 @@ obj-$(CONFIG_ISI) += isicom.o
obj-$(CONFIG_MOXA_INTELLIO) += moxa.o
obj-$(CONFIG_MOXA_SMARTIO) += mxser.o
obj-$(CONFIG_NOZOMI) += nozomi.o
-obj-$(CONFIG_NULL_TTY) += ttynull.o
obj-$(CONFIG_ROCKETPORT) += rocket.o
obj-$(CONFIG_SYNCLINK_GT) += synclink_gt.o
obj-$(CONFIG_SYNCLINKMP) += synclinkmp.o
diff --git a/drivers/tty/ttynull.c b/drivers/tty/ttynull.c
index 17f05b7eb6d3..eced70ec54e1 100644
--- a/drivers/tty/ttynull.c
+++ b/drivers/tty/ttynull.c
@@ -2,6 +2,13 @@
/*
* Copyright (C) 2019 Axis Communications AB
*
+ * The console is useful for userspace applications which expect a console
+ * device to work without modifications even when no console is available
+ * or desired.
+ *
+ * In order to use this driver, you should redirect the console to this
+ * TTY, or boot the kernel with console=ttynull.
+ *
* Based on ttyprintk.c:
* Copyright (C) 2010 Samo Pogacnik
*/
@@ -59,6 +66,17 @@ static struct console ttynull_console = {
.device = ttynull_device,
};
+void __init register_ttynull_console(void)
+{
+ if (!ttynull_driver)
+ return;
+
+ if (add_preferred_console(ttynull_console.name, 0, NULL))
+ return;
+
+ register_console(&ttynull_console);
+}
+
static int __init ttynull_init(void)
{
struct tty_driver *driver;
diff --git a/include/linux/console.h b/include/linux/console.h
index 4b1e26c4cb42..9c662e41cde5 100644
--- a/include/linux/console.h
+++ b/include/linux/console.h
@@ -187,9 +187,12 @@ extern int braille_register_console(struct console *, int index,
extern int braille_unregister_console(struct console *);
#ifdef CONFIG_TTY
extern void console_sysfs_notify(void);
+extern void register_ttynull_console(void);
#else
static inline void console_sysfs_notify(void)
{ }
+static inline void register_ttynull_console(void)
+{ }
#endif
extern bool console_suspend_enabled;
diff --git a/init/main.c b/init/main.c
index 20baced721ad..08cd3a52a7e8 100644
--- a/init/main.c
+++ b/init/main.c
@@ -1480,8 +1480,14 @@ void __init console_on_rootfs(void)
struct file *file = filp_open("/dev/console", O_RDWR, 0);
if (IS_ERR(file)) {
- pr_err("Warning: unable to open an initial console.\n");
- return;
+ pr_err("Warning: unable to open an initial console. Fallback to ttynull.\n");
+ register_ttynull_console();
+
+ file = filp_open("/dev/console", O_RDWR, 0);
+ if (IS_ERR(file)) {
+ pr_err("Warning: Failed to add ttynull console. No stdin, stdout, and stderr for the init process!\n");
+ return;
+ }
}
init_dup(file);
init_dup(file);
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index c8847ee571f0..ccbdac579bd0 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -2236,8 +2236,15 @@ static int __init console_setup(char *str)
char *s, *options, *brl_options = NULL;
int idx;
- if (str[0] == 0)
+ /*
+ * console="" or console=null have been suggested as a way to
+ * disable console output. Use ttynull that has been created
+ * for exacly this purpose.
+ */
+ if (str[0] == 0 || strcmp(str, "null") == 0) {
+ __add_preferred_console("ttynull", 0, NULL, NULL, true);
return 1;
+ }
if (_braille_console_setup(&str, &brl_options))
return 1;