diff options
| -rw-r--r-- | drivers/tty/Kconfig | 14 | ||||
| -rw-r--r-- | drivers/tty/Makefile | 3 | ||||
| -rw-r--r-- | drivers/tty/ttynull.c | 18 | ||||
| -rw-r--r-- | include/linux/console.h | 3 | ||||
| -rw-r--r-- | init/main.c | 10 | ||||
| -rw-r--r-- | kernel/printk/printk.c | 9 |
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; |