From: Adam Simonelli <adamsimonelli@xxxxxxxxx>
The new config option, CONFIG_NULL_TTY_CONSOLE will allow ttynull to be
initialized by console_initcall() and selected as a possible console
device.
Signed-off-by: Adam Simonelli <adamsimonelli@xxxxxxxxx>
---
drivers/tty/Kconfig | 15 ++++++++++++++-
drivers/tty/ttynull.c | 20 +++++++++++++++++++-
2 files changed, 33 insertions(+), 2 deletions(-)
diff --git a/drivers/tty/Kconfig b/drivers/tty/Kconfig
index 63a494d36a1f..b4afae8b0e74 100644
--- a/drivers/tty/Kconfig
+++ b/drivers/tty/Kconfig
@@ -383,7 +383,20 @@ config NULL_TTY
available or desired.
In order to use this driver, you should redirect the console to this
- TTY, or boot the kernel with console=ttynull.
+ TTY, boot the kernel with console=ttynull, or enable
+ CONFIG_NULL_TTY_CONSOLE.
+
+ If unsure, say N.
+
+config NULL_TTY_CONSOLE
+ bool "Support for console on ttynull"
+ depends on NULL_TTY=y && !VT_CONSOLE
+ help
+ Say Y here if you want the NULL TTY to be used as a /dev/console
+ device.
+
+ This is similar to CONFIG_VT_CONSOLE, but without the dependency on
+ CONFIG_VT. It uses the ttynull driver as the system console.
If unsure, say N.
diff --git a/drivers/tty/ttynull.c b/drivers/tty/ttynull.c
index 6b2f7208b564..ec3dd3fd41c0 100644
--- a/drivers/tty/ttynull.c
+++ b/drivers/tty/ttynull.c
@@ -57,6 +57,13 @@ static struct tty_driver *ttynull_device(struct console *c, int *index)
static struct console ttynull_console = {
.name = "ttynull",
.device = ttynull_device,
+
+ /*
+ * Match the index and flags from other boot consoles when CONFIG_NULL_TTY_CONSOLE is
+ * enabled, otherwise, use the default values for the index and flags.
+ */
+ .index = IS_ENABLED(CONFIG_NULL_TTY_CONSOLE) ? -1 : 0,
+ .flags = IS_ENABLED(CONFIG_NULL_TTY_CONSOLE) ? CON_PRINTBUFFER : 0,
};
static int __init ttynull_init(void)
@@ -90,11 +97,22 @@ static int __init ttynull_init(void)
}
ttynull_driver = driver;
- register_console(&ttynull_console);
+ if (!console_is_registered(&ttynull_console))
+ register_console(&ttynull_console);
return 0;
}
+#ifdef CONFIG_NULL_TTY_CONSOLE
+static int __init ttynull_register(void)
+{
+ if (!console_is_registered(&ttynull_console))
+ register_console(&ttynull_console);
+ return 0;
+}
+console_initcall(ttynull_register);
+#endif
+
static void __exit ttynull_exit(void)
{
unregister_console(&ttynull_console);
--
2.45.2
