From: Matthew Wilcox <matthew@wil.cx>
CON_BOOT is like early printk in that it allows for output really early on.
It's better than early printk because it unregisters automatically when a
real console is initialised. So if you don't get consoles registering in
console_init, there isn't a huge delay between the boot console
unregistering and the real console starting. This is the case on PA-RISC
where we have serial ports that aren't discovered until the PCI bus has
been walked.
I think all the current early printk users could be converted to this
scheme with a minimal amount of effort.
Signed-off-by: Andrew Morton <akpm@osdl.org>
---
25-akpm/include/linux/console.h | 1 +
25-akpm/kernel/printk.c | 5 +++++
2 files changed, 6 insertions(+)
diff -puN include/linux/console.h~new-console-flag-con_boot include/linux/console.h
--- 25/include/linux/console.h~new-console-flag-con_boot 2005-03-15 22:47:16.000000000 -0800
+++ 25-akpm/include/linux/console.h 2005-03-15 22:47:16.000000000 -0800
@@ -84,6 +84,7 @@ void give_up_console(const struct consw
#define CON_PRINTBUFFER (1)
#define CON_CONSDEV (2) /* Last on the command line */
#define CON_ENABLED (4)
+#define CON_BOOT (8)
struct console
{
diff -puN kernel/printk.c~new-console-flag-con_boot kernel/printk.c
--- 25/kernel/printk.c~new-console-flag-con_boot 2005-03-15 22:47:16.000000000 -0800
+++ 25-akpm/kernel/printk.c 2005-03-15 22:47:16.000000000 -0800
@@ -861,6 +861,11 @@ void register_console(struct console * c
if (!(console->flags & CON_ENABLED))
return;
+ if (console_drivers && (console_drivers->flags & CON_BOOT)) {
+ unregister_console(console_drivers);
+ console->flags &= ~CON_PRINTBUFFER;
+ }
+
/*
* Put this console in the list - keep the
* preferred driver at the head of the list.
_