The patch titled
kernel/printk.c: handle more than one CON_BOOT
has been added to the -mm tree. Its filename is
kernel-printkc-handle-more-than-one-con_boot.patch
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------------------------------------------------------
Subject: kernel/printk.c: handle more than one CON_BOOT
From: Robin Getz <rgetz@xxxxxxxxxxxxxxxxxxxx>
Today, register_console() assumes the following usage:
- The first console to register with a flag set to CON_BOOT is the
one and only bootconsole.
- If another register_console() is called with an additional CON_BOOT,
it is silently rejected.
- As soon as a console without the CON_BOOT set calls registers
the bootconsole is automatically unregistered.
- Once there is a "real" console - register_console() will silently
reject any consoles with it's CON_BOOT flag set.
In many systems (alpha, blackfin, microblaze, mips, powerpc, sh, & x86),
there are early_printk implementations, which use the CON_BOOT which come
out serial ports, vga, usb, & memory buffers. In many embedded systems,
it would be nice to have two - in case the primary fails, you always have
access to a backup memory buffer - but this requires at least two CON_BOOT
consoles.
This changeset allows multiple boot consoles, and changes the functionality
to, be mostly the same as the above.
- Any number CON_BOOT consoles of can be registered
- A "real" console will unregister all the CON_BOOT consoles
- Once a "real" console is registered, no more CON_BOOT consoles
can be added (still silently rejected)
With the changeset, on boot you get:
root:/> dmesg | grep console
bootconsole [early_shadow0] enabled
bootconsole [early_BFuart0] enabled
Kernel command line: root=/dev/mtdblock0 rw earlyprintk=serial,uart0,57600 earlyprintk=shadow console=ttyBF0,57600
console handover:boot [early_BFuart0] boot [early_shadow0] -> real [ttyBF0]
or
root:/> dmesg | grep console
Kernel command line: root=/dev/mtdblock0 rw console=ttyBF0,57600
console [ttyBF0] enabled
Signed-off-by : Robin Getz <rgetz@xxxxxxxxxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Paul Mundt <lethal@xxxxxxxxxxxx>
Cc: Mike Frysinger <vapier@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/printk.c | 127 +++++++++++++++++++++++++++-------------------
1 file changed, 75 insertions(+), 52 deletions(-)
diff -puN kernel/printk.c~kernel-printkc-handle-more-than-one-con_boot kernel/printk.c
--- a/kernel/printk.c~kernel-printkc-handle-more-than-one-con_boot
+++ a/kernel/printk.c
@@ -37,6 +37,12 @@
#include <asm/uaccess.h>
/*
+ * for_each_console() allows you to iterate on each console
+ */
+#define for_each_console(con) \
+ for (con = console_drivers; con != NULL; con = con->next)
+
+/*
* Architectures can override it:
*/
void asmlinkage __attribute__((weak)) early_printk(const char *fmt, ...)
@@ -410,7 +416,7 @@ static void __call_console_drivers(unsig
{
struct console *con;
- for (con = console_drivers; con; con = con->next) {
+ for_each_console(con) {
if ((con->flags & CON_ENABLED) && con->write &&
(cpu_online(smp_processor_id()) ||
(con->flags & CON_ANYTIME)))
@@ -542,7 +548,7 @@ static int have_callable_console(void)
{
struct console *con;
- for (con = console_drivers; con; con = con->next)
+ for_each_console(con)
if (con->flags & CON_ANYTIME)
return 1;
@@ -1095,7 +1101,7 @@ void console_unblank(void)
console_locked = 1;
console_may_schedule = 0;
- for (c = console_drivers; c != NULL; c = c->next)
+ for_each_console(c)
if ((c->flags & CON_ENABLED) && c->unblank)
c->unblank();
release_console_sem();
@@ -1110,7 +1116,7 @@ struct tty_driver *console_device(int *i
struct tty_driver *driver = NULL;
acquire_console_sem();
- for (c = console_drivers; c != NULL; c = c->next) {
+ for_each_console(c) {
if (!c->device)
continue;
driver = c->device(c, index);
@@ -1148,24 +1154,33 @@ EXPORT_SYMBOL(console_start);
* print any messages that were printed by the kernel before the
* console driver was initialized.
*/
-void register_console(struct console *console)
+void register_console(struct console *newcon)
{
int i;
unsigned long flags;
- struct console *bootconsole = NULL;
+ struct console *bcon = NULL;
+ /*
+ * before we register a new CON_BOOT console, make sure we don't
+ * already have a valid console
+ */
if (console_drivers) {
- if (console->flags & CON_BOOT)
- return;
+ if (newcon->flags & CON_BOOT) {
+ /* find the last or real console */
+ for_each_console(bcon) {
+ if (!(bcon->flags & CON_BOOT))
+ return;
+ }
+ }
if (console_drivers->flags & CON_BOOT)
- bootconsole = console_drivers;
+ bcon = console_drivers;
}
- if (preferred_console < 0 || bootconsole || !console_drivers)
+ if (preferred_console < 0 || bcon || !console_drivers)
preferred_console = selected_console;
- if (console->early_setup)
- console->early_setup();
+ if (newcon->early_setup)
+ newcon->early_setup();
/*
* See if we want to use this console driver. If we
@@ -1173,13 +1188,13 @@ void register_console(struct console *co
* that registers here.
*/
if (preferred_console < 0) {
- if (console->index < 0)
- console->index = 0;
- if (console->setup == NULL ||
- console->setup(console, NULL) == 0) {
- console->flags |= CON_ENABLED;
- if (console->device) {
- console->flags |= CON_CONSDEV;
+ if (newcon->index < 0)
+ newcon->index = 0;
+ if (newcon->setup == NULL ||
+ newcon->setup(newcon, NULL) == 0) {
+ newcon->flags |= CON_ENABLED;
+ if (newcon->device) {
+ newcon->flags |= CON_CONSDEV;
preferred_console = 0;
}
}
@@ -1191,47 +1206,53 @@ void register_console(struct console *co
*/
for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
i++) {
- if (strcmp(console_cmdline[i].name, console->name) != 0)
+ if (strcmp(console_cmdline[i].name, newcon->name) != 0)
continue;
- if (console->index >= 0 &&
- console->index != console_cmdline[i].index)
+ if (newcon->index >= 0 &&
+ newcon->index != console_cmdline[i].index)
continue;
- if (console->index < 0)
- console->index = console_cmdline[i].index;
+ if (newcon->index < 0)
+ newcon->index = console_cmdline[i].index;
#ifdef CONFIG_A11Y_BRAILLE_CONSOLE
if (console_cmdline[i].brl_options) {
- console->flags |= CON_BRL;
- braille_register_console(console,
+ newcon->flags |= CON_BRL;
+ braille_register_console(newcon,
console_cmdline[i].index,
console_cmdline[i].options,
console_cmdline[i].brl_options);
return;
}
#endif
- if (console->setup &&
- console->setup(console, console_cmdline[i].options) != 0)
+ if (newcon->setup &&
+ newcon->setup(newcon, console_cmdline[i].options) != 0)
break;
- console->flags |= CON_ENABLED;
- console->index = console_cmdline[i].index;
+ newcon->flags |= CON_ENABLED;
+ newcon->index = console_cmdline[i].index;
if (i == selected_console) {
- console->flags |= CON_CONSDEV;
+ newcon->flags |= CON_CONSDEV;
preferred_console = selected_console;
}
break;
}
- if (!(console->flags & CON_ENABLED))
+ if (!(newcon->flags & CON_ENABLED))
return;
- if (bootconsole && (console->flags & CON_CONSDEV)) {
- printk(KERN_INFO "console handover: boot [%s%d] -> real [%s%d]\n",
- bootconsole->name, bootconsole->index,
- console->name, console->index);
- unregister_console(bootconsole);
- console->flags &= ~CON_PRINTBUFFER;
+ if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV)) {
+ /* we need to iterate through twice, to make sure we print
+ * everything out, before we unregister the console(s)
+ */
+ printk(KERN_INFO "console handover:");
+ for_each_console(bcon)
+ printk("boot [%s%d] ", bcon->name, bcon->index);
+ printk(" -> real [%s%d]\n", newcon->name, newcon->index);
+ for_each_console(bcon)
+ unregister_console(bcon);
+ newcon->flags &= ~CON_PRINTBUFFER;
} else {
- printk(KERN_INFO "console [%s%d] enabled\n",
- console->name, console->index);
+ printk(KERN_INFO "%sconsole [%s%d] enabled\n",
+ (newcon->flags & CON_BOOT) ? "boot" : "" ,
+ newcon->name, newcon->index);
}
/*
@@ -1239,16 +1260,16 @@ void register_console(struct console *co
* preferred driver at the head of the list.
*/
acquire_console_sem();
- if ((console->flags & CON_CONSDEV) || console_drivers == NULL) {
- console->next = console_drivers;
- console_drivers = console;
- if (console->next)
- console->next->flags &= ~CON_CONSDEV;
+ if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
+ newcon->next = console_drivers;
+ console_drivers = newcon;
+ if (newcon->next)
+ newcon->next->flags &= ~CON_CONSDEV;
} else {
- console->next = console_drivers->next;
- console_drivers->next = console;
+ newcon->next = console_drivers->next;
+ console_drivers->next = newcon;
}
- if (console->flags & CON_PRINTBUFFER) {
+ if (newcon->flags & CON_PRINTBUFFER) {
/*
* release_console_sem() will print out the buffered messages
* for us.
@@ -1300,11 +1321,13 @@ EXPORT_SYMBOL(unregister_console);
static int __init disable_boot_consoles(void)
{
- if (console_drivers != NULL) {
- if (console_drivers->flags & CON_BOOT) {
+ struct console *con;
+
+ for_each_console(con) {
+ if (con->flags & CON_BOOT) {
printk(KERN_INFO "turn off boot console %s%d\n",
- console_drivers->name, console_drivers->index);
- return unregister_console(console_drivers);
+ con->name, con->index);
+ return unregister_console(con);
}
}
return 0;
_
Patches currently in -mm which might be from rgetz@xxxxxxxxxxxxxxxxxxxx are
kernel-printkc-handle-more-than-one-con_boot.patch
asm-sections-add-text-data-checking-functions-for-arches-to-override.patch
kallsyms-use-new-arch_is_kernel_text.patch
lockdep-use-new-arch_is_kernel_data.patch
blackfin-override-text-data-checking-functions.patch
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