Re: 3.0 wishlist Was: Overview of 2.2.x goals?

David Woodhouse (Dave@imladris.demon.co.uk)
Tue, 20 Jan 1998 19:19:55 +0000

pb@nexus.co.uk said:
> It would be a neat trick for someone to implement to have kernel
> messages optionally copied to the parallel port. Then, with the aid
> of one of the old dot-matrix printers that everybody has lying in
> their cupboards, you have an instant record of any oopses.

> p.

Here's a start - it allows "console" devices to be registered and unregistered
by modules, so the lp_console can be running only when you want it, not all
the time.

For an example of code which uses this, see Patrick Caulfield's MDA device
driver, which is on Sunsite. All you need is a non-IRQ driven character output
routine, and it's fairly trivial from then on.

--- linux/kernel/printk.c.precons Fri Dec 5 11:40:33 1997
+++ linux/kernel/printk.c Fri Dec 5 12:23:13 1997
@@ -378,6 +378,26 @@
}
}

+
+int unregister_console(struct console * console)
+{
+ struct console *a,*b;
+
+ if (console_drivers == console) {
+ console_drivers=console->next;
+ return (0);
+ }
+ for (a=console_drivers->next, b=console_drivers ;
+ a; b=a, a=b->next) {
+ if (a == console) {
+ b->next = a->next;
+ return 0;
+ }
+ }
+
+ return (1);
+}
+
/*
* Write a message to a certain tty, not just the console. This is used for
* messages that need to be redirected to a specific tty.
--- linux/kernel/ksyms.c.precons Tue Dec 2 19:41:45 1997
+++ linux/kernel/ksyms.c Fri Dec 5 11:58:42 1997
@@ -50,6 +50,7 @@
#include <linux/swap.h>
#include <linux/ctype.h>
#include <linux/file.h>
+#include <linux/console.h>

extern unsigned char aux_device_present, kbd_read_mask;

@@ -401,3 +402,7 @@
/* binfmt_aout */
EXPORT_SYMBOL(get_write_access);
EXPORT_SYMBOL(put_write_access);
+
+/* dynamic registering of consoles */
+EXPORT_SYMBOL(register_console);
+EXPORT_SYMBOL(unregister_console);
--- linux/include/linux/console.h.precons Thu Dec 4 23:27:11 1997
+++ linux/include/linux/console.h Fri Dec 5 11:58:42 1997
@@ -99,6 +99,7 @@
};

extern void register_console(struct console *);
+extern int unregister_console(struct console *);
extern struct console *console_drivers;

#endif /* linux/console.h */

-- 
----                              ----                              ----
David Woodhouse, Robinson College, CB3 9AN, England.   (+44) 0976 658355
    Dave@imladris.demon.co.uk        http://dwmw2.robinson.cam.ac.uk
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