Messages in this thread Patch in this message | | | From | Robin Getz <> | Subject | RFC - printk handling more than one CON_BOOT | Date | Mon, 29 Jun 2009 07:03:21 -0400 |
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Today, register_console() assumes the following usage (with respect to boot consoles/early_printk).
The first console to register with register_console() with a flags set to CON_BOOT is the one and only bootconsole.
If another register_console() is called with an additional CON_BOOT, today it is silently rejected.
As soon as a console without the CON_BOOT set calls register_console(), the one and only bootconsole is automatically unregistered.
Once there is a "standard" console - register_console() will silently reject any consoles with it's CON_BOOT, set.
This changeset allows multiple boot consoles, and changes the functionality to, be mostly the same as the above.
Any number of bootconsoles can be registered. A "real" console will unregister all the bootconsoles. Once a "real" console is registered, no more bootconsoles can be added.
Thoughts?
The use case is to have a console buffer which goes to serial, and a console buffer which goes to a fixed memory buffer at the same time. (serial is what most people use, but if serial is hosed for some reason, having things in a buffer (which gets printed out by the bootloader) is the only way to tell what is going on).
If you don't object I will send a properly formatted patch...
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Index: kernel/printk.c =================================================================== --- kernel/printk.c (revision 6860) +++ kernel/printk.c (working copy) @@ -1126,9 +1126,24 @@ unsigned long flags; struct console *bootconsole = 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 (console->flags & CON_BOOT) { + for (bootconsole = console_drivers; + bootconsole != NULL; + bootconsole = bootconsole->next) { + if (!(bootconsole->flags & CON_BOOT)) + break; + } + if ((console->flags & CON_BOOT) && + !(bootconsole->flags & CON_BOOT)) + return; + if (!(bootconsole->flags & CON_BOOT)) + bootconsole = NULL; + } + if (console_drivers->flags & CON_BOOT) bootconsole = console_drivers; } @@ -1195,15 +1210,32 @@ if (!(console->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); + if (bootconsole && (console->flags & CON_CONSDEV) && + !(console->flags & CON_BOOT)) { + /* 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 (bootconsole = console_drivers; bootconsole != NULL; + bootconsole = bootconsole->next) { + if (bootconsole->flags & CON_BOOT) + printk("boot [%s%d] ", bootconsole->name, + bootconsole->index); + } + printk(" -> real [%s%d]\n", console->name, console->index); + for (bootconsole = console_drivers; bootconsole != NULL; + bootconsole = bootconsole->next) { + if (bootconsole->flags & CON_BOOT) + unregister_console(bootconsole); + } console->flags &= ~CON_PRINTBUFFER; } else { - printk(KERN_INFO "console [%s%d] enabled\n", - console->name, console->index); + if (console->flags & CON_BOOT) + printk(KERN_INFO "bootconsole [%s%d] enabled\n", + console->name, console->index); + else + printk(KERN_INFO "console [%s%d] enabled\n", + console->name, console->index); } /*
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