linux-kernel - Re: [PATCH 1/1] x86: Add config option to setup early serial console

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Message-ID: <4851AAAD.8050105@sgi.com>
Date:	Thu, 12 Jun 2008 16:01:01 -0700
From:	Mike Travis <travis@....com>
To:	Yinghai Lu <yhlu.kernel@...il.com>
CC:	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] x86: Add config option to setup early serial console

Yinghai Lu wrote:
> On Thu, Jun 12, 2008 at 3:42 PM, Mike Travis <travis@....com> wrote:
>>  * Add config option EARLY_SERIAL_CONSOLE to enable early
>>   printk's to be directed to the serial console.
>>
>> Based on linux-next
>>
>> Signed-off-by: Mike Travis <travis@....com>
>> ---
>>
>> ---
>>  arch/x86/Kconfig.debug         |    9 +++++++++
>>  arch/x86/kernel/early_printk.c |    4 ++++
>>  2 files changed, 13 insertions(+)
>>
>> --- linux-2.6-next.orig/arch/x86/Kconfig.debug
>> +++ linux-2.6-next/arch/x86/Kconfig.debug
>> @@ -29,6 +29,15 @@ config EARLY_PRINTK
>>          with klogd/syslogd or the X server. You should normally N here,
>>          unless you want to debug such a crash.
>>
>> +config EARLY_SERIAL_CONSOLE
>> +       bool "Early Serial Console"
>> +       default n
>> +       help
>> +         Initializes the early console to be the serial port.  The default
>> +         is to use the VGA console.
>> +
>> +         This is useful for server systems that do not have a VGA console.
>> +
>>  config DEBUG_STACKOVERFLOW
>>        bool "Check for stack overflows"
>>        depends on DEBUG_KERNEL
>> --- linux-2.6-next.orig/arch/x86/kernel/early_printk.c
>> +++ linux-2.6-next/arch/x86/kernel/early_printk.c
>> @@ -193,7 +193,11 @@ static struct console simnow_console = {
>>  };
>>
>>  /* Direct interface for emergencies */
>> +#ifdef CONFIG_EARLY_SERIAL_CONSOLE
>> +static struct console *early_console = &early_serial_console;
>> +#else
>>  static struct console *early_console = &early_vga_console;
>> +#endif
>>  static int early_console_initialized;
>>
>>  void early_printk(const char *fmt, ...)
>>
> 
> can you check if it can work with
> console=uart8250,io,0x3f8,115200
> 
> that is early console, and will switch to normal console automatically
> 
> YH

I'll rework the patch to enable the serial console as early as possible.
Currently, it's done quite a ways down in start_kernel().

Thanks,
Mike
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