Dynamic switch from Console on ttyS0 to fbcon

Dynamic switch from Console on ttyS0 to fbcon

[Amol Lad]

Hi,

I'm trying to switch the console from ttyS0 to frame buffer. This is
achieved using fbcon; you can either link it statically in kernel or
"modprobe fbcon" (Documentation/fb/fbcon.txt)

The problem is if "console=ttyS0,115200n8" is passed on u-boot command
line then the console switch to framebuffer does not happen after
doing modprobe fbcon.

If "console=ttyS0,115200n8" argument is not passed on u-boot then the
console switch happens after modprobe fbcon.

Any ideas why switch does not happen when "console=" argument is
passed to the kernel ? (In my application, I need to switch the
console dynamically to framebuffer from ttyS0. This decision cannot be
done in u-boot so u-boot will pass "console=ttyS0,115200n8" argument)

Thanks
Amol

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Re: Dynamic switch from Console on ttyS0 to fbcon

[Geert Uytterhoeven]

On Wed, 20 Aug 2008, Amol Lad wrote:
> I'm trying to switch the console from ttyS0 to frame buffer. This is
> achieved using fbcon; you can either link it statically in kernel or
> "modprobe fbcon" (Documentation/fb/fbcon.txt)
> 
> The problem is if "console=ttyS0,115200n8" is passed on u-boot command
> line then the console switch to framebuffer does not happen after
> doing modprobe fbcon.
> 
> If "console=ttyS0,115200n8" argument is not passed on u-boot then the
> console switch happens after modprobe fbcon.
> 
> Any ideas why switch does not happen when "console=" argument is
> passed to the kernel ? (In my application, I need to switch the
> console dynamically to framebuffer from ttyS0. This decision cannot be
> done in u-boot so u-boot will pass "console=ttyS0,115200n8" argument)

Have you tried

    console=ttyS0,115200n8 console=tty0

? This will make console output go to both, and console input will come
from tty0.

Gr{oetje,eeting}s,

						Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
							    -- Linus Torvalds

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Re: Dynamic switch from Console on ttyS0 to fbcon

[Amol Lad]

On Wed, Aug 20, 2008 at 12:21 PM, Geert Uytterhoeven
<geert@linux-m68k.org> wrote:
> On Wed, 20 Aug 2008, Amol Lad wrote:
>> I'm trying to switch the console from ttyS0 to frame buffer.
>>
>> The problem is if "console=ttyS0,115200n8" is passed on u-boot command
>> line then the console switch to framebuffer does not happen after
>> doing modprobe fbcon.
>>
>> If "console=ttyS0,115200n8" argument is not passed on u-boot then the
>> console switch happens after modprobe fbcon.
>>

> Have you tried
>
>    console=ttyS0,115200n8 console=tty0
>
> ? This will make console output go to both, and console input will come
> from tty0.

I tried that. This makes user space to use tty0 as /dev/console. In
this case I did "modprobe fbcon" (from telnet session) and I get
console on FB.
But I want console to stay on ttyS0 if "modprobe fbcon" is not done.
This way based on some /proc entry I can decide to switch to frame
buffer console in startup script or stay in ttyS0 mode

>
> Gr{oetje,eeting}s,

Thanks
Amol

>
>                                                Geert
>
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
>
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
>                                                            -- Linus Torvalds
>

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Re: Dynamic switch from Console on ttyS0 to fbcon

[Amol Lad]

well.... very easy solution

1. Pass console=ttyS0 command line
2. modprobe fbcon
3. a.out 1>/dev/tty0 2>/dev/tty0

So, now all outs from a.out will come on FB

thanks

On Wed, Aug 20, 2008 at 12:46 PM, Amol Lad <amol.lad@gmail.com> wrote:
> On Wed, Aug 20, 2008 at 12:21 PM, Geert Uytterhoeven
> <geert@linux-m68k.org> wrote:
>> On Wed, 20 Aug 2008, Amol Lad wrote:
>>> I'm trying to switch the console from ttyS0 to frame buffer.
>>>
>>> The problem is if "console=ttyS0,115200n8" is passed on u-boot command
>>> line then the console switch to framebuffer does not happen after
>>> doing modprobe fbcon.
>>>
>>> If "console=ttyS0,115200n8" argument is not passed on u-boot then the
>>> console switch happens after modprobe fbcon.
>>>
>
>> Have you tried
>>
>>    console=ttyS0,115200n8 console=tty0
>>
>> ? This will make console output go to both, and console input will come
>> from tty0.
>
> I tried that. This makes user space to use tty0 as /dev/console. In
> this case I did "modprobe fbcon" (from telnet session) and I get
> console on FB.
> But I want console to stay on ttyS0 if "modprobe fbcon" is not done.
> This way based on some /proc entry I can decide to switch to frame
> buffer console in startup script or stay in ttyS0 mode
>
>>
>> Gr{oetje,eeting}s,
>
> Thanks
> Amol
>
>>
>>                                                Geert
>>
>> --
>> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
>>
>> In personal conversations with technical people, I call myself a hacker. But
>> when I'm talking to journalists I just say "programmer" or something like that.
>>                                                            -- Linus Torvalds
>>
>

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