Dynamic switch from Console on ttyS0 to fbcon

4 messages, 2 authors, 2008-08-22 · open the first message on its own page

Dynamic switch from Console on ttyS0 to fbcon

From: Amol Lad <hidden>
Date: 2008-08-20 04:18:46

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

From: Geert Uytterhoeven <geert@linux-m68k.org>
Date: 2008-08-20 06:51:38

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

From: Amol Lad <hidden>
Date: 2008-08-20 07:16:33

On Wed, Aug 20, 2008 at 12:21 PM, Geert Uytterhoeven
[off-list ref] wrote:
On Wed, 20 Aug 2008, Amol Lad wrote:
quoted
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
-------------------------------------------------------------------------
This SF.Net email is sponsored by the Moblin Your Move Developer's challenge
Build the coolest Linux based applications with Moblin SDK & win great prizes
Grand prize is a trip for two to an Open Source event anywhere in the world
http://moblin-contest.org/redirect.php?banner_id=100&url=/

Re: Dynamic switch from Console on ttyS0 to fbcon

From: Amol Lad <hidden>
Date: 2008-08-22 07:23:00

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 [off-list ref] wrote:
On Wed, Aug 20, 2008 at 12:21 PM, Geert Uytterhoeven
[off-list ref] wrote:
quoted
On Wed, 20 Aug 2008, Amol Lad wrote:
quoted
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.
quoted
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
quoted
Gr{oetje,eeting}s,
Thanks
Amol
quoted
                                               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
-------------------------------------------------------------------------
This SF.Net email is sponsored by the Moblin Your Move Developer's challenge
Build the coolest Linux based applications with Moblin SDK & win great prizes
Grand prize is a trip for two to an Open Source event anywhere in the world
http://moblin-contest.org/redirect.php?banner_id=100&url=/
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