Re: [gentoo-user] dummy console

[Richard Fish <bigfish@asmallpond.org>]

Jorge Almeida wrote:

> On Mon, 25 Jul 2005, Richard Fish wrote:
>
>>
>>
>> Jorge Almeida wrote:
>>
>>> I upgraded from kernel 2.6.11 (gentoo-sources r4) to 2.6.12 (r6), and
>>> lost my framebuffer console. No console whatsoever, actually, but xdm
>>> starts OK. Checking .config, I see
>>>     # Console display driver support
>>>     #
>>>     CONFIG_VGA_CONSOLE=y
>>>     CONFIG_DUMMY_CONSOLE=y
>>>     CONFIG_FRAMEBUFFER_CONSOLE=m
>>
>>
>>
>> Oh, and also, FRAMEBUFFER_CONSOLE should be =y
>>
> Will try that (only tomorrow night, I can't access my home box until
> then).
> Still, what about the "dummy" thing? The configurator doesn't give a
> chance. Is it OK like this?
>

Seems ok (I have the same thing).  Looking at the Kconfig file in 
drivers/video/console, I find:


config VGA_CONSOLE
        bool "VGA text console" if EMBEDDED || !X86
        depends on !ARCH_ACORN && !ARCH_EBSA110 && !4xx && !8xx && 
!SPARC32 && !SPARC64 && !M68K && !PARISC
        default y
[...]

Which means that VGA_CONSOLE is only configurable if you are doing an 
EMBEDDED or non-x86 configuration.  For normal x86 builds, VGA_CONSOLE 
will always be available, since it defaults to 'y'

Later on, we find:

config DUMMY_CONSOLE
        bool
        depends on PROM_CONSOLE!=y || VGA_CONSOLE!=y || 
SGI_NEWPORT_CONSOLE!=y
        default y

There seems to be a bit of a hole in the logic here, becuase 
PROM_CONSOLE is only configurable if you are on SPARC, and 
SGI_NEWPORT_CONSOLE is only configurable if you are on an SGI.  So on 
x86, you are guaranteed both that VGA_CONSOLE will be =y, which means 
the middle conditional fails, but both of the other conditionals are 
true, so the whole statement is true.  So you will get DUMMY_CONSOLE, 
and you will not have a chance to configure it since there is no title 
after the "bool".

-Richard

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