Re: Dell Media Direct button

[Javier Martín]

2008/8/21 Stefan Reinauer <address@hidden>:
> Robert Millan wrote:
>> On Wed, Aug 20, 2008 at 10:57:22AM +0200, Per Öberg wrote:
>>
>>> Hi
>>>
>>> Some laptops, e.g., from Dell have a special button that they use to
>>> boot a special embedded OS for media only instead of the ordinary OS.
>>>
>>> For my Dell XPS1330M I can determine if the Media button was pressed by
>>> first writing 0xf9 to port 0x70 and then testing bit 0x08 of port 0x71.
>>>
>>> It would be really nice if such a test could be enabled in grub so that
>>> grub can go directly to a specific menu alternative without showing the
>>> gui if the media button was pressed.
>>>
>>> Is this interesting? I'd like to contribute but I don't know where to start.
>>>
>>
>> Sounds interesting, but this needs some thought on how to design it.
>>
>> I suppose what you want is change the 'default' variable.  Perhaps increase
>> it by 1?  But then, where do you do this?  grub_machine_init is too early as
>> 'default' hasn't been set yet.
>>
>> Maybe we could have a global 'int default_offset' variable that is 
>> initialized
>> in grub_machine_init and later on used by normal.mod?
>>
>>
>
> The sequence of writing to port 0x70 / reading from port 0x71 reflects
> reading from the computer's "cmos" nvram memory.
> bit 7 of 0x70 is reserved for disabling NMIs, so the actual information
> is stored in byte 0x79[8] in the cmos.
>
> To allow full flexibility, there should just be a module that allows
> reading / writing the cmos values (could also be useful for other
> things, such as reading a boot order set by the bios).
>
> Everything else makes more sense in scripting:
> - changing "default"
> - changing "timeout"
> - support for bit operations in the parser
> - etc...
>
> --
> coresystems GmbH • Brahmsstr. 16 • D-79104 Freiburg i. Br.
>      Tel.: +49 761 7668825 • Fax: +49 761 7664613
> Email: address@hidden  • http://www.coresystems.de/
> Registergericht: Amtsgericht Freiburg • HRB 7656
> Geschäftsführer: Stefan Reinauer • Ust-IdNr.: DE245674866
>
>
>
> _______________________________________________
> Grub-devel mailing list
> address@hidden
> http://lists.gnu.org/mailman/listinfo/grub-devel
>

So what about a new "nvram" module in i386-pc that creates a variable
$NVRAM hooked to routines getting/setting the live contents of the
cmos memory? Then menu scripts can check its contents, among them the
MediaDirect button.

-Habbit