[coreboot] [RFC] kill unwanted_vpci, use "hidden" property instead

[Carl-Daniel Hailfinger]

Ron/Stefan?

I'm not sure if we can perform generic hiding of devices behind a
bridge. Could you look at the mail below?

Thanks!
Carl-Daniel

On 08.05.2008 18:06, Carl-Daniel Hailfinger wrote:
> On 08.05.2008 17:14, Stefan Reinauer wrote:
>   
>> ron minnich wrote:
>>   
>>     
>>> On Thu, May 8, 2008 at 7:51 AM, Stefan Reinauer <stepan at coresystems.de> wrote:
>>>
>>>       
> Are devices behind a disabled bridge completely invisible or do their
> PCI headers show up?
>
>   
>> I can't find any bridge in v2 from a quick scan that would stay un-enabled.
>>
>> If we don't know whether the OS wants the device, we enable it, not
>> leave it or disable it.
>>
>> We disable or hide the device, if that functionality is not there on the
>> _board_, ie. because it is not wired.
>>   
>>     
>
> Commerical BIOS sometimes have the ability to disable/hide otherwise
> functional onboard devices, which is useful if the machine is severely
> resource constrained in the IRQ area and/or the user doesn't want the OS
> to drive the device.
>
>   
>> If we start thinking about what the OS wants in this context, we have to
>> call this ACPI and make distinctions between OSes in the DTS. ;-)
>>   
>>     
>
> Mind bleach! Now!
>
>   
>>> Look in pci_probe_dev for example: device is unconditionally enabled,
>>> so we can scan it.
>>>
>>> IIRC one case that drove this was multiple VGA cards -- you want to
>>> set up the BARs etc. for all but you really don't know what the OS
>>> will do -- maybe nothing -- but you want them there if it will do
>>> something.
>>>   
>>>     
>>>       
>> Unless the bios disables one of the devices, in which case the OS should
>> find nothing.
>>   
>>     
>
> What about devices which cause periodic interrupts once they are
> enabled? Enabling them has the undesirable effect of causing unhandled
> interrupts which irritate Linux a lot.
>
>   
>>> There really is a difference between un-enabled (or disabled) and
>>> hidden; as you pointed out, hidden means no config space, or "will not
>>> show up in lspci".
>>>   
>>>     
>>>       
>> So disabled devices do show up in lspci?
>>   
>>     
>
> I could try to dig up a lspci from a mail someone sent last year, but if
> Uwe has seen this on one of his machines, I'd be glad if he could track
> it down.
>