[PATCH v2 07/27] PCI: Add software-emulated host bridge

[Stephen Warren]

On 01/28/2013 01:18 PM, Arnd Bergmann wrote:
> On Monday 28 January 2013, Thomas Petazzoni wrote:
>> From: Thierry Reding <thierry.reding at avionic-design.de>
>>
>> [Thomas Petazzoni:
>>  - Simplify capabilities handling.
>>  - Move to a separate file.
>>  - Fix mask used when writing a 4 bytes value.]
>>
>> Signed-off-by: Thierry Reding <thierry.reding at avionic-design.de>
>> Signed-off-by: Thomas Petazzoni <thomas.petazzoni at free-electrons.com>
> 
> Not even a description why this is needed?
> 
> This patch (together with patch 8) seems like the most controversial
> one of the series, so you should better provide a really good reason
> why we would emulate something in software rather than using whatever
> hardware is there.

At least on Tegra, there is no HW that exposes PCI configuration
registers for the host bridge itself. Only the root ports have exposed
PCI configuration registers. There was some debate re: whether a host
bridge device needed to exist or not. This patch makes such a device
exist if it's required.