Re: [PATCH 0/5] add bus driver for Unisys s-Par paravirtualized devices to arch/x86

[Jes Sorensen]

Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> writes:
> On Tue, May 17, 2016 at 03:27:56AM -0400, David Kershner wrote:
>> This patchset moves the visorbus driver (fromdrivers/staging/unisys/visorbus)
>> and its dependent headers files (from drivers/staging/unisys/include)
>> out of staging into the main kernel tree.
>> 
>> The visorbus driver is a bus driver for various paravirtualized devices
>> presented within a Unisys s-Par guest environment.  Drivers for these
>> devices are also currently present under drivers/staging/unisys/, which we
>> intend to also move out of staging immediately after visorbus.  All of
>> these other drivers are dependent upon visorbus and the include directory,
>> which is why we would like to move these first.
>> 
>> Our initial consultations with various members of the community have led us
>> to the conclusion that the most appropriate locations for these is:
>>     arch/x86/visorbus/       (driver)
>>     include/linux/visorbus/  (header files)
>> 
>> The rationale is that visorbus is dependent on x86-64 architecture.
>
> What makes it dependent on x86?  What prevents it from running on some
> other architecture (not the fact that no one has made such hardware,
> just the code reasons please.)

It's dependent on system firmware which is only available on the S-Par
platform which is x86_64 only. The closest similarity is probably what
you find on the PPC and Sparc platforms.

Jes