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

From: Jes Sorensen <Jes.Sorensen@redhat.com>
To: Greg KH <gregkh@linuxfoundation.org>
Cc: David Kershner <david.kershner@unisys.com>,
	corbet@lwn.net, tglx@linutronix.de, mingo@redhat.com,
	hpa@zytor.com, erik.arfvidson@unisys.com,
	timothy.sell@unisys.com, hofrat@osadl.org, dzickus@redhat.com,
	alexander.curtin@unisys.com, janani.rvchndrn@gmail.com,
	sudipm.mukherjee@gmail.com, prarit@redhat.com,
	david.binder@unisys.com, nhorman@redhat.com,
	dan.j.williams@intel.com, linux-kernel@vger.kernel.org,
	linux-doc@vger.kernel.org,
	driverdev-devel@linuxdriverproject.org,
	sparmaintainer@unisys.com
Subject: Re: [PATCH 0/5] add bus driver for Unisys s-Par paravirtualized devices to arch/x86
Date: Tue, 17 May 2016 19:49:53 -0400	[thread overview]
Message-ID: <wrfjr3d0453y.fsf@redhat.com> (raw)
In-Reply-To: <20160517142735.GA19617@kroah.com> (Greg KH's message of "Tue, 17 May 2016 07:27:35 -0700")

Greg KH <gregkh@linuxfoundation.org> writes:
> On Tue, May 17, 2016 at 10:01:55AM -0400, Jes Sorensen wrote:
>> Greg KH <gregkh@linuxfoundation.org> 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.
>
> Ok, but still no need to put it under arch/ anything, it should go in
> drivers/ like all other drivers and busses are, no matter what the arch
> it happens to run on is.

I don't think thats obvious. arch/x86/kvm is an example of this, Sparc
and PPC also have their stuff under arch/.

I am open, if people prefer to have drivers/visorbus I can support that.
I find right now it's really messy with things being put all over the
place, and it's not obvious what the real placement is for all of this.

Jes