Date:	Mon, 6 Jun 2011 19:04:40 -0400
From:	Chris Metcalf <cmetcalf@...era.com>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
CC:	Arnd Bergmann <arnd@...db.de>, Timur Tabi <timur@...escale.com>,
	Deepak Saxena <dsaxena@...aro.org>, <kumar.gala@...escale.com>,
	<benh@...nel.crashing.org>, <greg@...ah.com>, <akpm@...nel.org>,
	<linuxppc-dev@...ts.ozlabs.org>, <linux-kernel@...r.kernel.org>,
	<linux-console@...r.kernel.org>
Subject: Re: [PATCH 7/7] [v2] drivers/misc: introduce Freescale hypervisor
 management driver

For context, the most recent patch for the tile driver in question is here:

https://patchwork.kernel.org/patch/843892/

On 6/6/2011 5:23 PM, Konrad Rzeszutek Wilk wrote:
> On Mon, Jun 06, 2011 at 05:01:36PM -0400, Chris Metcalf wrote:
>> On 6/6/2011 12:24 PM, Arnd Bergmann wrote:
>>> On Monday 06 June 2011, Timur Tabi wrote:.
>>>> And what about my concern that my driver will be the only one in drivers/virt?
>>> I have no doubt that more of these will come. Chris Metcalf is currently
>>> looking for a home for his tilera hypervisor drivers, and we have the
>>> microsoft hyperv drivers in drivers/staging, so they will hopefully
>>> move to a proper place later. We also have similar drivers in other
>>> places, e.g. drivers/ps3/ps3-sys-manager.c, drivers/s390/char/vmcp.c
>>> or parts of drivers/xen.
>> It might help if someone (Arnd?) wanted to propose a statement of what
>> drivers/virt was really for.  If it's for any Linux driver that upcalls to
> Was for? I am not seeing it in v3.0-rc2?

Sorry, maybe a questionable idiom, but please read past tense in the quoted
text as meaning present tense :-)

>> a hypervisor for any reason, then the Tilera paravirtualized drivers fit in
>> well.  If it's intended more for drivers that guests running under a
>> hypervisor can use to talk to the hypervisor itself (e.g. managing
> I believe that the code that deals with specific subsystem (so block API
> for example) would reside in subsystem directory (so drivers/block would have
> your virtualization block driver). This allows the maintainer of block
> to make sure your driver is OK.

Sure, makes sense.  The new push (as I understand it) is to group primarily
by function, not by bus or architecture.

>> notifications that a hypervisor delivers to a guest to cause it to shut
>> down or take other actions), then it doesn't seem like the Tilera
> That looks to be arch/<x>/tilera/virt/ candidate?

Arnd, among others, has suggested that all drivers live in "drivers"
somewhere, so "arch/tile" may not be the best place.  (To be fair, I
originally had this driver in arch/tile/drivers/, so your idea is certainly
reasonable!)

>> paravirtualized device drivers belong there, since they're just using the
>> Tilera hypervisor synchronously to do I/O or get/set device and driver state.
> Well, I/O sounds like block API or network API. But then you are also
> doing management ioctl - which implies "drivers". "drivers/tilera" does not
> work?

There is certainly precedent for drivers that don't fit cleanly into an
existing category to go in drivers/<arch>, e.g. drivers/s390,
drivers/parisc, etc.  There is also drivers/platform/x86, though that seems
to be for the bus "platform drivers" rather than just a random character
driver like the one in question.

I don't have a particular opinion here; I'm just hoping to develop enough
consensus that I can ask Linus to pull the driver without generating
controversy :-)

-- 
Chris Metcalf, Tilera Corp.
http://www.tilera.com


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