RE: [PATCH 1/3] drivers:pnp Add support for descendants claiming memory address space

[KY Srinivasan]

> -----Original Message-----
> From: Greg KH [mailto:gregkh@xxxxxxxxxxxxxxxxxxx]
> Sent: Sunday, March 1, 2015 7:34 PM
> To: Jake Oshins
> Cc: rafael.j.wysocki@xxxxxxxxx; KY Srinivasan; linux-kernel@xxxxxxxxxxxxxxx;
> devel@xxxxxxxxxxxxxxxxxxxxxx; olaf@xxxxxxxxx; apw@xxxxxxxxxxxxx;
> vkuznets@xxxxxxxxxx
> Subject: Re: [PATCH 1/3] drivers:pnp Add support for descendants claiming
> memory address space
> 
> On Tue, Feb 17, 2015 at 11:41:49AM -0800, Jake Oshins wrote:
> > This patch adds some wrapper functions in the pnp layer.  The intent
> > is to allow memory address space claims by devices which are
> > descendants (a child or grandchild of) a device which is already part
> > of the pnp layer.  This allows a device to make a resource claim that
> > doesn't conflict with its "aunts" and "uncles."
> >
> > This is useful in a Hyper-V VM because some paravirtual "devices" need
> > memory-mapped I/O space, and their aunts and uncles can be PCI devices.
> > Furthermore, the hypervisor expresses the possible memory address
> > combinations for the devices in the VM through the ACPI namespace.
> > The paravirtual devices need to suballocate from the ACPI nodes, and
> > they need to avoid conflicting with choices that the Linux PCI code
> > makes about the PCI devices in the VM.
> >
> > It might seem like this should be done in the platform layer rather
> > than the pnp layer, but the platform layer assumes that the
> > configuration of the devices in the machine are static, or at least
> > expressed by firmware in a static fashion.  The nature of a Hyper-V VM
> > is that new devices can be added while the machine is running, and the
> > potential configurations for them are expressed as part of the
> > paravirtual communications channel.  This much more naturally aligns
> > with the pnp layer.
> >
> > Signed-off-by: Jake Oshins <jakeo@xxxxxxxxxxxxx>
> > ---
> >  drivers/pnp/Makefile     |   2 +-
> >  drivers/pnp/base.h       |   2 +
> >  drivers/pnp/core.c       |   1 +
> >  drivers/pnp/descendant.c | 117
> +++++++++++++++++++++++++++++++++++++++++++++++
> >  include/linux/pnp.h      |  23 ++++++++++
> >  5 files changed, 144 insertions(+), 1 deletion(-)  create mode 100644
> > drivers/pnp/descendant.c
> 
> At first glance, this looks ok.  Does it change the sysfs layout of hyperv
> devices?
> 
> also, I'd like KY to sign-off on it, verifying that he at least tested the series and
> it works for him.

Greg,

Dan had some comments that Jake will address and resend. Also, we are waiting for
Rafael to review this patch. 

Regards,

K. Y
> 
> thanks,
> 
> greg k-h
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