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

Greg KH gregkh at linuxfoundation.org
Mon Mar 2 03:33:49 UTC 2015

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 at microsoft.com>
> ---
>  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 k-h

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