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    SubjectRe: [PATCH V4 6/6] dt-bindings: xen: Clarify "reg" purpose
    On Fri, 10 Dec 2021, Oleksandr Tyshchenko wrote:
    > From: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
    >
    > Xen on Arm has gained new support recently to calculate and report
    > extended regions (unused address space) safe to use for external
    > mappings. These regions are reported via "reg" property under
    > "hypervisor" node in the guest device-tree. As region 0 is reserved
    > for grant table space (always present), the indexes for extended
    > regions are 1...N.
    >
    > No device-tree bindings update is needed (except clarifying the text)
    > as guest infers the presence of extended regions from the number
    > of regions in "reg" property.
    >
    > Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>

    Acked-by: Stefano Stabellini <sstabellini@kernel.org>


    > ---
    > Changes V2 -> V3:
    > - new patch
    >
    > Changes V3 -> V4:
    > - add Stefano's R-b and Rob's A-b
    > - remove sentence about ACPI for "reg" and "interrupts"
    > properties
    >
    > Changes V4 -> V4.1
    > - bring the mentioning of ACPI back which, as was pointed out by Julien,
    > fits in the context:
    > https://lore.kernel.org/xen-devel/9602b019-6c20-cdc7-23f3-9e4f8fd720f6@xen.org/T/#t
    > so technically restore V3 state
    > - remove Stefano's R-b and Rob's A-b as I am not 100% sure they are
    > happy with that
    > ---
    > Documentation/devicetree/bindings/arm/xen.txt | 12 ++++++++----
    > 1 file changed, 8 insertions(+), 4 deletions(-)
    >
    > diff --git a/Documentation/devicetree/bindings/arm/xen.txt b/Documentation/devicetree/bindings/arm/xen.txt
    > index db5c56d..156fe10b 100644
    > --- a/Documentation/devicetree/bindings/arm/xen.txt
    > +++ b/Documentation/devicetree/bindings/arm/xen.txt
    > @@ -7,10 +7,14 @@ the following properties:
    > compatible = "xen,xen-<version>", "xen,xen";
    > where <version> is the version of the Xen ABI of the platform.
    >
    > -- reg: specifies the base physical address and size of a region in
    > - memory where the grant table should be mapped to, using an
    > - HYPERVISOR_memory_op hypercall. The memory region is large enough to map
    > - the whole grant table (it is larger or equal to gnttab_max_grant_frames()).
    > +- reg: specifies the base physical address and size of the regions in memory
    > + where the special resources should be mapped to, using an HYPERVISOR_memory_op
    > + hypercall.
    > + Region 0 is reserved for mapping grant table, it must be always present.
    > + The memory region is large enough to map the whole grant table (it is larger
    > + or equal to gnttab_max_grant_frames()).
    > + Regions 1...N are extended regions (unused address space) for mapping foreign
    > + GFNs and grants, they might be absent if there is nothing to expose.
    > This property is unnecessary when booting Dom0 using ACPI.
    >
    > - interrupts: the interrupt used by Xen to inject event notifications.
    > --
    > 2.7.4
    >

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