devicetree,xen: add xen,shared-memory binding

Introduce a device tree binding for Xen reserved-memory regions. They
are used to share memory across VMs from the VM config files. (See
static_shm config option.)
 
Signed-off-by: Stefano Stabellini <stefanos@xilinx.com>
Cc: julien.grall@arm.com

On Mon, Oct 08, 2018 at 04:03:54PM -0700, Stefano Stabellini wrote:
> Introduce a device tree binding for Xen reserved-memory regions. They
> are used to share memory across VMs from the VM config files. (See
> static_shm config option.)
>  
> Signed-off-by: Stefano Stabellini <stefanos@xilinx.com>

checkpatch.pl complains that the author and S-o-b don't match.

> Cc: julien.grall@arm.com
> 
> diff --git a/Documentation/devicetree/bindings/reserved-memory/xen,shared-memory.txt b/Documentation/devicetree/bindings/reserved-memory/xen,shared-memory.txt
> new file mode 100644
> index 0000000..a927a94
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/reserved-memory/xen,shared-memory.txt
> @@ -0,0 +1,20 @@
> +* Xen hypervisor reserved-memory binding
> +
> +Expose one or more memory regions as reserved-memory to the guest
> +virtual machine. Typically, a region is configured at VM creation time
> +to be a shared memory area across multiple virtual machines for
> +communication among them.
> +
> +For each of these pre-shared memory regions, a range is exposed under
> +the /reserved-memory node as a child node. Each range sub-node is named
> +xen-shmem@<address> and has the following properties:
> +
> +- compatible:
> +	compatible = xen,shared-memory"

Any need for versioning?

> +
> +- reg:
> +	the base guest physical address and size of the shared memory region
> +
> +- id:

xen,id

> +	a string that identifies the shared memory region as specified in
> +	the VM config file

On Wed, 17 Oct 2018, Rob Herring wrote:
> On Mon, Oct 08, 2018 at 04:03:54PM -0700, Stefano Stabellini wrote:
> > Introduce a device tree binding for Xen reserved-memory regions. They
> > are used to share memory across VMs from the VM config files. (See
> > static_shm config option.)
> >  
> > Signed-off-by: Stefano Stabellini <stefanos@xilinx.com>
> 
> checkpatch.pl complains that the author and S-o-b don't match.

I didn't know it wasn't allowed. I'll fix it.


> > Cc: julien.grall@arm.com
> > 
> > diff --git a/Documentation/devicetree/bindings/reserved-memory/xen,shared-memory.txt b/Documentation/devicetree/bindings/reserved-memory/xen,shared-memory.txt
> > new file mode 100644
> > index 0000000..a927a94
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/reserved-memory/xen,shared-memory.txt
> > @@ -0,0 +1,20 @@
> > +* Xen hypervisor reserved-memory binding
> > +
> > +Expose one or more memory regions as reserved-memory to the guest
> > +virtual machine. Typically, a region is configured at VM creation time
> > +to be a shared memory area across multiple virtual machines for
> > +communication among them.
> > +
> > +For each of these pre-shared memory regions, a range is exposed under
> > +the /reserved-memory node as a child node. Each range sub-node is named
> > +xen-shmem@<address> and has the following properties:
> > +
> > +- compatible:
> > +	compatible = xen,shared-memory"
> 
> Any need for versioning?

There is always need for versioning :-)
I'll send new patch with the following:

  compatible = "xen,shared-memory-v1", "xen,shared-memory"

> > +
> > +- reg:
> > +	the base guest physical address and size of the shared memory region
> > +
> > +- id:
> 
> xen,id

OK


> > +	a string that identifies the shared memory region as specified in
> > +	the VM config file
>