One of the things we have tried to achieve with System Device Trees is to make sure we separate the HW description from the domain configuration that typically is done by a different person. That is, you don't want to have to edit or rewrite the parts that describes the HW in order to describe what memory, devices, cpus goes where.

Take an example where 2 cpus can either be configured to a) work together and see the same memory/devices (SMP for example), or b) be separated into two different domains running different OSes with different meory/devices.

So you have either one or two domains for those two cpus.

In this case I don't know that you want the "configurer" to have to go in and rewrite the file to use a different number of domains depending on the situation.

FWIW,

Tomas

On 1/21/20, 3:57 PM, "System-dt on behalf of Bjorn Andersson via System-dt" <system-dt-bounces@lists.openampproject.org on behalf of system-dt@lists.openampproject.org> wrote:

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On Tue 21 Jan 13:18 PST 2020, Rob Herring via System-dt wrote: [..] > To flip all this around, what if domains become the top-level structure: > > domain@0 { > chosen {}; > cpus {}; > memory@0 {}; > reserved-memory {}; > }; > > domain@1 { > chosen {}; > cpus {}; > memory@800000 {}; > reserved-memory {}; > }; >

I like this suggestion, as this both creates a natural grouping and could allow for describing domain-specific hardware as subtrees in each domain.

Regards, Bjorn

> The content of all the currently top-level nodes don't need to change. > The OS's would be modified to treat a domain node as the root node > which shouldn't be very invasive. Then everything else just works as > is. > > This could still have other nodes at the (real) root or links from one > domain to another. I haven't thought thru that part, but I think this > structure can only help because it removes the notion that the root > has a specific cpu view. > > Rob > -- > System-dt mailing list > System-dt@lists.openampproject.org > https://lists.openampproject.org/mailman/listinfo/system-dt -- System-dt mailing list System-dt@lists.openampproject.org https://lists.openampproject.org/mailman/listinfo/system-dt