Re: [PATCH v3] dt-bindings: pmem: Convert binding to YAML

[Drew Fustini <drew@pdp7.com>]

On Mon, Jun 09, 2025 at 08:32:41AM -0500, Rob Herring wrote:
> On Fri, Jun 06, 2025 at 11:11:17AM -0700, Drew Fustini wrote:
> > Convert the PMEM device tree binding from text to YAML. This will allow
> > device trees with pmem-region nodes to pass dtbs_check.
> > 
> > Acked-by: Conor Dooley <conor.dooley@microchip.com>
> > Acked-by: Oliver O'Halloran <oohall@gmail.com>
> > Signed-off-by: Drew Fustini <drew@pdp7.com>
> > ---
> > Dan/Dave/Vishal: does it make sense for this pmem binding patch to go
> > through the nvdimm tree?
> > 
> > Note: checkpatch complains about "DT binding docs and includes should
> > be a separate patch". Rob told me that this a false positive. I'm hoping
> > that I can fix the false positive at some point if I can remember enough
> > perl :)
> > 
> > v3:
> >  - no functional changes
> >  - add Oliver's Acked-by
> >  - bump version to avoid duplicate message-id mess in v2 and v2 resend:
> >    https://lore.kernel.org/all/20250520021440.24324-1-drew@pdp7.com/
> > 
> > v2 resend:
> >  - actually put v2 in the Subject
> >  - add Conor's Acked-by
> >    - https://lore.kernel.org/all/20250520-refract-fling-d064e11ddbdf@spud/
> > 
> > v2:
> >  - remove the txt file to make the conversion complete
> >  - https://lore.kernel.org/all/20250520021440.24324-1-drew@pdp7.com/
> > 
> > v1:
> >  - https://lore.kernel.org/all/20250518035539.7961-1-drew@pdp7.com/
> > 
> >  .../devicetree/bindings/pmem/pmem-region.txt  | 65 -------------------
> >  .../devicetree/bindings/pmem/pmem-region.yaml | 49 ++++++++++++++
> >  MAINTAINERS                                   |  2 +-
> >  3 files changed, 50 insertions(+), 66 deletions(-)
> >  delete mode 100644 Documentation/devicetree/bindings/pmem/pmem-region.txt
> >  create mode 100644 Documentation/devicetree/bindings/pmem/pmem-region.yaml
> > 
> > diff --git a/Documentation/devicetree/bindings/pmem/pmem-region.txt b/Documentation/devicetree/bindings/pmem/pmem-region.txt
> > deleted file mode 100644
> > index cd79975e85ec..000000000000
> > --- a/Documentation/devicetree/bindings/pmem/pmem-region.txt
> > +++ /dev/null
> > @@ -1,65 +0,0 @@
> > -Device-tree bindings for persistent memory regions
> > ------------------------------------------------------
> > -
> > -Persistent memory refers to a class of memory devices that are:
> > -
> > -	a) Usable as main system memory (i.e. cacheable), and
> > -	b) Retain their contents across power failure.
> > -
> > -Given b) it is best to think of persistent memory as a kind of memory mapped
> > -storage device. To ensure data integrity the operating system needs to manage
> > -persistent regions separately to the normal memory pool. To aid with that this
> > -binding provides a standardised interface for discovering where persistent
> > -memory regions exist inside the physical address space.
> > -
> > -Bindings for the region nodes:
> > ------------------------------
> > -
> > -Required properties:
> > -	- compatible = "pmem-region"
> > -
> > -	- reg = <base, size>;
> > -		The reg property should specify an address range that is
> > -		translatable to a system physical address range. This address
> > -		range should be mappable as normal system memory would be
> > -		(i.e cacheable).
> > -
> > -		If the reg property contains multiple address ranges
> > -		each address range will be treated as though it was specified
> > -		in a separate device node. Having multiple address ranges in a
> > -		node implies no special relationship between the two ranges.
> > -
> > -Optional properties:
> > -	- Any relevant NUMA associativity properties for the target platform.
> > -
> > -	- volatile; This property indicates that this region is actually
> > -	  backed by non-persistent memory. This lets the OS know that it
> > -	  may skip the cache flushes required to ensure data is made
> > -	  persistent after a write.
> > -
> > -	  If this property is absent then the OS must assume that the region
> > -	  is backed by non-volatile memory.
> > -
> > -Examples:
> > ---------------------
> > -
> > -	/*
> > -	 * This node specifies one 4KB region spanning from
> > -	 * 0x5000 to 0x5fff that is backed by non-volatile memory.
> > -	 */
> > -	pmem@5000 {
> > -		compatible = "pmem-region";
> > -		reg = <0x00005000 0x00001000>;
> > -	};
> > -
> > -	/*
> > -	 * This node specifies two 4KB regions that are backed by
> > -	 * volatile (normal) memory.
> > -	 */
> > -	pmem@6000 {
> > -		compatible = "pmem-region";
> > -		reg = < 0x00006000 0x00001000
> > -			0x00008000 0x00001000 >;
> > -		volatile;
> > -	};
> > -
> > diff --git a/Documentation/devicetree/bindings/pmem/pmem-region.yaml b/Documentation/devicetree/bindings/pmem/pmem-region.yaml
> > new file mode 100644
> > index 000000000000..a4aa4ce3318b
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/pmem/pmem-region.yaml
> > @@ -0,0 +1,49 @@
> > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/pmem-region.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +maintainers:
> > +  - Bjorn Helgaas <bhelgaas@google.com>
> 
> Drop Bjorn. He only did typo fixes on this.
> 
> > +  - Oliver O'Halloran <oohall@gmail.com>
> > +
> > +title: Persistent Memory Regions
> > +
> > +description: |
> > +  Persistent memory refers to a class of memory devices that are:
> > +
> > +    a) Usable as main system memory (i.e. cacheable), and
> > +    b) Retain their contents across power failure.
> > +
> > +  Given b) it is best to think of persistent memory as a kind of memory mapped
> > +  storage device. To ensure data integrity the operating system needs to manage
> > +  persistent regions separately to the normal memory pool. To aid with that this
> > +  binding provides a standardised interface for discovering where persistent
> > +  memory regions exist inside the physical address space.
> > +
> > +properties:
> > +  compatible:
> > +    const: pmem-region
> > +
> > +  reg:
> > +    maxItems: 1
> > +
> > +  volatile:
> > +    description: |
> 
> Don't need '|' here.

Rob - Thanks for the feedback. Should I send a new revision with these
two changes?

Drew