On Thu, Dec 03, 2015 at 06:02:09PM -0800, Brian Norris wrote:
> As noted here [1], there are potentially future conflicts if we try to
> use MTD's "partitions" subnode to describe anything besides just the
> fixed-in-the-device-tree partitions currently described in this
> document. Particularly, there was a proposal to use this node for the
> AFS parser too.
>
> It can pose a (small) problem to try to differentiate the following
> nodes:
>
> // using binding as currently specified
> partitions {
> #address-cells = <x>;
> #size-cells = <y>;
> partition@0 {
> ...;
> };
> };
>
> and
>
> // proposed future binding
> partitions {
> compatible = "arm,arm-flash-structure";
> };
>
> It's especially difficult if other uses of this node start having
> subnodes.
>
> So, since the "partitions" node is new in v4.4, let's fixup the binding
> before release so that it requires a compatible property, so it's much
> clearer to distinguish. e.g.:
>
> // proposed
> partitions {
> compatible = "partitions";
> #address-cells = <x>;
> #size-cells = <y>;
> partition@0 {
> ...;
> };
> };
>
> [1] Subject: "mtd: create a partition type device tree binding"
> http://lkml.kernel.org/g/20151113220039.GA74382@xxxxxxxxxx
> http://lists.infradead.org/pipermail/linux-mtd/2015-November/063355.html
> http://lists.infradead.org/pipermail/linux-mtd/2015-November/063364.html
>
> Cc: Michal Suchanek <hramrach@xxxxxxxxx>
> Signed-off-by: Brian Norris <computersforpeace@xxxxxxxxx>
> ---
> This one is more of a future proofing patch. We should probably take this for
> 4.4, before the binding "stabilizes" (I don't actually see any users yet), or
> else we'll have to find some other (possibly more complicated) way to avoid
> this potential collision on future development.
Acked-by: Rob Herring <robh@xxxxxxxxxx>
>
> Documentation/devicetree/bindings/mtd/partition.txt | 7 ++++++-
> drivers/mtd/ofpart.c | 3 +++
> 2 files changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/devicetree/bindings/mtd/partition.txt b/Documentation/devicetree/bindings/mtd/partition.txt
> index f1e2a02381a4..047e80575881 100644
> --- a/Documentation/devicetree/bindings/mtd/partition.txt
> +++ b/Documentation/devicetree/bindings/mtd/partition.txt
> @@ -6,7 +6,9 @@ used for what purposes, but which don't use an on-flash partition table such
> as RedBoot.
>
> The partition table should be a subnode of the mtd node and should be named
> -'partitions'. Partitions are defined in subnodes of the partitions node.
> +'partitions'. This node should have the following property:
> +- compatible : (required) must be "partitions"
> +Partitions are then defined in subnodes of the partitions node.
>
> For backwards compatibility partitions as direct subnodes of the mtd device are
> supported. This use is discouraged.
> @@ -36,6 +38,7 @@ Examples:
>
> flash@0 {
> partitions {
> + compatible = "partitions";
> #address-cells = <1>;
> #size-cells = <1>;
>
> @@ -53,6 +56,7 @@ flash@0 {
>
> flash@1 {
> partitions {
> + compatible = "partitions";
> #address-cells = <1>;
> #size-cells = <2>;
>
> @@ -66,6 +70,7 @@ flash@1 {
>
> flash@2 {
> partitions {
> + compatible = "partitions";
> #address-cells = <2>;
> #size-cells = <2>;
>
> diff --git a/drivers/mtd/ofpart.c b/drivers/mtd/ofpart.c
> index 3e9c5857c991..23cd809fad4c 100644
> --- a/drivers/mtd/ofpart.c
> +++ b/drivers/mtd/ofpart.c
> @@ -55,6 +55,9 @@ static int parse_ofpart_partitions(struct mtd_info *master,
> master->name, mtd_node->full_name);
> ofpart_node = mtd_node;
> dedicated = false;
> + } else if (!of_device_is_compatible(ofpart_node, "partitions")) {
> + /* The 'partitions' subnode might be used by another parser */
> + return 0;
> }
>
> /* First count the subnodes */
> --
> 2.6.0.rc2.230.g3dd15c0
>
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