On 8/26/23 11:06, Sughosh Ganu wrote:
Add a document explaining the need for removal of non-compliant devicetree nodes and properties. Also describe in brief, the macros that can be used for this removal.
Signed-off-by: Sughosh Ganu sughosh.ganu@linaro.org
Thanks for properly documenting the change.
Warning, treated as error: doc/develop/devicetree/dt_non_compliant_purge.rst: document isn't included in any toctree
Please, add the document to doc/develop/devicetree/index.rst
Please, run make htmldocs before resubmitting.
.../devicetree/dt_non_compliant_purge.rst | 64 +++++++++++++++++++ 1 file changed, 64 insertions(+) create mode 100644 doc/develop/devicetree/dt_non_compliant_purge.rst
diff --git a/doc/develop/devicetree/dt_non_compliant_purge.rst b/doc/develop/devicetree/dt_non_compliant_purge.rst new file mode 100644 index 0000000000..c3a8feab5b --- /dev/null +++ b/doc/develop/devicetree/dt_non_compliant_purge.rst @@ -0,0 +1,64 @@ +.. SPDX-License-Identifier: GPL-2.0+
+Removal of non-compliant nodes and properties +=============================================
+The devicetree used in U-Boot might contain nodes and properties which +are specific only to U-Boot, and are not necessarily being used to +describe hardware but to pass information to U-Boot. An example of +such a property would be the public key being passed to U-Boot for +verification.
+This devicetree can then be passed to the OS. Since certain nodes and +properties are not really describing hardware, and more importantly, +these are only relevant to U-Boot, bindings for these cannot be +upstreamed into the devicetree repository. There have been instances +of attempts being made to upstream such bindings, and these deemed not
but these were not deemed fit
+fit for upstreaming. Not having a binding for these nodes and +properties means that the devicetree fails the schema compliance tests +[1]. This also means that the platform cannot get certifications like +SystemReady [2] which, among other things require a devicetree which
%s/require/requires/
+passes the schema compliance tests.
+For such nodes and properties, it has been suggested by the devicetree +maintainers that the right thing to do is to remove them from the
%s/that the right thing to do is//
+devicetree before it gets passed on to the OS [3].
%s/on to/to/
+Removing nodes/properties +-------------------------
+In U-Boot, this is been done through adding information on such nodes
%s/is been done through/is done by/
+and properties in a list. The entire node can be deleted, or a +specific property under a node can be deleted. The list of such nodes +and properties is generated at compile time, and the function to purge +these can be invoked through a EVT_FT_FIXUP event notify call.
+For deleting a node, this can be done by declaring a macro::
- DT_NON_COMPLIANT_PURGE(fwu_mdata) = {
.node_path = "/fwu-mdata",- };
Where should such a macro be placed?
+Similarly, for deleting a property under a node, that can be done by +specifying the property name::
- DT_NON_COMPLIANT_PURGE(capsule_key) = {
.node_path = "/signature",.prop = "capsule-key",- };
Why is capsule_key needed twice here? What would be the effect of:
DT_NON_COMPLIANT_PURGE(voodoo) = { .node_path = "/signature", .prop = "capsule-key", };
+In the first example, the entire node with path /fwu-mdata will be +removed. In the second example, the property capsule-key +under /signature node will be removed.
+Similarly, a list of nodes and properties can be specified using the +following macro::
- DT_NON_COMPLIANT_PURGE_LIST(foo) = {
What does foo refer to here? Can this parameter be eliminated from the syntax?
Will the application of the removals be sorted alphabetically by this argument?
What will happen if a property or node does not exist at time of removal? Hopefully that does not stop the boot process but is silently ignored.
{ .node_path = "/some_node", .prop = "some_bar" },{ .node_path = "/some_node" },- };
Why do you need the first element in your example? Wouldn't deleting /some/node imply that all its children are deleted?
Why do we need separate properties .node_path and .prop. It would be less effort to write:
DT_NON_COMPLIANT_PURGE_LIST() = { "/some_node_1/some_property_1", "/some_node_1/some_property_2", "/some_node_2", }
I assume the macro does its job irrespective of non-compliance. Why not call it DT_PURGE()?
Best regards
Heinrich
+[1] - https://github.com/devicetree-org/dt-schema +[2] - https://www.arm.com/architecture/system-architectures/systemready-certificat... +[3] - https://lore.kernel.org/u-boot/CAL_JsqJN4FeHomL7z3yj0WJ9bpx1oSE7zf26L_GV2oS6...