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.g...@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-certification-program
+[3] -
https://lore.kernel.org/u-boot/cal_jsqjn4fehoml7z3yj0wj9bpx1ose7zf26l_gv2os6cg-...@mail.gmail.com/
