[PATCH 07/12] docs: dt: convert of_unittest.txt to ReST

Mauro Carvalho Chehab
2020-03-02T07:38:51Z

- Adjust document and section titles;
- Adjust numerated list markups;
- Some whitespace fixes and new line breaks;
- Mark literal blocks as such;
- Add it to devicetree/index.rst.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
---
Documentation/devicetree/index.rst | 1 +
.../{of_unittest.txt => of_unittest.rst} | 186 +++++++++---------
2 files changed, 98 insertions(+), 89 deletions(-)
rename Documentation/devicetree/{of_unittest.txt => of_unittest.rst} (54%)

diff --git a/Documentation/devicetree/index.rst b/Documentation/devicetree/index.rst
index 308cac9d7021..ca83258fbba5 100644
--- a/Documentation/devicetree/index.rst
+++ b/Documentation/devicetree/index.rst
@@ -12,3 +12,4 @@ Open Firmware and Device Tree
booting-without-of
changesets
dynamic-resolution-notes
+ of_unittest
diff --git a/Documentation/devicetree/of_unittest.txt b/Documentation/devicetree/of_unittest.rst
similarity index 54%
rename from Documentation/devicetree/of_unittest.txt
rename to Documentation/devicetree/of_unittest.rst
index 9fdd2de9b770..dea05214f3ad 100644
--- a/Documentation/devicetree/of_unittest.txt
+++ b/Documentation/devicetree/of_unittest.rst
@@ -1,9 +1,13 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+==================================
Open Firmware Device Tree Unittest
-----------------------------------
+==================================

Author: Gaurav Minocha <gaurav.minocha.os@gmail.com>

1. Introduction
+===============

This document explains how the test data required for executing OF unittest
is attached to the live tree dynamically, independent of the machine's
@@ -11,8 +15,8 @@ architecture.

It is recommended to read the following documents before moving ahead.

-[1] Documentation/devicetree/usage-model.rst
-[2] http://www.devicetree.org/Device_Tree_Usage
+(1) Documentation/devicetree/usage-model.rst
+(2) http://www.devicetree.org/Device_Tree_Usage

OF Selftest has been designed to test the interface (include/linux/of.h)
provided to device driver developers to fetch the device information..etc.
@@ -21,79 +25,82 @@ most of the device drivers in various use cases.

2. Test-data
+============

The Device Tree Source file (drivers/of/unittest-data/testcases.dts) contains
the test data required for executing the unit tests automated in
drivers/of/unittest.c. Currently, following Device Tree Source Include files
-(.dtsi) are included in testcases.dts:
+(.dtsi) are included in testcases.dts::

-drivers/of/unittest-data/tests-interrupts.dtsi
-drivers/of/unittest-data/tests-platform.dtsi
-drivers/of/unittest-data/tests-phandle.dtsi
-drivers/of/unittest-data/tests-match.dtsi
+ drivers/of/unittest-data/tests-interrupts.dtsi
+ drivers/of/unittest-data/tests-platform.dtsi
+ drivers/of/unittest-data/tests-phandle.dtsi
+ drivers/of/unittest-data/tests-match.dtsi

-When the kernel is build with OF_SELFTEST enabled, then the following make rule
+When the kernel is build with OF_SELFTEST enabled, then the following make
+rule::

-$(obj)/%.dtb: $(src)/%.dts FORCE
- $(call if_changed_dep, dtc)
+ $(obj)/%.dtb: $(src)/%.dts FORCE
+ $(call if_changed_dep, dtc)

is used to compile the DT source file (testcases.dts) into a binary blob
(testcases.dtb), also referred as flattened DT.

After that, using the following rule the binary blob above is wrapped as an
-assembly file (testcases.dtb.S).
+assembly file (testcases.dtb.S)::

-$(obj)/%.dtb.S: $(obj)/%.dtb
- $(call cmd, dt_S_dtb)
+ $(obj)/%.dtb.S: $(obj)/%.dtb
+ $(call cmd, dt_S_dtb)

The assembly file is compiled into an object file (testcases.dtb.o), and is
linked into the kernel image.

2.1. Adding the test data
+-------------------------

Un-flattened device tree structure:

Un-flattened device tree consists of connected device_node(s) in form of a tree
-structure described below.
+structure described below::

-// following struct members are used to construct the tree
-struct device_node {
- ...
- struct device_node *parent;
- struct device_node *child;
- struct device_node *sibling;
- ...
- };
+ // following struct members are used to construct the tree
+ struct device_node {
+ ...
+ struct device_node *parent;
+ struct device_node *child;
+ struct device_node *sibling;
+ ...
+ };

Figure 1, describes a generic structure of machine's un-flattened device tree
considering only child and sibling pointers. There exists another pointer,
-*parent, that is used to traverse the tree in the reverse direction. So, at
+``*parent``, that is used to traverse the tree in the reverse direction. So, at
a particular level the child node and all the sibling nodes will have a parent
pointer pointing to a common node (e.g. child1, sibling2, sibling3, sibling4's
-parent points to root node)
+parent points to root node)::

-root ('/')
- |
-child1 -> sibling2 -> sibling3 -> sibling4 -> null
- | | | |
- | | | null
- | | |
- | | child31 -> sibling32 -> null
- | | | |
- | | null null
- | |
- | child21 -> sibling22 -> sibling23 -> null
- | | | |
- | null null null
- |
-child11 -> sibling12 -> sibling13 -> sibling14 -> null
- | | | |
- | | | null
- | | |
- null null child131 -> null
- |
- null
+ root ('/')
+ |
+ child1 -> sibling2 -> sibling3 -> sibling4 -> null
+ | | | |
+ | | | null
+ | | |
+ | | child31 -> sibling32 -> null
+ | | | |
+ | | null null
+ | |
+ | child21 -> sibling22 -> sibling23 -> null
+ | | | |
+ | null null null
+ |
+ child11 -> sibling12 -> sibling13 -> sibling14 -> null
+ | | | |
+ | | | null
+ | | |
+ null null child131 -> null
+ |
+ null

Figure 1: Generic structure of un-flattened device tree

@@ -101,10 +108,10 @@ Figure 1: Generic structure of un-flattened device tree
Before executing OF unittest, it is required to attach the test data to
machine's device tree (if present). So, when selftest_data_add() is called,
at first it reads the flattened device tree data linked into the kernel image
-via the following kernel symbols:
+via the following kernel symbols::

-__dtb_testcases_begin - address marking the start of test data blob
-__dtb_testcases_end - address marking the end of test data blob
+ __dtb_testcases_begin - address marking the start of test data blob
+ __dtb_testcases_end - address marking the end of test data blob

Secondly, it calls of_fdt_unflatten_tree() to unflatten the flattened
blob. And finally, if the machine's device tree (i.e live tree) is present,
@@ -113,15 +120,15 @@ attaches itself as a live device tree.

attach_node_and_children() uses of_attach_node() to attach the nodes into the
live tree as explained below. To explain the same, the test data tree described
- in Figure 2 is attached to the live tree described in Figure 1.
+in Figure 2 is attached to the live tree described in Figure 1::

-root ('/')
- |
- testcase-data
- |
- test-child0 -> test-sibling1 -> test-sibling2 -> test-sibling3 -> null
- | | | |
- test-child01 null null null
+ root ('/')
+ |
+ testcase-data
+ |
+ test-child0 -> test-sibling1 -> test-sibling2 -> test-sibling3 -> null
+ | | | |
+ test-child01 null null null

Figure 2: Example test data tree to be attached to live tree.
@@ -134,39 +141,39 @@ In the function of_attach_node(), the new node is attached as the child of the
given parent in live tree. But, if parent already has a child then the new node
replaces the current child and turns it into its sibling. So, when the testcase
data node is attached to the live tree above (Figure 1), the final structure is
- as shown in Figure 3.
+as shown in Figure 3::

-root ('/')
- |
-testcase-data -> child1 -> sibling2 -> sibling3 -> sibling4 -> null
- | | | | |
- (...) | | | null
- | | child31 -> sibling32 -> null
- | | | |
- | | null null
- | |
- | child21 -> sibling22 -> sibling23 -> null
- | | | |
- | null null null
- |
- child11 -> sibling12 -> sibling13 -> sibling14 -> null
- | | | |
- null null | null
- |
- child131 -> null
- |
- null
------------------------------------------------------------------------
+ root ('/')
+ |
+ testcase-data -> child1 -> sibling2 -> sibling3 -> sibling4 -> null
+ | | | | |
+ (...) | | | null
+ | | child31 -> sibling32 -> null
+ | | | |
+ | | null null
+ | |
+ | child21 -> sibling22 -> sibling23 -> null
+ | | | |
+ | null null null
+ |
+ child11 -> sibling12 -> sibling13 -> sibling14 -> null
+ | | | |
+ null null | null
+ |
+ child131 -> null
+ |
+ null
+ -----------------------------------------------------------------------

-root ('/')
- |
-testcase-data -> child1 -> sibling2 -> sibling3 -> sibling4 -> null
- | | | | |
- | (...) (...) (...) null
- |
-test-sibling3 -> test-sibling2 -> test-sibling1 -> test-child0 -> null
- | | | |
- null null null test-child01
+ root ('/')
+ |
+ testcase-data -> child1 -> sibling2 -> sibling3 -> sibling4 -> null
+ | | | | |
+ | (...) (...) (...) null
+ |
+ test-sibling3 -> test-sibling2 -> test-sibling1 -> test-child0 -> null
+ | | | |
+ null null null test-child01

Figure 3: Live device tree structure after attaching the testcase-data.
@@ -176,7 +183,7 @@ Astute readers would have noticed that test-child0 node becomes the last
sibling compared to the earlier structure (Figure 2). After attaching first
test-child0 the test-sibling1 is attached that pushes the child node
(i.e. test-child0) to become a sibling and makes itself a child node,
- as mentioned above.
+as mentioned above.

If a duplicate node is found (i.e. if a node with same full_name property is
already present in the live tree), then the node isn't attached rather its
@@ -185,6 +192,7 @@ update_node_properties().

2.2. Removing the test data
+---------------------------

Once the test case execution is complete, selftest_data_remove is called in
order to remove the device nodes attached initially (first the leaf nodes are
--
2.21.1