1 .. SPDX-License-Identifier: GPL-2.0
2
3 =====================================
4 Devicetree Sources (DTS) Coding Style
5 =====================================
6
7 When writing Devicetree Sources (DTS) please o
8 should be considered complementary to any rule
9 the Devicetree Specification and the dtc compi
10 builds).
11
12 Individual architectures and subarchitectures
13 making the coding style stricter.
14
15 Naming and Valid Characters
16 ---------------------------
17
18 The Devicetree Specification allows a broad ra
19 and property names, but this coding style narr
20 better code readability.
21
22 1. Node and property names can use only the fo
23
24 * Lowercase characters: [a-z]
25 * Digits: [0-9]
26 * Dash: -
27
28 2. Labels can use only the following character
29
30 * Lowercase characters: [a-z]
31 * Digits: [0-9]
32 * Underscore: _
33
34 3. Unless a bus defines differently, unit addr
35 hexadecimal digits, without leading zeros (
36
37 4. Hex values in properties, e.g. "reg", shall
38 part can be padded with leading zeros.
39
40 Example::
41
42 gpi_dma2: dma-controller@a00000 {
43 compatible = "qcom,sm8550-gpi-
44 reg = <0x0 0x00a00000 0x0 0x60
45 }
46
47 Order of Nodes
48 --------------
49
50 1. Nodes on any bus, thus using unit addresses
51 ordered by unit address in ascending order.
52 Alternatively for some subarchitectures, no
53 grouped together, e.g. all I2C controllers
54 breaks unit address ordering.
55
56 2. Nodes without unit addresses shall be order
57 name. For a few node types, they can be or
58 pin configuration states ordered by value o
59
60 3. When extending nodes in the board DTS via &
61 ordered either alpha-numerically or by keep
62 the choice depends on the subarchitecture.
63
64 The above-described ordering rules are easy to
65 chances of conflicts for simultaneous addition
66 in navigating through the DTS source.
67
68 Example::
69
70 /* SoC DTSI */
71
72 / {
73 cpus {
74 /* ... */
75 };
76
77 psci {
78 /* ... */
79 };
80
81 soc@0 {
82 dma: dma-controller@10
83 /* ... */
84 };
85
86 clk: clock-controller@
87 /* ... */
88 };
89 };
90 };
91
92 /* Board DTS - alphabetical order */
93
94 &clk {
95 /* ... */
96 };
97
98 &dma {
99 /* ... */
100 };
101
102 /* Board DTS - alternative order, keep
103
104 &dma {
105 /* ... */
106 };
107
108 &clk {
109 /* ... */
110 };
111
112 Order of Properties in Device Node
113 ----------------------------------
114
115 The following order of properties in device no
116
117 1. "compatible"
118 2. "reg"
119 3. "ranges"
120 4. Standard/common properties (defined by comm
121 vendor-prefixes)
122 5. Vendor-specific properties
123 6. "status" (if applicable)
124 7. Child nodes, where each node is preceded wi
125
126 The "status" property is by default "okay", th
127
128 The above-described ordering follows this appr
129
130 1. Most important properties start the node: c
131 match unit address.
132 2. Each node will have common properties in si
133 3. Status is the last information to annotate
134 finished (board resources are needed).
135
136 Example::
137
138 /* SoC DTSI */
139
140 device_node: device-class@6789abc {
141 compatible = "vendor,device";
142 reg = <0x0 0x06789abc 0x0 0xa1
143 ranges = <0x0 0x0 0x06789abc 0
144 #dma-cells = <1>;
145 clocks = <&clock_controller 0>
146 clock-names = "bus", "host";
147 #address-cells = <1>;
148 #size-cells = <1>;
149 vendor,custom-property = <2>;
150 status = "disabled";
151
152 child_node: child-class@100 {
153 reg = <0x100 0x200>;
154 /* ... */
155 };
156 };
157
158 /* Board DTS */
159
160 &device_node {
161 vdd-supply = <&board_vreg1>;
162 status = "okay";
163 }
164
165 Indentation
166 -----------
167
168 1. Use indentation according to Documentation/
169 2. Each entry in arrays with multiple cells, e
170 shall be enclosed in <>.
171 3. For arrays spanning across lines, it is pre
172 entries with opening < from the first line.
173
174 Example::
175
176 thermal-sensor@c271000 {
177 compatible = "qcom,sm8550-tsen
178 reg = <0x0 0x0c271000 0x0 0x10
179 <0x0 0x0c222000 0x0 0x10
180 };
181
182 Organizing DTSI and DTS
183 -----------------------
184
185 The DTSI and DTS files shall be organized in a
186 reusable parts of hardware. Typically, this m
187 into several files:
188
189 1. DTSI with contents of the entire SoC, witho
190 on the SoC.
191 2. If applicable: DTSI with common or re-usabl
192 entire System-on-Module.
193 3. DTS representing the board.
194
195 Hardware components that are present on the bo
196 board DTS, not in the SoC or SoM DTSI. A part
197 external reference SoC input clock, which coul
198 the SoC DTSI with its frequency provided by ea
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