summaryrefslogtreecommitdiffstats
path: root/dts/Bindings/writing-bindings.txt
blob: 27dfd2d8016e24eda4b305ce38db9f95adcc5264 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
DOs and DON'Ts for designing and writing Devicetree bindings

This is a list of common review feedback items focused on binding design. With
every rule, there are exceptions and bindings have many gray areas.

For guidelines related to patches, see
Documentation/devicetree/bindings/submitting-patches.txt


Overall design

- DO attempt to make bindings complete even if a driver doesn't support some
  features. For example, if a device has an interrupt, then include the
  'interrupts' property even if the driver is only polled mode.

- DON'T refer to Linux or "device driver" in bindings. Bindings should be
  based on what the hardware has, not what an OS and driver currently support.

- DO use node names matching the class of the device. Many standard names are
  defined in the DT Spec. If there isn't one, consider adding it.

- DO check that the example matches the documentation especially after making
  review changes.

- DON'T create nodes just for the sake of instantiating drivers. Multi-function
  devices only need child nodes when the child nodes have their own DT
  resources. A single node can be multiple providers (e.g. clocks and resets).

- DON'T use 'syscon' alone without a specific compatible string. A 'syscon'
  hardware block should have a compatible string unique enough to infer the
  register layout of the entire block (at a minimum).


Properties

- DO make 'compatible' properties specific. DON'T use wildcards in compatible
  strings. DO use fallback compatibles when devices are the same as or a subset
  of prior implementations. DO add new compatibles in case there are new
  features or bugs.

- DO use a vendor prefix on device specific property names. Consider if
  properties could be common among devices of the same class. Check other
  existing bindings for similar devices.

- DON'T redefine common properties. Just reference the definition and define
  constraints specific to the device.

- DO use common property unit suffixes for properties with scientific units.
  See property-units.txt.

- DO define properties in terms of constraints. How many entries? What are
  possible values? What is the order?


Board/SoC .dts Files

- DO put all MMIO devices under a bus node and not at the top-level.

- DO use non-empty 'ranges' to limit the size of child buses/devices. 64-bit
  platforms don't need all devices to have 64-bit address and size.