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61 lines
2.3 KiB
Plaintext
61 lines
2.3 KiB
Plaintext
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DOs and DON'Ts for designing and writing Devicetree bindings
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This is a list of common review feedback items focused on binding design. With
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every rule, there are exceptions and bindings have many gray areas.
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For guidelines related to patches, see
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Documentation/devicetree/bindings/submitting-patches.txt
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Overall design
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- DO attempt to make bindings complete even if a driver doesn't support some
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features. For example, if a device has an interrupt, then include the
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'interrupts' property even if the driver is only polled mode.
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- DON'T refer to Linux or "device driver" in bindings. Bindings should be
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based on what the hardware has, not what an OS and driver currently support.
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- DO use node names matching the class of the device. Many standard names are
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defined in the DT Spec. If there isn't one, consider adding it.
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- DO check that the example matches the documentation especially after making
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review changes.
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- DON'T create nodes just for the sake of instantiating drivers. Multi-function
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devices only need child nodes when the child nodes have their own DT
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resources. A single node can be multiple providers (e.g. clocks and resets).
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- DON'T use 'syscon' alone without a specific compatible string. A 'syscon'
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hardware block should have a compatible string unique enough to infer the
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register layout of the entire block (at a minimum).
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Properties
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- DO make 'compatible' properties specific. DON'T use wildcards in compatible
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strings. DO use fallback compatibles when devices are the same as or a subset
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of prior implementations. DO add new compatibles in case there are new
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features or bugs.
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- DO use a vendor prefix on device specific property names. Consider if
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properties could be common among devices of the same class. Check other
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existing bindings for similar devices.
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- DON'T redefine common properties. Just reference the definition and define
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constraints specific to the device.
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- DO use common property unit suffixes for properties with scientific units.
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See property-units.txt.
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- DO define properties in terms of constraints. How many entries? What are
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possible values? What is the order?
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Board/SoC .dts Files
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- DO put all MMIO devices under a bus node and not at the top-level.
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- DO use non-empty 'ranges' to limit the size of child buses/devices. 64-bit
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platforms don't need all devices to have 64-bit address and size.
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