On Sat, 20 Jan 2024 16:50:48 +0530, Amrit Anand wrote: > From: Elliot Berman <quic_eberman@xxxxxxxxxxx> > > Device manufacturers frequently ship multiple boards or SKUs under a > single software package. These software packages will ship multiple > devicetree blobs and require some mechanism to pick the correct DTB for > the board the software package was deployed. Introduce a common > definition for adding board identifiers to device trees. board-id > provides a mechanism for bootloaders to select the appropriate DTB which > is vendor/OEM-agnostic. > > Isn't that what the compatible property is for? > ----------------------------------------------- > The compatible property can be used for board matching, but requires > bootloaders and/or firmware to maintain a database of possible strings > to match against or have complex compatible string matching. Compatible > string matching becomes complicated when there are multiple versions of > board: the device tree selector should recognize a DTB that cares to > distinguish between v1/v2 and a DTB that doesn't make the distinction. > An eeprom either needs to store the compatible strings that could match > against the board or the bootloader needs to have vendor-specific > decoding logic for the compatible string. Neither increasing eeprom > storage nor adding vendor-specific decoding logic is desirable. > > The solution proposed here is simpler to implement and doesn't require > updating firmware or bootloader for every new board. > > How is this better than Qualcomm's qcom,msm-id/qcom,board-id? > ------------------------------------------------------------- > The selection process for devicetrees was Qualcomm-specific and not > useful for other devices and bootloaders that were not developed by > Qualcomm because a complex algorithm was used to implement. Board-ids > provide a matching solution that can be implemented by bootloaders > without introducing vendor-specific code. Qualcomm uses three > devicetree properties: msm-id (interchangeably: soc-id), board-id, and > pmic-id. This does not scale well for use casese which use identifiers, > for example, to distinguish between a display panel. For a display > panel, an approach could be to add a new property: display-id, > but now bootloaders need to be updated to also read this property. We > want to avoid requiring to update bootloaders with new hardware > identifiers: a bootloader need only recognize the identifiers it can > handle. > > Signed-off-by: Elliot Berman <quic_eberman@xxxxxxxxxxx> > Signed-off-by: Amrit Anand <quic_amrianan@xxxxxxxxxxx> > --- > .../devicetree/bindings/hwinfo/board-id.yaml | 53 ++++++++++++++++++++++ > 1 file changed, 53 insertions(+) > create mode 100644 Documentation/devicetree/bindings/hwinfo/board-id.yaml > My bot found errors running 'make DT_CHECKER_FLAGS=-m dt_binding_check' on your patch (DT_CHECKER_FLAGS is new in v5.13): yamllint warnings/errors: ./Documentation/devicetree/bindings/hwinfo/board-id.yaml:23:11: [error] string value is redundantly quoted with any quotes (quoted-strings) ./Documentation/devicetree/bindings/hwinfo/board-id.yaml:25:11: [error] string value is redundantly quoted with any quotes (quoted-strings) dtschema/dtc warnings/errors: doc reference errors (make refcheckdocs): See https://patchwork.ozlabs.org/project/devicetree-bindings/patch/1705749649-4708-2-git-send-email-quic_amrianan@xxxxxxxxxxx The base for the series is generally the latest rc1. A different dependency should be noted in *this* patch. If you already ran 'make dt_binding_check' and didn't see the above error(s), then make sure 'yamllint' is installed and dt-schema is up to date: pip3 install dtschema --upgrade Please check and re-submit after running the above command yourself. Note that DT_SCHEMA_FILES can be set to your schema file to speed up checking your schema. However, it must be unset to test all examples with your schema.
