On Tue, May 17, 2022 at 01:58:41PM -0500, Rob Herring wrote: > On Thu, May 12, 2022 at 02:17:48AM +0300, Serge Semin wrote: > > It's redundant to have the 'dma-coherent' property explicitly specified in > > the DT schema because it's a generic property described in the core > > DT-schema by which the property is always evaluated. > > It is not redundant. > > The core schema defines the property (as a boolean), but this schema > defines it being used in this binding. Otherwise, it won't be allowed. I thought that the generic properties like ranges, dma-ranges, etc including the dma-coherent one due to being defined in the dt-core schema are always evaluated. As such seeing the unevaluatedProperties property is set to false here, they can be used in the DT-nodes with no need to be explicitly specified in the DT node bindings. In addition to that I tested this assumption by dropping the dma-coherent property definition from the AHCI-common schema and executed the DT-bindings check procedure. No error has been spotted: > [fancer@mobilestation] kernel $ cat Documentation/devicetree/bindings/ata/snps,dwc-ahci.yaml | grep dma-coherent > dma-coherent; > [fancer@mobilestation] kernel $ make -j8 DT_SCHEMA_FILES=Documentation/devicetree/bindings/ata/snps,dwc-ahci.yaml dt_binding_check > LINT Documentation/devicetree/bindings > DTEX Documentation/devicetree/bindings/ata/snps,dwc-ahci.example.dts > CHKDT Documentation/devicetree/bindings/processed-schema.json > SCHEMA Documentation/devicetree/bindings/processed-schema.json > DTC Documentation/devicetree/bindings/ata/snps,dwc-ahci.example.dtb > CHECK Documentation/devicetree/bindings/ata/snps,dwc-ahci.example.dtb > [fancer@mobilestation] kernel $ cat Documentation/devicetree/bindings/ata/snps,dwc-ahci.example.dts | grep dma-coherent > dma-coherent; > [fancer@mobilestation] kernel $ echo $? > 0 Due to that here are a few backward questions: 1) Am I doing something wrong in the framework of the DT-bindings evaluation? Really I even tried to specify unknown property in the DT-bindings example like "bla-bla-bla;" and no evaluation error was printed. Anyway If what you are saying was correct I would have got an error during the DT-bindings evaluation, but as you can see there was none. 2) Am I wrong in thinking that the unevaluatedProperties setting concerns the generic properties defined in the DT-core schema? If it doesn't concern the generic properties then does it work for the $ref'ed schemas only? Getting back to the patch topic. We need to drop the dma-coherent property from the schema anyway. AHCI-specification doesn't regulate the DMA operations coherency. The dma-coherent property is more specific to the particular controller implementation mainly dependent on the platform settings. So I'll change the patch log, but get to keep the patch in the series. What do you think? -Sergey > > Rob
