On 25.08.2022 23:44, Michael Walle wrote:
This is now the third attempt to fetch the MAC addresses from the VPD for the Kontron sl28 boards. Previous discussions can be found here: https://lore.kernel.org/lkml/20211228142549.1275412-1-michael@xxxxxxxx/ NVMEM cells are typically added by board code or by the devicetree. But as the cells get more complex, there is (valid) push back from the devicetree maintainers to not put that handling in the devicetree.
I dropped the ball waiting for Rob's reponse in the [PATCH 0/2] dt-bindings: nvmem: support describing cells https://lore.kernel.org/linux-arm-kernel/0b7b8f7ea6569f79524aea1a3d783665@xxxxxxxx/T/ Before we go any further can we have a clear answer from Rob (or Krzysztof now too?): Is there any point in having bindings like: compatible = "mac-address"; for NVMEM cells nodes? So systems (Linux, U-Boot) can handle them in a more generic way? Or do we prefer more conditional drivers code (or layouts code as in this Michael's proposal) that will handle cells properly based on their names? I'm not arguing for any solution. I just want to make sure we choose the right way to proceed.
Therefore, introduce NVMEM layouts. They operate on the NVMEM device and can add cells during runtime. That way it is possible to add complex cells than it is possible right now with the offset/length/bits description in the device tree. For example, you can have post processing for individual cells (think of endian swapping, or ethernet offset handling). You can also have cells which have no static offset, like the ones in an u-boot environment. The last patches will convert the current u-boot environment driver to a NVMEM layout and lifting the restriction that it only works with mtd devices. But as it will change the required compatible strings, it is marked as RFC for now. It also needs to have its device tree schema update which is left out here.
So do I get it right that we want to have: 1. NVMEM drivers for providing I/O access to NVMEM devices 2. NVMEM layouts for parsing & NVMEM cells and translating their content ? I guess it sounds good and seems to be a clean solution. One thing I believe you need to handle is replacing "cell_post_process" callback with your layout thing. I find it confusing to have 1. cell_post_process() CB at NVMEM device level 2. post_process() CB at NVMEM cell level
For now, the layouts are selected by a specifc compatible string in a device tree. E.g. the VPD on the kontron sl28 do (within a SPI flash node): compatible = "kontron,sl28-vpd", "user-otp"; or if you'd use the u-boot environment (within an MTD patition): compatible = "u-boot,env", "nvmem"; The "user-otp" (or "nvmem") will lead to a NVMEM device, the "kontron,sl28-vpd" (or "u-boot,env") will then apply the specific layout on top of the NVMEM device. NVMEM layouts as modules? While possible in principle, it doesn't make any sense because the NVMEM core can't be compiled as a module. The layouts needs to be available at probe time. (That is also the reason why they get registered with subsys_initcall().) So if the NVMEM core would be a module, the layouts could be modules, too. Michael Walle (14): net: add helper eth_addr_add() of: base: add of_parse_phandle_with_optional_args() nvmem: core: add an index parameter to the cell nvmem: core: drop the removal of the cells in nvmem_add_cells() nvmem: core: add nvmem_add_one_cell() nvmem: core: introduce NVMEM layouts nvmem: core: add per-cell post processing dt-bindings: mtd: relax the nvmem compatible string dt-bindings: nvmem: add YAML schema for the sl28 vpd layout nvmem: layouts: add sl28vpd layout nvmem: core: export nvmem device size nvmem: layouts: rewrite the u-boot-env driver as a NVMEM layout nvmem: layouts: u-boot-env: add device node arm64: dts: ls1028a: sl28: get MAC addresses from VPD .../devicetree/bindings/mtd/mtd.yaml | 7 +- .../nvmem/layouts/kontron,sl28-vpd.yaml | 52 +++++ .../fsl-ls1028a-kontron-kbox-a-230-ls.dts | 8 + .../fsl-ls1028a-kontron-sl28-var1.dts | 2 + .../fsl-ls1028a-kontron-sl28-var2.dts | 4 + .../fsl-ls1028a-kontron-sl28-var4.dts | 2 + .../freescale/fsl-ls1028a-kontron-sl28.dts | 13 ++ drivers/nvmem/Kconfig | 2 + drivers/nvmem/Makefile | 1 + drivers/nvmem/core.c | 183 +++++++++++---- drivers/nvmem/imx-ocotp.c | 4 +- drivers/nvmem/layouts/Kconfig | 22 ++ drivers/nvmem/layouts/Makefile | 7 + drivers/nvmem/layouts/sl28vpd.c | 144 ++++++++++++ drivers/nvmem/layouts/u-boot-env.c | 147 ++++++++++++ drivers/nvmem/u-boot-env.c | 218 ------------------ include/linux/etherdevice.h | 14 ++ include/linux/nvmem-consumer.h | 11 + include/linux/nvmem-provider.h | 47 +++- include/linux/of.h | 25 ++ 20 files changed, 649 insertions(+), 264 deletions(-) create mode 100644 Documentation/devicetree/bindings/nvmem/layouts/kontron,sl28-vpd.yaml create mode 100644 drivers/nvmem/layouts/Kconfig create mode 100644 drivers/nvmem/layouts/Makefile create mode 100644 drivers/nvmem/layouts/sl28vpd.c create mode 100644 drivers/nvmem/layouts/u-boot-env.c delete mode 100644 drivers/nvmem/u-boot-env.c
