[PATCH v2 00/20] nvmem: core: introduce NVMEM layouts

Michael Walle
2022-09-01T22:21:20Z

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@walle.cc/

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.

Therefore, introduce NVMEM layouts. They operate on the NVMEM device and
can add cells during runtime. That way it is possible to add more 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).

The imx-ocotp driver is the only user of the global post processing hook,
convert it to nvmem layouts and drop the global post pocessing hook. Please
note, that this change is only compile-time tested.

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. These two patches
are not expected to be applied, but rather to show another example of
how to use the layouts.

For now, the layouts are selected by a specific 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 (20):
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: move struct nvmem_cell_info to nvmem-provider.h
nvmem: core: drop the removal of the cells in nvmem_add_cells()
nvmem: core: add nvmem_add_one_cell()
nvmem: core: use nvmem_add_one_cell() in nvmem_add_cells_from_of()
nvmem: core: introduce NVMEM layouts
nvmem: core: add per-cell post processing
nvmem: core: allow to modify a cell before adding it
nvmem: imx-ocotp: replace global post processing with layouts
nvmem: cell: drop global cell_post_process
nvmem: core: drop priv pointer in post process callback
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
arm64: dts: ls1028a: sl28: get MAC addresses from VPD
RFC nvmem: layouts: rewrite the u-boot-env driver as a NVMEM layout
RFC nvmem: layouts: u-boot-env: add device node

.../devicetree/bindings/mtd/mtd.yaml | 7 +-
.../nvmem/layouts/kontron,sl28-vpd.yaml | 67 +++++
Documentation/driver-api/nvmem.rst | 15 ++
.../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 | 4 +
drivers/nvmem/Makefile | 1 +
drivers/nvmem/core.c | 251 +++++++++++++-----
drivers/nvmem/imx-ocotp.c | 32 ++-
drivers/nvmem/layouts/Kconfig | 22 ++
drivers/nvmem/layouts/Makefile | 7 +
drivers/nvmem/layouts/sl28vpd.c | 144 ++++++++++
drivers/nvmem/layouts/u-boot-env.c | 146 ++++++++++
drivers/nvmem/u-boot-env.c | 218 ---------------
include/linux/etherdevice.h | 14 +
include/linux/nvmem-consumer.h | 16 +-
include/linux/nvmem-provider.h | 90 ++++++-
include/linux/of.h | 25 ++
21 files changed, 775 insertions(+), 313 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

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2.30.2