mtd: ubi: behave like a good MTD citizen

As of now one can easily trigger the existence of "ghost" UBI devices or even worse by removing e.g. the SPI bus driver which previously provided access to an SPI-NAND chip.

Make UBI behave more like other MTD users and create/remove UBI devices based on MTD notifications. As removing could previously fail in case of an ubiblock device still being in use, make sure there are no excuses preventing release of an already gone MTD partition.

This makes it possible to attach UBI devices immediately after the MTD partition becomes available, which will allow using UBI volumes as nvmem-cells provider in the future [1]. Introduce new device tree compatible "linux,ubi" to be used on MTD partitions which should be attached.

In order to make sure ubiblock devices are still created according to the module or kernel parameters, let ubiblock creation from parameters be triggered by UBI_VOLUME_ADDED notifications instead of trying only once during boot.

[1]: https://forum.openwrt.org/t/asus-tuf-ax4200-support/155738/44?u=daniel

Daniel Golle (4):
mtd: ubi: block: don't return on error when removing
mtd: ubi: block: use notifier to create ubiblock from parameter
dt-bindings: mtd: partitions: add linux,ubi
mtd: ubi: attach MTD partition from device-tree

 .../bindings/mtd/partitions/ubi.yaml          |  49 +++++
 drivers/mtd/ubi/block.c                       | 158 ++++++++-------
 drivers/mtd/ubi/build.c                       | 189 ++++++++++++------
 drivers/mtd/ubi/cdev.c                        |   4 +-
 drivers/mtd/ubi/ubi.h                         |   6 +-
 5 files changed, 271 insertions(+), 135 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/mtd/partitions/ubi.yaml

base-commit: b5fda08ef213352ac2df7447611eb4d383cce929

2.40.1