On Thu, Feb 17, 2022 at 02:02:35PM +0100, Rafał Miłecki wrote: > From: Rafał Miłecki <rafal@xxxxxxxxxx> > > U-Boot uses environment variables for storing device setup data. It > usually needs to be accessed by a bootloader, kernel and often > user-space. How much of this is already in use vs. proposed? I know I've seen something, but that may have been a u-boot env string in 'label' and that's it. > This binding allows describing environment data located in a raw flash > partition. It's treated as NVMEM device and can be reused later for > other storage devices. > > Using DT should be cleaner than hardcoding & duplicating such info in > multiple places. Bootloader & kernel can share DTS and user-space can > try reading it too or just have correct data exposed by a kernel. > > A custom "compatible" string allows system to automatically load > relevant NVMEM driver but phandle can be also used for reading raw > location. > > Signed-off-by: Rafał Miłecki <rafal@xxxxxxxxxx> > --- > V2: Update descriptions to don't make this binding MTD (flash partition) > specific. Mention multiple possible storage ways. > --- > .../devicetree/bindings/nvmem/u-boot,env.yaml | 66 +++++++++++++++++++ > MAINTAINERS | 5 ++ > 2 files changed, 71 insertions(+) > create mode 100644 Documentation/devicetree/bindings/nvmem/u-boot,env.yaml > > diff --git a/Documentation/devicetree/bindings/nvmem/u-boot,env.yaml b/Documentation/devicetree/bindings/nvmem/u-boot,env.yaml > new file mode 100644 > index 000000000000..a53e34152c97 > --- /dev/null > +++ b/Documentation/devicetree/bindings/nvmem/u-boot,env.yaml > @@ -0,0 +1,66 @@ > +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause > +%YAML 1.2 > +--- > +$id: http://devicetree.org/schemas/nvmem/u-boot,env.yaml# > +$schema: http://devicetree.org/meta-schemas/core.yaml# > + > +title: U-Boot environment variables > + > +description: | > + U-Boot uses environment variables to store device parameters and > + configuration. They may be used for booting process, setup or keeping end user > + info. > + > + Data is stored using U-Boot specific formats (variant specific header and NUL > + separated key-value pairs). > + > + Environment data can be stored on various storage entities, e.g.: > + 1. Raw flash partition > + 2. UBI volume > + > + This binding allows marking storage device (as containing env data) and > + specifying used format. > + > + Right now only flash partition case is covered but it may be extended to e.g. > + UBI volumes in the future. > + > +maintainers: > + - Rafał Miłecki <rafal@xxxxxxxxxx> > + > +allOf: > + - $ref: nvmem.yaml# What exactly is used from nvmem.yaml? Based on the example, nothing. > + > +properties: > + compatible: > + oneOf: > + - description: A standalone env data block > + const: u-boot,env > + - description: Two redundant blocks with active one flagged > + const: u-boot,env-redundant-bool > + - description: Two redundant blocks with active having higher counter > + const: u-boot,env-redundant-count Aren't these 2 discoverable based on a flag or count property? > + > + reg: > + maxItems: 1 > + > +unevaluatedProperties: false > + > +examples: > + - | > + partitions { > + compatible = "fixed-partitions"; > + #address-cells = <1>; > + #size-cells = <1>; > + > + partition@0 { > + reg = <0x0 0x40000>; > + label = "u-boot"; > + read-only; > + }; > + > + env: partition@40000 { > + compatible = "u-boot,env"; > + reg = <0x40000 0x10000>; > + label = "u-boot-env"; > + }; > + }; > diff --git a/MAINTAINERS b/MAINTAINERS > index 66aa3a589f6a..55c56ce82856 100644 > --- a/MAINTAINERS > +++ b/MAINTAINERS > @@ -19905,6 +19905,11 @@ W: http://linuxtv.org > T: git git://linuxtv.org/media_tree.git > F: drivers/media/pci/tw686x/ > > +U-BOOT ENVIRONMENT VARIABLES > +M: Rafał Miłecki <rafal@xxxxxxxxxx> > +S: Maintained > +F: Documentation/devicetree/bindings/nvmem/u-boot,env.yaml > + > UACCE ACCELERATOR FRAMEWORK > M: Zhangfei Gao <zhangfei.gao@xxxxxxxxxx> > M: Zhou Wang <wangzhou1@xxxxxxxxxxxxx> > -- > 2.34.1 > >
