On 10.03.2022 09:45, Michal Simek wrote:
On 3/9/22 16:40, Rob Herring wrote:
On Wed, Mar 09, 2022 at 02:42:43PM +0100, Michal Simek wrote:
On 2/28/22 14:12, Rafał Miłecki wrote:
From: Rafał Miłecki rafal@milecki.pl
U-Boot uses environment variables for storing device setup data. It usually needs to be accessed by a bootloader, kernel and often user-space.
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@milecki.pl
V2: Update descriptions to don't make this binding MTD (flash partition) specific. Mention multiple possible storage ways. V3: Drop allOf: - $ref: nvmem.yaml# as we don't use anything rom the nvmem.yaml. Thanks Rob.
.../devicetree/bindings/nvmem/u-boot,env.yaml | 62 +++++++++++++++++++ MAINTAINERS | 5 ++ 2 files changed, 67 insertions(+) create mode 100644 Documentation/devicetree/bindings/nvmem/u-boot,env.yaml
diff --git a/Documentation/devicetree/bindings/nvmem/u-boot,env.yaml b/Documentation/devicetree/bindings/nvmem/u-boot,env.yaml new file mode 100644 index 000000000000..e70b2a60cb9a --- /dev/null +++ b/Documentation/devicetree/bindings/nvmem/u-boot,env.yaml @@ -0,0 +1,62 @@ +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause +%YAML 1.2 +--- +$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@milecki.pl
+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
+ reg: + maxItems: 1
+additionalProperties: 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>; + }; + }; diff --git a/MAINTAINERS b/MAINTAINERS index db8052bc1d26..24fc181a7e6c 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -19958,6 +19958,11 @@ 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@milecki.pl +S: Maintained +F: Documentation/devicetree/bindings/nvmem/u-boot,env.yaml
UACCE ACCELERATOR FRAMEWORK M: Zhangfei Gao zhangfei.gao@linaro.org M: Zhou Wang wangzhou1@hisilicon.com
I think that parsing these partitions is quite sw intensive process and I can't still see the value to have compatible string here.
It's always good to know what a node represents.
Also agree but isn't it enough to use proper label for it?
Let me quote Rob here:
'label' is supposed to correspond to a sticker on a port or something human identifiable
^^ https://patchwork.ozlabs.org/comment/2812214/
"label" is already abused for naming MTD partitions, I don't think it's a good idea to abuse it even more for different purposes. Also "compatible" is a standard way for describing hardware blocks & various entities (identifying them).
I'm also wondering if using "label" instead of "compatible" wouldn't require breaking changes in some DT files. What if someone uses a random "label" (e.g. "ub00tenv") and has user-space based on that MTD partition name? If we require changing "label" that will require people to also update names in other places (user-space). I'm not sure how valid is that argument, just wondering.