dt-bindings: nvmem: add U-Boot environment variables binding
Subsystems (2)
PATCH v2 1/1 dt-bindings: nvmem: add U-Boot environment variables binding
From: Rafał Miłecki <[email protected]>
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.
---
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
Documentation/devicetree/bindings/nvmem/u-boot,env.yaml new file +66 -0
@@ -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 <[email protected]> + +allOf: + - $ref: nvmem.yaml# + +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 + +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"; + }; + };
MAINTAINERS +5 -0
@@ -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 <[email protected]> +S: Maintained +F: Documentation/devicetree/bindings/nvmem/u-boot,env.yaml + UACCE ACCELERATOR FRAMEWORK M: Zhangfei Gao <[email protected]> M: Zhou Wang <[email protected]>
Signature · 1 line
2.34.1
Rob Herring
maintainerQuoted 5 lines · Rafał Miłecki
From: Rafał Miłecki <[email protected]>
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.
Quoted 49 lines
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 <[email protected]>---
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.yamlDocumentation/devicetree/bindings/nvmem/u-boot,env.yaml new file +21
-0@@ -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
Documentation/devicetree/bindings/nvmem/u-boot,env.yaml line 31
Quoted 10 lines
Documentation/devicetree/bindings/nvmem/u-boot,env.yaml new file +10
-0+ 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 <[email protected]> + +allOf: + - $ref: nvmem.yaml#
What exactly is used from nvmem.yaml? Based on the example, nothing.
Documentation/devicetree/bindings/nvmem/u-boot,env.yaml line 41
Quoted 11 lines
Documentation/devicetree/bindings/nvmem/u-boot,env.yaml new file +10
-0+ +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?
Quoted 45 lines
Documentation/devicetree/bindings/nvmem/u-boot,env.yaml new file +25
-0+ + 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"; + }; + };MAINTAINERS +5
-0@@ -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 <[email protected]> +S: Maintained +F: Documentation/devicetree/bindings/nvmem/u-boot,env.yaml + UACCE ACCELERATOR FRAMEWORK M: Zhangfei Gao <[email protected]> M: Zhou Wang <[email protected]>Signature · 1 line
2.34.1
Quoted 10 lines · Rob Herring
Quoted 5 lines · Rafał Miłecki
From: Rafał Miłecki <[email protected]>
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.
[bootloader]
Right now U-Boot doesn't use any binding for describing env variables. It's location is usually hardcoded, see (in U-Boot):
* CONFIG_ENV_ADDR
* CONFIG_ENV_SECT_SIZE
* CONFIG_ENV_ADDR_REDUND
[kernel]
There is no support for accessing U-Boot env data. This patch is the first step for adding such a support.
[user-space]
OpenWrt uses bash script to store a list of devices and their U-Boot env variables location. In a long term I'd like to replace it and use DT info + possibly a kernel exposed NVMEM data.
Quoted 53 lines
Quoted 53 lines
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 <[email protected]>---
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.yamlDocumentation/devicetree/bindings/nvmem/u-boot,env.yaml new file +25
-0@@ -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.
Quoted 8 lines
Documentation/devicetree/bindings/nvmem/u-boot,env.yaml line 31
Quoted 6 lines
Documentation/devicetree/bindings/nvmem/u-boot,env.yaml new file +6
-0+ +maintainers: + - Rafał Miłecki <[email protected]> + +allOf: + - $ref: nvmem.yaml#What exactly is used from
nvmem.yaml? Based on the example, nothing.
Nothing. I thought it's nice for a context. I'll drop it.
Quoted 7 lines
Quoted 6 lines
Documentation/devicetree/bindings/nvmem/u-boot,env.yaml new file +6
-0+ +properties: + compatible: + oneOf: + - description: A standalone env data block + const: u-boot,env
Quoted 6 lines
Documentation/devicetree/bindings/nvmem/u-boot,env.yaml line 41
Quoted 4 lines
Documentation/devicetree/bindings/nvmem/u-boot,env.yaml new file +4
-0+ - 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-countAren't these 2 discoverable based on a flag or count property?
U-Boot discovers that based on a type of flash device(s). In redundant mode env data can be stored on one or two flash devices.
U-Boot conditions:
/* Check flag scheme compatibility */
if (DEVTYPE(dev_current) == MTD_NORFLASH &&
DEVTYPE(!dev_current) == MTD_NORFLASH) {
environment.flag_scheme = FLAG_BOOLEAN;
} else if (DEVTYPE(dev_current) == MTD_NANDFLASH &&
DEVTYPE(!dev_current) == MTD_NANDFLASH) {
environment.flag_scheme = FLAG_INCREMENTAL;
} else if (DEVTYPE(dev_current) == MTD_DATAFLASH &&
DEVTYPE(!dev_current) == MTD_DATAFLASH) {
environment.flag_scheme = FLAG_BOOLEAN;
} else if (DEVTYPE(dev_current) == MTD_UBIVOLUME &&
DEVTYPE(!dev_current) == MTD_UBIVOLUME) {
environment.flag_scheme = FLAG_INCREMENTAL;
} else if (DEVTYPE(dev_current) == MTD_ABSENT &&
DEVTYPE(!dev_current) == MTD_ABSENT &&
IS_UBI(dev_current) == IS_UBI(!dev_current)) {
environment.flag_scheme = FLAG_INCREMENTAL;
} else {
fprintf(stderr, "Incompatible flash types!\n");
ret = -EINVAL;
goto open_cleanup;
}I thought it's better & more flexible to describe format explicitly in the DT. That way vendors have more options - they can e.g. start using incremental setup on NOR flash devices.
Quoted 45 lines
Quoted 45 lines
Documentation/devicetree/bindings/nvmem/u-boot,env.yaml new file +25
-0+ + 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"; + }; + };MAINTAINERS +5
-0@@ -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 <[email protected]> +S: Maintained +F: Documentation/devicetree/bindings/nvmem/u-boot,env.yaml + UACCE ACCELERATOR FRAMEWORK M: Zhangfei Gao <[email protected]> M: Zhou Wang <[email protected]>Signature · 1 line
2.34.1
Hei hei,
just want to give a little more background here from embedded non openwrt point of view. See below.
Am Mon, Feb 28, 2022 at 12:32:11PM +0100 schrieb Rafał Miłecki:
Quoted 12 lines · Rob Herring
Quoted 10 lines · Rafał Miłecki
Quoted 5 lines
From: Rafał Miłecki <[email protected]>
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.
Quoted 6 lines
[bootloader]
Right now U-Boot doesn't use any binding for describing env variables. It's location is usually hardcoded, see (in U-Boot):
*CONFIG_ENV_ADDR
*CONFIG_ENV_SECT_SIZE
*CONFIG_ENV_ADDR_REDUND
And more … U-Boot has a variety of options to store the U-Boot env, from the top of my head:
- at some offset in raw flash / mtd partition on NAND, NOR, serial dataflash, etc.
- at some offset on a block device, e.g. on eMMC
- as a file in a FAT partition
- in a UBI volume
- …
And yes, it's determined by some build option and hardcoded at compile time.
Quoted 8 lines
[kernel]
There is no support for accessing U-Boot env data. This patch is the first step for adding such a support.[user-space]
OpenWrt uses bash script to store a list of devices and their U-Boot env variables location. In a long term I'd like to replace it and use DT info + possibly a kernel exposed NVMEM data.
U-Boot source itself has userspace tools fw_setenv and fw_printenv and those look into /etc/fw_env.config on how that env should be accessed.
Greets
Alex
Quoted 159 lines
Quoted 55 lines
Quoted 55 lines
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 <[email protected]>---
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.yamlDocumentation/devicetree/bindings/nvmem/u-boot,env.yaml new file +25
-0@@ -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.Quoted 8 lines
Documentation/devicetree/bindings/nvmem/u-boot,env.yaml line 31
Quoted 6 lines
Documentation/devicetree/bindings/nvmem/u-boot,env.yaml new file +6
-0+ +maintainers: + - Rafał Miłecki <[email protected]> + +allOf: + - $ref: nvmem.yaml#What exactly is used from
nvmem.yaml? Based on the example, nothing.Nothing. I thought it's nice for a context. I'll drop it.
Quoted 7 lines
Quoted 6 lines
Documentation/devicetree/bindings/nvmem/u-boot,env.yaml new file +6
-0+ +properties: + compatible: + oneOf: + - description: A standalone env data block + const: u-boot,envQuoted 6 lines
Documentation/devicetree/bindings/nvmem/u-boot,env.yaml line 41
Quoted 4 lines
Documentation/devicetree/bindings/nvmem/u-boot,env.yaml new file +4
-0+ - 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-countAren't these 2 discoverable based on a flag or count property?
U-Boot discovers that based on a type of flash device(s). In redundant mode env data can be stored on one or two flash devices.
U-Boot conditions:
/* Check flag scheme compatibility */
if (DEVTYPE(dev_current)==MTD_NORFLASH&&DEVTYPE(!dev_current) == MTD_NORFLASH) { environment.flag_scheme = FLAG_BOOLEAN; } else if (DEVTYPE(dev_current) == MTD_NANDFLASH && DEVTYPE(!dev_current) == MTD_NANDFLASH) { environment.flag_scheme = FLAG_INCREMENTAL; } else if (DEVTYPE(dev_current) == MTD_DATAFLASH && DEVTYPE(!dev_current) == MTD_DATAFLASH) { environment.flag_scheme = FLAG_BOOLEAN; } else if (DEVTYPE(dev_current) == MTD_UBIVOLUME && DEVTYPE(!dev_current) == MTD_UBIVOLUME) { environment.flag_scheme = FLAG_INCREMENTAL; } else if (DEVTYPE(dev_current) == MTD_ABSENT && DEVTYPE(!dev_current) == MTD_ABSENT && IS_UBI(dev_current) == IS_UBI(!dev_current)) { environment.flag_scheme = FLAG_INCREMENTAL; } else { fprintf(stderr, "Incompatible flash types!\n"); ret = -EINVAL; goto open_cleanup; }I thought it's better & more flexible to describe format explicitly in the DT. That way vendors have more options - they can e.g. start using incremental setup on NOR flash devices.
Quoted 44 lines
Quoted 44 lines
Documentation/devicetree/bindings/nvmem/u-boot,env.yaml new file +25
-0+ + 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"; + }; + };MAINTAINERS +5
-0@@ -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 <[email protected]> +S: Maintained +F: Documentation/devicetree/bindings/nvmem/u-boot,env.yaml + UACCE ACCELERATOR FRAMEWORK M: Zhangfei Gao <[email protected]> M: Zhou Wang <[email protected]>Signature · 1 line
2.34.1
Quoted 41 lines · Alexander Dahl
Hei hei,
just want to give a little more background here from embedded non openwrt point of view. See below.
Am Mon, Feb 28, 2022 at 12:32:11PM +0100 schrieb Rafał Miłecki:
Quoted 12 lines · Rob Herring
Quoted 10 lines · Rafał Miłecki
Quoted 5 lines
From: Rafał Miłecki <[email protected]>
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.
Quoted 6 lines
[bootloader]
Right now U-Boot doesn't use any binding for describing env variables. It's location is usually hardcoded, see (in U-Boot):
*CONFIG_ENV_ADDR
*CONFIG_ENV_SECT_SIZE
*CONFIG_ENV_ADDR_REDUNDAnd more … U-Boot has a variety of options to store the U-Boot env, from the top of my head:
- at some offset in raw flash / mtd partition on NAND, NOR, serial dataflash, etc.
- at some offset on a block device, e.g. on eMMC
- as a file in a FAT partition
- in a UBI volume
- …And yes, it's determined by some build option and hardcoded at compile time.
Quoted 4 lines
[kernel]
There is no support for accessing U-Boot env data. This patch is the first step for adding such a support.
Quoted 8 lines
Quoted 4 lines
[user-space]
OpenWrt uses bash script to store a list of devices and their U-Boot env variables location. In a long term I'd like to replace it and use DT info + possibly a kernel exposed NVMEM data.U-Boot source itself has userspace tools
fw_setenvandfw_printenvand those look into/etc/fw_env.configon how that env should be accessed.
I wasn't 100% clear on that but OpenWrt actually uses those U-Boot tools
OpenWrt scripts I mentioned can be found there:
https://git.openwrt.org/?p=openwrt/openwrt.git;a=tree;f=package/boot/uboot-envtools/files;h=687c89806f72756053457a7ab7245bff1c4dcfe8;hb=HEAD
Random example:
linksys,wrt1900ac-v1)
ubootenv_add_uci_config "/dev/mtd1" "0x0" "0x40000" "0x20000" ;; linksys,wrt3200acm|\ linksys,wrt32x) ubootenv_add_uci_config "/dev/mtd1" "0x0" "0x20000" "0x20000" ;;
So those scripts simply generate /etc/fw_env.config required by fw_printenv / fw_setenv. They have to match what's used by U-Boot at compilation time.
My long term plan is to move that info to DTS and share it across projects.