[PATCH V2] dt-bindings: nvmem: add U-Boot environment variables binding
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. --- .../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@milecki.pl + +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"; + }; + }; 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@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
On Thu, Feb 17, 2022 at 02:02:35PM +0100, 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.
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@milecki.pl
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.:
- Raw flash partition
- 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
+allOf:
- $ref: nvmem.yaml#
What exactly is used from nvmem.yaml? Based on the example, nothing.
+properties:
- compatible:
- oneOf:
- description: A standalone env data blockconst: u-boot,env
- description: Two redundant blocks with active one flaggedconst: u-boot,env-redundant-bool- description: Two redundant blocks with active having higher counterconst: 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@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 -- 2.34.1
On 25.02.2022 17:42, Rob Herring wrote:
On Thu, Feb 17, 2022 at 02:02:35PM +0100, 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.
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.
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.
.../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.:
- Raw flash partition
- 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
+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.
+properties:
- compatible:
- oneOf:
- description: A standalone env data blockconst: u-boot,env
- description: Two redundant blocks with active one flaggedconst: u-boot,env-redundant-bool- description: Two redundant blocks with active having higher counterconst: 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.
- 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@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
-- 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:
On 25.02.2022 17:42, Rob Herring wrote:
On Thu, Feb 17, 2022 at 02:02:35PM +0100, 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.
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
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.
[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
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.
.../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.:
- Raw flash partition
- 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
+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.
+properties:
- compatible:
- oneOf:
- description: A standalone env data blockconst: u-boot,env
- description: Two redundant blocks with active one flaggedconst: u-boot,env-redundant-bool- description: Two redundant blocks with active having higher counterconst: 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.
- 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@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
-- 2.34.1
On 7.03.2022 11:24, Alexander Dahl wrote:
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:
On 25.02.2022 17:42, Rob Herring wrote:
On Thu, Feb 17, 2022 at 02:02:35PM +0100, 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.
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
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.
[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.
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-e...
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.
participants (3)
-
Alexander Dahl -
Rafał Miłecki -
Rob Herring