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.
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.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 <[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";
+ };
+ };
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 <[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]>
--
2.34.1
On Thu, Feb 17, 2022 at 02:02:35PM +0100, Rafał Miłecki wrote:
> 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.
> 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.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 <[email protected]>
> +
> +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 <[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]>
> --
> 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 <[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.
>> 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.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 <[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.
>> +
>> +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?
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 <[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]>
>> --
>> 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 <[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
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 <[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.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 <[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.
>
>
> > > +
> > > +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?
>
> 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 <[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]>
> > > --
> > > 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 <[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
>
> 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-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.