Re: [PATCH V3 1/6] dt-bindings: nvmem: layouts: add U-Boot environment variables layout
Hi Rob,
r...@kernel.org wrote on Mon, 15 Jan 2024 11:09:03 -0600:
> On Thu, Jan 04, 2024 at 10:10:13AM +0100, Rafał Miłecki wrote:
> > On 4.01.2024 08:58, Miquel Raynal wrote:
> > > r...@kernel.org wrote on Wed, 3 Jan 2024 17:11:29 -0700:
> > > > On Thu, Dec 21, 2023 at 06:34:16PM +0100, Rafał Miłecki wrote:
> > > > > From: Rafał Miłecki
> > > > >
> > > > > U-Boot env data is a way of storing firmware variables. It's a format
> > > > > that can be used of top of various storage devices. Its binding should
> > > > > be an NVMEM layout instead of a standalone device.
> > > > >
> > > > > This patch adds layout binding which allows using it on top of MTD
> > > > > NVMEM
> > > > > device as well as any other. At the same time it deprecates the old
> > > > > combined binding.
> > > >
> > > > I don't understand the issue. From a DT perspective, there isn't. A
> > > > partition is not a device, but is describing the layout of storage
> > > > already.
> > >
> > > Actually I think what Rafał wants to do goes in the right direction but
> > > I also understand from a binding perspective it may be a little
> > > confusing, even more if we consider "NVMEM" a Linux specific concept.
> > >
> > > There is today a "u-boot env" NVMEM *device* description which
> > > almost sits at the same level as eg. an eeprom device. We cannot
> > > compare "an eeprom device" and "a u-boot environment" of course. But
> > > that's truly what is currently described.
> > >
> > > * Current situation
> > >
> > > Flash device -> U-Boot env layout -> NVMEM cells
>
> Isn't it?:
>
> Flash device -> fixed-partitions -> U-Boot env layout -> NVMEM cells
>
> > >
> > > * Improved situation
> > >
> > > Any storage device -> NVMEM -> U-Boot env layout -> NVMEM cells
>
> Why is this better? We don't need a container to say 'this is NVMEM
> stuff' or 'this is MTD stuff'. 'U-Boot env layout' can tell us 'this is
> NVMEM stuff' or whatever the kernel decides in the future.
Yes, I also want the U-boot env layout to tell us "this is nvmem
stuff". But that's not the case today. Today, it says "this is NVMEM
stuff on top of mtd stuff". This was a mistake in the first place, but
this compatible is heavily tight to mtd and cannot work on anything
else. And correcting this is IMO the right direction.
> > > The latter is of course the most relevant description as we expect
> > > storage devices to expose a storage-agnostic interface (NVMEM in
> > > this case) which can then be parsed (by NVMEM layouts) in a storage
> > > agnostic way.
> > >
> > > In the current case, the current U-Boot env binding tells people to
> > > declare the env layout on top of a flash device (only). The current
> > > description also expects a partition node which is typical to flash
> > > devices. Whereas what we should have described in the first place is a
> > > layout that applies on any kind of NVMEM device.
> > >
> > > Bonus point: We've been working the last couple years on clarifying
> > > bindings, especially with mtd partitions (with the partitions{}
> > > container) and NVMEM layouts (with the nvmem-layout{} container).
> > > The switch proposed in this patch makes use of the latter, of course.
> >
> > Thanks Miquèl for filling bits I missed in commit description. Despite
> > years in Linux/DT I still struggle with more complex designs
> > documentation.
> >
> >
> > As per Rob's comment I think I see his point and a possible design
> > confusion. If you look from a pure DT perspective then "partitions" and
> > "nvmem-layout" serve a very similar purpose. They describe device's data
> > content structure. For fixed structures we have very similar
> > "fixed-partitions" and "fixed-cells".
> >
> > If we were to design those bindings today I'm wondering if we couldn't
> > have s/partitions/layout/ and s/nvmem-layout/layout/.
>
> Why!? It is just a name, and we can't get rid of the old names. We don't
> need 2 names.
We need 2 names because we are not capturing the same concepts here?
> > Rob: other than having different bindings for MTD vs. NVMEM layouts I
> > think they overall design makes sense. A single device may have content
> > structurized on more than 1 level:
> > 1. You may have fixed layout at top level (multiple partitions)
> > 2. Single partitions may have their own layouts (like U-Boot env data)
>
> Sure. Partitions is for 1 and Layouts is for 2.
>
> > Maybe ideally above should look more like:
> >
> > flash@0 {
> > compatible = "";
> >
> > layout {
> > compatible = "fixed-layout";
>
> Why does 'partitions' and 'fixed-partitions' not work here?
They do, and that's actually what we use. This example just illustrates
another proposal from Rafal. No panic :)
>
> > #address-cells = <1>;
> > #size-cells = <1>;
> >
> > partition@0 {
> > reg = <0x0 0x4>;
> > label = "u-boot";
> > };
> >
> > partition@4 {
> >
Re: [PATCH V3 1/6] dt-bindings: nvmem: layouts: add U-Boot environment variables layout
On Thu, Jan 04, 2024 at 10:10:13AM +0100, Rafał Miłecki wrote:
> On 4.01.2024 08:58, Miquel Raynal wrote:
> > r...@kernel.org wrote on Wed, 3 Jan 2024 17:11:29 -0700:
> > > On Thu, Dec 21, 2023 at 06:34:16PM +0100, Rafał Miłecki wrote:
> > > > From: Rafał Miłecki
> > > >
> > > > U-Boot env data is a way of storing firmware variables. It's a format
> > > > that can be used of top of various storage devices. Its binding should
> > > > be an NVMEM layout instead of a standalone device.
> > > >
> > > > This patch adds layout binding which allows using it on top of MTD NVMEM
> > > > device as well as any other. At the same time it deprecates the old
> > > > combined binding.
> > >
> > > I don't understand the issue. From a DT perspective, there isn't. A
> > > partition is not a device, but is describing the layout of storage
> > > already.
> >
> > Actually I think what Rafał wants to do goes in the right direction but
> > I also understand from a binding perspective it may be a little
> > confusing, even more if we consider "NVMEM" a Linux specific concept.
> >
> > There is today a "u-boot env" NVMEM *device* description which
> > almost sits at the same level as eg. an eeprom device. We cannot
> > compare "an eeprom device" and "a u-boot environment" of course. But
> > that's truly what is currently described.
> >
> > * Current situation
> >
> > Flash device -> U-Boot env layout -> NVMEM cells
Isn't it?:
Flash device -> fixed-partitions -> U-Boot env layout -> NVMEM cells
> >
> > * Improved situation
> >
> > Any storage device -> NVMEM -> U-Boot env layout -> NVMEM cells
Why is this better? We don't need a container to say 'this is NVMEM
stuff' or 'this is MTD stuff'. 'U-Boot env layout' can tell us 'this is
NVMEM stuff' or whatever the kernel decides in the future.
> >
> > The latter is of course the most relevant description as we expect
> > storage devices to expose a storage-agnostic interface (NVMEM in
> > this case) which can then be parsed (by NVMEM layouts) in a storage
> > agnostic way.
> >
> > In the current case, the current U-Boot env binding tells people to
> > declare the env layout on top of a flash device (only). The current
> > description also expects a partition node which is typical to flash
> > devices. Whereas what we should have described in the first place is a
> > layout that applies on any kind of NVMEM device.
> >
> > Bonus point: We've been working the last couple years on clarifying
> > bindings, especially with mtd partitions (with the partitions{}
> > container) and NVMEM layouts (with the nvmem-layout{} container).
> > The switch proposed in this patch makes use of the latter, of course.
>
> Thanks Miquèl for filling bits I missed in commit description. Despite
> years in Linux/DT I still struggle with more complex designs
> documentation.
>
>
> As per Rob's comment I think I see his point and a possible design
> confusion. If you look from a pure DT perspective then "partitions" and
> "nvmem-layout" serve a very similar purpose. They describe device's data
> content structure. For fixed structures we have very similar
> "fixed-partitions" and "fixed-cells".
>
> If we were to design those bindings today I'm wondering if we couldn't
> have s/partitions/layout/ and s/nvmem-layout/layout/.
Why!? It is just a name, and we can't get rid of the old names. We don't
need 2 names.
> Rob: other than having different bindings for MTD vs. NVMEM layouts I
> think they overall design makes sense. A single device may have content
> structurized on more than 1 level:
> 1. You may have fixed layout at top level (multiple partitions)
> 2. Single partitions may have their own layouts (like U-Boot env data)
Sure. Partitions is for 1 and Layouts is for 2.
> Maybe ideally above should look more like:
>
> flash@0 {
> compatible = "";
>
> layout {
> compatible = "fixed-layout";
Why does 'partitions' and 'fixed-partitions' not work here?
> #address-cells = <1>;
> #size-cells = <1>;
>
> partition@0 {
> reg = <0x0 0x4>;
> label = "u-boot";
> };
>
> partition@4 {
> reg = <0x4 0x1>;
> label = "u-boot-env";
>
> layout {
> compatible = "u-boot,env-layout";
> };
> };
>
> partition@5 {
> reg = <0x5 0x10>;
> label = "u-boot";
> };
> };
> };
>
> but I can clearly see a use for nested "layout"s. As I said maybe we
> just shouldn't be so open in calling those MTD or NVMEM devices as that
> is kind of Linux specific.
The overall structure should be agnostic to the subsystem. Specific
compatibles like 'u-boot,env' can be tied to a subsystem.
Maybe some things need to be both MTD and NVMEM. MTD to o
Re: [PATCH V3 1/6] dt-bindings: nvmem: layouts: add U-Boot environment variables layout
On 4.01.2024 08:58, Miquel Raynal wrote:
r...@kernel.org wrote on Wed, 3 Jan 2024 17:11:29 -0700:
On Thu, Dec 21, 2023 at 06:34:16PM +0100, Rafał Miłecki wrote:
From: Rafał Miłecki
U-Boot env data is a way of storing firmware variables. It's a format
that can be used of top of various storage devices. Its binding should
be an NVMEM layout instead of a standalone device.
This patch adds layout binding which allows using it on top of MTD NVMEM
device as well as any other. At the same time it deprecates the old
combined binding.
I don't understand the issue. From a DT perspective, there isn't. A
partition is not a device, but is describing the layout of storage
already.
Actually I think what Rafał wants to do goes in the right direction but
I also understand from a binding perspective it may be a little
confusing, even more if we consider "NVMEM" a Linux specific concept.
There is today a "u-boot env" NVMEM *device* description which
almost sits at the same level as eg. an eeprom device. We cannot
compare "an eeprom device" and "a u-boot environment" of course. But
that's truly what is currently described.
* Current situation
Flash device -> U-Boot env layout -> NVMEM cells
* Improved situation
Any storage device -> NVMEM -> U-Boot env layout -> NVMEM cells
The latter is of course the most relevant description as we expect
storage devices to expose a storage-agnostic interface (NVMEM in
this case) which can then be parsed (by NVMEM layouts) in a storage
agnostic way.
In the current case, the current U-Boot env binding tells people to
declare the env layout on top of a flash device (only). The current
description also expects a partition node which is typical to flash
devices. Whereas what we should have described in the first place is a
layout that applies on any kind of NVMEM device.
Bonus point: We've been working the last couple years on clarifying
bindings, especially with mtd partitions (with the partitions{}
container) and NVMEM layouts (with the nvmem-layout{} container).
The switch proposed in this patch makes use of the latter, of course.
Thanks Miquèl for filling bits I missed in commit description. Despite
years in Linux/DT I still struggle with more complex designs
documentation.
As per Rob's comment I think I see his point and a possible design
confusion. If you look from a pure DT perspective then "partitions" and
"nvmem-layout" serve a very similar purpose. They describe device's data
content structure. For fixed structures we have very similar
"fixed-partitions" and "fixed-cells".
If we were to design those bindings today I'm wondering if we couldn't
have s/partitions/layout/ and s/nvmem-layout/layout/.
Rob: other than having different bindings for MTD vs. NVMEM layouts I
think they overall design makes sense. A single device may have content
structurized on more than 1 level:
1. You may have fixed layout at top level (multiple partitions)
2. Single partitions may have their own layouts (like U-Boot env data)
Maybe ideally above should look more like:
flash@0 {
compatible = "";
layout {
compatible = "fixed-layout";
#address-cells = <1>;
#size-cells = <1>;
partition@0 {
reg = <0x0 0x4>;
label = "u-boot";
};
partition@4 {
reg = <0x4 0x1>;
label = "u-boot-env";
layout {
compatible = "u-boot,env-layout";
};
};
partition@5 {
reg = <0x5 0x10>;
label = "u-boot";
};
};
};
but I can clearly see a use for nested "layout"s. As I said maybe we
just shouldn't be so open in calling those MTD or NVMEM devices as that
is kind of Linux specific.
I'm not sure if we should try renaming "nvmem-layout" to "layout" or
"partitions" in similar way at this point.
Re: [PATCH V3 1/6] dt-bindings: nvmem: layouts: add U-Boot environment variables layout
Hello,
r...@kernel.org wrote on Wed, 3 Jan 2024 17:11:29 -0700:
> On Thu, Dec 21, 2023 at 06:34:16PM +0100, Rafał Miłecki wrote:
> > From: Rafał Miłecki
> >
> > U-Boot env data is a way of storing firmware variables. It's a format
> > that can be used of top of various storage devices. Its binding should
> > be an NVMEM layout instead of a standalone device.
> >
> > This patch adds layout binding which allows using it on top of MTD NVMEM
> > device as well as any other. At the same time it deprecates the old
> > combined binding.
>
> I don't understand the issue. From a DT perspective, there isn't. A
> partition is not a device, but is describing the layout of storage
> already.
Actually I think what Rafał wants to do goes in the right direction but
I also understand from a binding perspective it may be a little
confusing, even more if we consider "NVMEM" a Linux specific concept.
There is today a "u-boot env" NVMEM *device* description which
almost sits at the same level as eg. an eeprom device. We cannot
compare "an eeprom device" and "a u-boot environment" of course. But
that's truly what is currently described.
* Current situation
Flash device -> U-Boot env layout -> NVMEM cells
* Improved situation
Any storage device -> NVMEM -> U-Boot env layout -> NVMEM cells
The latter is of course the most relevant description as we expect
storage devices to expose a storage-agnostic interface (NVMEM in
this case) which can then be parsed (by NVMEM layouts) in a storage
agnostic way.
In the current case, the current U-Boot env binding tells people to
declare the env layout on top of a flash device (only). The current
description also expects a partition node which is typical to flash
devices. Whereas what we should have described in the first place is a
layout that applies on any kind of NVMEM device.
Bonus point: We've been working the last couple years on clarifying
bindings, especially with mtd partitions (with the partitions{}
container) and NVMEM layouts (with the nvmem-layout{} container).
The switch proposed in this patch makes use of the latter, of course.
Thanks,
Miquèl
Re: [PATCH V3 1/6] dt-bindings: nvmem: layouts: add U-Boot environment variables layout
On Thu, Dec 21, 2023 at 06:34:16PM +0100, Rafał Miłecki wrote: > From: Rafał Miłecki > > U-Boot env data is a way of storing firmware variables. It's a format > that can be used of top of various storage devices. Its binding should > be an NVMEM layout instead of a standalone device. > > This patch adds layout binding which allows using it on top of MTD NVMEM > device as well as any other. At the same time it deprecates the old > combined binding. I don't understand the issue. From a DT perspective, there isn't. A partition is not a device, but is describing the layout of storage already. Rob
[PATCH V3 1/6] dt-bindings: nvmem: layouts: add U-Boot environment variables layout
From: Rafał Miłecki
U-Boot env data is a way of storing firmware variables. It's a format
that can be used of top of various storage devices. Its binding should
be an NVMEM layout instead of a standalone device.
This patch adds layout binding which allows using it on top of MTD NVMEM
device as well as any other. At the same time it deprecates the old
combined binding.
Signed-off-by: Rafał Miłecki
---
V2: Add "-layout" suffix to compatibles to avoid conflict
.../nvmem/layouts/u-boot,env-layout.yaml | 55 +++
.../devicetree/bindings/nvmem/u-boot,env.yaml | 6 ++
2 files changed, 61 insertions(+)
create mode 100644
Documentation/devicetree/bindings/nvmem/layouts/u-boot,env-layout.yaml
diff --git
a/Documentation/devicetree/bindings/nvmem/layouts/u-boot,env-layout.yaml
b/Documentation/devicetree/bindings/nvmem/layouts/u-boot,env-layout.yaml
new file mode 100644
index ..3b4d8f2a44e1
--- /dev/null
+++ b/Documentation/devicetree/bindings/nvmem/layouts/u-boot,env-layout.yaml
@@ -0,0 +1,55 @@
+# SPDX-License-Identifier: GPL-2.0 OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/nvmem/layouts/u-boot,env-layout.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: NVMEM layout of U-Boot environment variables
+
+maintainers:
+ - Rafał Miłecki
+
+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).
+
+properties:
+ compatible:
+oneOf:
+ - description: A standalone env data block
+const: u-boot,env-layout
+ - description: Two redundant blocks with active one flagged
+const: u-boot,env-redundant-bool-layout
+ - description: Two redundant blocks with active having higher counter
+const: u-boot,env-redundant-count-layout
+ - description: Broadcom's variant with custom header
+const: brcm,env-layout
+
+additionalProperties: false
+
+examples:
+ - |
+partitions {
+compatible = "fixed-partitions";
+#address-cells = <1>;
+#size-cells = <1>;
+
+partition@0 {
+reg = <0x0 0x4>;
+label = "u-boot";
+read-only;
+};
+
+partition@4 {
+reg = <0x4 0x1>;
+label = "u-boot-env";
+
+nvmem-layout {
+compatible = "u-boot,env-layout";
+};
+};
+};
diff --git a/Documentation/devicetree/bindings/nvmem/u-boot,env.yaml
b/Documentation/devicetree/bindings/nvmem/u-boot,env.yaml
index 9c36afc7084b..6c2a3ca5f051 100644
--- a/Documentation/devicetree/bindings/nvmem/u-boot,env.yaml
+++ b/Documentation/devicetree/bindings/nvmem/u-boot,env.yaml
@@ -26,9 +26,15 @@ description: |
Variables can be defined as NVMEM device subnodes.
+ Introduction of NVMEM layouts exposed a limitation of this binding design.
+ Description of NVMEM data content should be separated from NVMEM devices.
+ Since the introduction of U-Boot env data layout this binding is deprecated.
+
maintainers:
- Rafał Miłecki
+deprecated: true
+
properties:
compatible:
oneOf:
--
2.35.3
