[PATCH v2 1/2] environment: support DT-compatible-specific overlays

[PATCH v2 1/2] environment: support DT-compatible-specific overlays

[Ahmad Fatoum]

From: Ahmad Fatoum <a.fatoum@barebox.org>

Board-specific environments are registered from board code via
defaultenv_append_directory(), but this isn't possible when using
CONFIG_DEFAULT_ENVIRONMENT_PATH with an external environment.

Add support for a match.of_compatible/ directory convention within
the default environment. Subdirectories named after DT root compatible
strings are overlaid onto /env from most generic to most specific
after the default environment is loaded. The match.of_compatible/
directory is removed afterwards to keep /env clean.

Example layout in CONFIG_DEFAULT_ENVIRONMENT_PATH:

  barebox-defaultenv/
    nv/boot.default
    match.of_compatible/
      fsl,imx8mm/
        nv/boot.default
      fsl,imx8mm-evk/
        nv/boot.default

For compatible = "fsl,imx8mm-evk", "fsl,imx8mm":
  1. fsl,imx8mm/     overlay applied first  (most generic)
  2. fsl,imx8mm-evk/ overlay applied second (most specific)

Signed-off-by: Ahmad Fatoum <a.fatoum@barebox.org>
---
v1 -> v2:
  - Fix typo in commit message (Marco)
  - Add documentation for the feature (Marco)
---
 Documentation/user/defaultenv-2.rst | 29 ++++++++++++++++++
 common/startup.c                    | 47 +++++++++++++++++++++++++++++
 2 files changed, 76 insertions(+)

diff --git a/Documentation/user/defaultenv-2.rst b/Documentation/user/defaultenv-2.rst
index e5cb4a51bfad..2564eb959fcc 100644
--- a/Documentation/user/defaultenv-2.rst
+++ b/Documentation/user/defaultenv-2.rst
@@ -155,3 +155,32 @@ This contains the files to be sourced when barebox detects that the OS
 had requested a specific :ref:`reboot_mode` (via e.g. ``reboot bootloader``
 under Linux). After the ``/env/init`` scripts were executed, barebox will
 ``source /env/bmode/${global.system.reboot_mode.prev}`` if available.
+
+/env/mach.of_compatible/
+------------------------
+
+On devicetree enabled systems, this optional directory may contain
+environment overlays that should be applied onto ``/env``.
+
+Each subdirectory should be named after a device tree root compatible
+string and they will be applied from most generic to most specific match
+after the default environment is loaded.
+The ``match.of_compatible/`` directory is removed afterwards to keep
+``/env`` clean.
+
+For example, given ``CONFIG_DEFAULT_ENVIRONMENT_PATH`` pointing
+at an external ``barebox-defaultenv/`` directory::
+
+  barebox-defaultenv/
+    nv/boot.default     -> kernel-common
+    match.of_compatible/
+      fsl,imx8mm/
+        nv/boot.default -> kernel-mx8mm
+      fsl,imx8mm-evk/
+        nv/boot.default -> kernel-mx8mm-evk
+
+The final ``/env/nv/boot.default`` would be:
+
+- For ``compatible = "fsl,imx8mm-evk", "fsl,imx8mm";``,  ``kernel-mx8mm-evk``
+- For ``compatible = "fsl,imx8mm-evkb", "fsl,imx8mm";``, ``kernel-mx8mm``
+- For ``compatible = "fsl,imx8mp-evk", "fsl,imx8mp";``,  ``kernel-common``
diff --git a/common/startup.c b/common/startup.c
index 2e2b5f820fe9..e630033e3505 100644
--- a/common/startup.c
+++ b/common/startup.c
@@ -46,6 +46,7 @@
 #include <pbl/handoff-data.h>
 #include <libfile.h>
 #include <fuzz.h>
+#include <of.h>
 
 extern initcall_t __barebox_initcalls_start[], __barebox_early_initcalls_end[],
 		  __barebox_initcalls_end[];
@@ -95,6 +96,50 @@ void autoload_external_env(bool endis)
 }
 #endif
 
+static void env_merge_of_compat_overlays(const char *dir)
+{
+	struct device_node *root;
+	const char *compat;
+	struct stat s;
+	char *ofdir, *src;
+	int count;
+
+	root = of_get_root_node();
+	if (!root)
+		return;
+
+	ofdir = xasprintf("%s/match.of_compatible", dir);
+
+	if (stat(ofdir, &s) || !S_ISDIR(s.st_mode))
+		goto out;
+
+	count = of_property_count_strings(root, "compatible");
+
+	/*
+	 * Apply overlays from most generic to most specific, so that
+	 * more specific entries take precedence.
+	 */
+	for (int i = count - 1; i >= 0; i--) {
+		if (of_property_read_string_index(root, "compatible",
+						  i, &compat))
+			continue;
+
+		src = xasprintf("%s/%s", ofdir, compat);
+
+		if (stat(src, &s) == 0 && S_ISDIR(s.st_mode)) {
+			pr_debug("Applying '%s'-compatible environment overlay\n",
+				 compat);
+			copy_recursive(src, dir, 0);
+		}
+
+		free(src);
+	}
+
+	unlink_recursive(ofdir, NULL);
+out:
+	free(ofdir);
+}
+
 static int load_environment(void)
 {
 	const char *default_environment_path;
@@ -115,6 +160,8 @@ static int load_environment(void)
 		pr_info("external environment support %s. Using default environment\n",
 			IS_ENABLED(CONFIG_ENV_HANDLING) ? "disallowed" : "disabled");
 
+	env_merge_of_compat_overlays("/env");
+
 	nvvar_load();
 
 	return 0;
-- 
2.47.3

[PATCH v2 2/2] sandbox: add a match.of_compatible directory to exercise the feature

[Ahmad Fatoum]

From: Ahmad Fatoum <a.fatoum@barebox.org>

The match.of_compatible feature is mostly meant to be used with
environments originating outside barebox.

Nevertheless, switch over sandbox to use it so it gets some coverage.

Signed-off-by: Ahmad Fatoum <a.fatoum@barebox.org>
---
v1 -> v2:
  - no change
---
 arch/sandbox/board/defaultenv-sandbox/data/last-match           | 1 +
 .../match.of_compatible/barebox,not-sandbox/data/last-match     | 1 +
 .../match.of_compatible/barebox,not-sandbox/nv/autoboot         | 1 +
 .../match.of_compatible/barebox,sandbox/data/last-match         | 1 +
 .../match.of_compatible/barebox,sandbox/nv/autoboot             | 1 +
 arch/sandbox/board/defaultenv-sandbox/nv/autoboot               | 2 +-
 6 files changed, 6 insertions(+), 1 deletion(-)
 create mode 100644 arch/sandbox/board/defaultenv-sandbox/data/last-match
 create mode 100644 arch/sandbox/board/defaultenv-sandbox/match.of_compatible/barebox,not-sandbox/data/last-match
 create mode 100644 arch/sandbox/board/defaultenv-sandbox/match.of_compatible/barebox,not-sandbox/nv/autoboot
 create mode 100644 arch/sandbox/board/defaultenv-sandbox/match.of_compatible/barebox,sandbox/data/last-match
 create mode 100644 arch/sandbox/board/defaultenv-sandbox/match.of_compatible/barebox,sandbox/nv/autoboot

diff --git a/arch/sandbox/board/defaultenv-sandbox/data/last-match b/arch/sandbox/board/defaultenv-sandbox/data/last-match
new file mode 100644
index 000000000000..df967b96a579
--- /dev/null
+++ b/arch/sandbox/board/defaultenv-sandbox/data/last-match
@@ -0,0 +1 @@
+base
diff --git a/arch/sandbox/board/defaultenv-sandbox/match.of_compatible/barebox,not-sandbox/data/last-match b/arch/sandbox/board/defaultenv-sandbox/match.of_compatible/barebox,not-sandbox/data/last-match
new file mode 100644
index 000000000000..b175a503912d
--- /dev/null
+++ b/arch/sandbox/board/defaultenv-sandbox/match.of_compatible/barebox,not-sandbox/data/last-match
@@ -0,0 +1 @@
+barebox,not-sandbox
diff --git a/arch/sandbox/board/defaultenv-sandbox/match.of_compatible/barebox,not-sandbox/nv/autoboot b/arch/sandbox/board/defaultenv-sandbox/match.of_compatible/barebox,not-sandbox/nv/autoboot
new file mode 100644
index 000000000000..36ef4c374d25
--- /dev/null
+++ b/arch/sandbox/board/defaultenv-sandbox/match.of_compatible/barebox,not-sandbox/nv/autoboot
@@ -0,0 +1 @@
+boot
diff --git a/arch/sandbox/board/defaultenv-sandbox/match.of_compatible/barebox,sandbox/data/last-match b/arch/sandbox/board/defaultenv-sandbox/match.of_compatible/barebox,sandbox/data/last-match
new file mode 100644
index 000000000000..80fdf1459eee
--- /dev/null
+++ b/arch/sandbox/board/defaultenv-sandbox/match.of_compatible/barebox,sandbox/data/last-match
@@ -0,0 +1 @@
+barebox,sandbox
diff --git a/arch/sandbox/board/defaultenv-sandbox/match.of_compatible/barebox,sandbox/nv/autoboot b/arch/sandbox/board/defaultenv-sandbox/match.of_compatible/barebox,sandbox/nv/autoboot
new file mode 100644
index 000000000000..f7d13fd04662
--- /dev/null
+++ b/arch/sandbox/board/defaultenv-sandbox/match.of_compatible/barebox,sandbox/nv/autoboot
@@ -0,0 +1 @@
+abort
diff --git a/arch/sandbox/board/defaultenv-sandbox/nv/autoboot b/arch/sandbox/board/defaultenv-sandbox/nv/autoboot
index f7d13fd04662..36ef4c374d25 100644
--- a/arch/sandbox/board/defaultenv-sandbox/nv/autoboot
+++ b/arch/sandbox/board/defaultenv-sandbox/nv/autoboot
@@ -1 +1 @@
-abort
+boot
-- 
2.47.3

Re: [PATCH v2 1/2] environment: support DT-compatible-specific overlays

[Marco Felsch]

On 26-04-13, Ahmad Fatoum wrote:
> From: Ahmad Fatoum <a.fatoum@barebox.org>
> 
> Board-specific environments are registered from board code via
> defaultenv_append_directory(), but this isn't possible when using
> CONFIG_DEFAULT_ENVIRONMENT_PATH with an external environment.
> 
> Add support for a match.of_compatible/ directory convention within
> the default environment. Subdirectories named after DT root compatible
> strings are overlaid onto /env from most generic to most specific
> after the default environment is loaded. The match.of_compatible/
> directory is removed afterwards to keep /env clean.
> 
> Example layout in CONFIG_DEFAULT_ENVIRONMENT_PATH:
> 
>   barebox-defaultenv/
>     nv/boot.default
>     match.of_compatible/
>       fsl,imx8mm/
>         nv/boot.default
>       fsl,imx8mm-evk/
>         nv/boot.default
> 
> For compatible = "fsl,imx8mm-evk", "fsl,imx8mm":
>   1. fsl,imx8mm/     overlay applied first  (most generic)
>   2. fsl,imx8mm-evk/ overlay applied second (most specific)
> 
> Signed-off-by: Ahmad Fatoum <a.fatoum@barebox.org>

Reviewed-by: Marco Felsch <m.felsch@pengutronix.de>

Re: [PATCH v2 1/2] environment: support DT-compatible-specific overlays

[Sascha Hauer]

On Mon, 13 Apr 2026 15:43:52 +0200, Ahmad Fatoum wrote:
> Board-specific environments are registered from board code via
> defaultenv_append_directory(), but this isn't possible when using
> CONFIG_DEFAULT_ENVIRONMENT_PATH with an external environment.
> 
> Add support for a match.of_compatible/ directory convention within
> the default environment. Subdirectories named after DT root compatible
> strings are overlaid onto /env from most generic to most specific
> after the default environment is loaded. The match.of_compatible/
> directory is removed afterwards to keep /env clean.
> 
> [...]

Applied, thanks!

[1/2] environment: support DT-compatible-specific overlays
      https://git.pengutronix.de/cgit/barebox/commit/?id=29bd991c06f4 (link may not be stable)
[2/2] sandbox: add a match.of_compatible directory to exercise the feature
      https://git.pengutronix.de/cgit/barebox/commit/?id=b071c63dc663 (link may not be stable)

Best regards,
-- 
Sascha Hauer <s.hauer@pengutronix.de>