[PATCH v3] boot/bootfdt: Add smbios3-entrypoint to FDT for non-EFI boots
Adriana Nicolae
adriana at arista.com
Wed Nov 19 14:06:09 CET 2025
From: adriana <adriana at arista.com>
The Linux kernel can discover SMBIOS tables through two primary methods:
1. Via EFI tables, when using EFI boot;
2. Via the 'smbios3-entrypoint' property in the /chosen node of the
device tree.
When U-Boot boots a Linux kernel using a non-EFI command ("bootm",
"bootz", or "booti"), the kernel relies on the device tree to detect
the hardware. If SMBIOS tables are available in U-Boot, they should
be passed to the kernel via this device tree property.
This patch modifies boot_fdt_prepare(), to inject the SMBIOSv3 table
address into the device tree if there is a table generated by U-boot.
The "board_fdt_chosen_smbios" is weak in order to leave the possibilty
for specific boards to select custom SMBIOS addresses.
The changes in this patch are added in the context of supporting this
device tree property in linux kernel:
https://lkml.org/lkml/2025/10/24/1393
Device tree schema was updated to include the "smbios3-entrypoint" node
in pull request: https://github.com/devicetree-org/dt-schema/pull/177
Signed-off-by: Adriana Nicolae <adriana at arista.com>
---
Changes in v3:
- Moved "board_fdt_chosen_smbios" function to lib/smbios.c
- Return physical address of smbios entry and use map_sysmem to
access the entry point;
- Removed check for config enabled and added check for
GENERATE_SMBIOS_TABLE;
- Add test to check that smbios entry address is added into fdt;
Changes in v2:
- Renamed device tree property to "smbios3-entrypoint".
- Removed redundant check for CONFIG_SMBIOS.
---
boot/fdt_support.c | 19 +++++++++++++++++
include/smbios.h | 10 +++++++++
lib/smbios.c | 38 +++++++++++++++++++++++++++++++++
test/dm/fdtdec.c | 52 ++++++++++++++++++++++++++++++++++++++++++++++
4 files changed, 119 insertions(+)
diff --git a/boot/fdt_support.c b/boot/fdt_support.c
index 92f2f534ee0..7da6e7cb2b3 100644
--- a/boot/fdt_support.c
+++ b/boot/fdt_support.c
@@ -27,6 +27,7 @@
#include <fdtdec.h>
#include <version.h>
#include <video.h>
+#include <smbios.h>
DECLARE_GLOBAL_DATA_PTR;
@@ -333,6 +334,7 @@ int fdt_chosen(void *fdt)
int nodeoffset;
int err;
const char *str; /* used to set string properties */
+ ulong smbiosaddr; /* SMBIOS table address */
err = fdt_check_header(fdt);
if (err < 0) {
@@ -387,6 +389,23 @@ int fdt_chosen(void *fdt)
return err;
}
+ if (CONFIG_IS_ENABLED(GENERATE_SMBIOS_TABLE)) {
+ /* Inject SMBIOS address when we have a valid address.
+ * This is useful for systems using booti/bootm instead of bootefi.
+ * Failure to set this property is non-fatal, we only generate a
+ * warning.
+ */
+ smbiosaddr = board_fdt_chosen_smbios();
+ if (smbiosaddr) {
+ err = fdt_setprop_u64(fdt, nodeoffset, "smbios3-entrypoint",
+ smbiosaddr);
+ if (err < 0) {
+ printf("WARNING: could not set smbios3-entrypoint %s.\n",
+ fdt_strerror(err));
+ }
+ }
+ }
+
return fdt_fixup_stdout(fdt, nodeoffset);
}
diff --git a/include/smbios.h b/include/smbios.h
index b5fed57aba2..c37d79aa530 100644
--- a/include/smbios.h
+++ b/include/smbios.h
@@ -383,4 +383,14 @@ int smbios_update_version_full(void *smbios_tab, const char *version);
void smbios_prepare_measurement(const struct smbios3_entry *entry,
struct smbios_header *header);
+/**
+ * board_fdt_chosen_smbios() - Provide SMBIOS address for /chosen node
+ *
+ * This function is called by fdt_chosen() to get the SMBIOS table address
+ * that should be added to the /chosen node for non-UEFI boot scenarios.
+ *
+ * Return: Physical address of SMBIOS table, or 0 if not available
+ */
+ulong board_fdt_chosen_smbios(void);
+
#endif /* _SMBIOS_H_ */
diff --git a/lib/smbios.c b/lib/smbios.c
index b8c2846277a..45ae2d11009 100644
--- a/lib/smbios.c
+++ b/lib/smbios.c
@@ -980,3 +980,41 @@ ulong write_smbios_table(ulong addr)
return addr;
}
+
+/**
+ * board_fdt_chosen_smbios - boards may override this function to provide
+ * specific SMBIOS address
+ */
+__weak ulong board_fdt_chosen_smbios(void)
+{
+ ulong ret = 0;
+ const struct smbios3_entry *entry;
+
+ ret = gd->arch.smbios_start;
+ if (!ret)
+ return 0;
+
+ /* Verify this is SMBIOS 3 */
+ entry = map_sysmem(ret, sizeof(struct smbios3_entry));
+
+ /* Check for "_SM3_" signature */
+ if (memcmp(entry->anchor, "_SM3_", 5) != 0) {
+ printf("SMBIOS: Not version 3, skipping DTB injection\n");
+ ret = 0;
+ goto out;
+ }
+
+ /* Verify entry point length and version */
+ if (entry->length < sizeof(struct smbios3_entry)) {
+ printf("SMBIOS: Invalid entry length %d\n", entry->length);
+ ret = 0;
+ goto out;
+ }
+
+ printf("SMBIOS: Found version %d.%d at 0x%llx\n",
+ entry->major_ver, entry->minor_ver, (u64)ret);
+
+out:
+ unmap_sysmem(entry);
+ return ret;
+}
\ No newline at end of file
diff --git a/test/dm/fdtdec.c b/test/dm/fdtdec.c
index 1f24f1d5dff..6d695a84f5a 100644
--- a/test/dm/fdtdec.c
+++ b/test/dm/fdtdec.c
@@ -7,6 +7,9 @@
#include <asm/global_data.h>
#include <dm/of_extra.h>
#include <dm/test.h>
+#include <fdt_support.h>
+#include <mapmem.h>
+#include <smbios.h>
#include <test/ut.h>
DECLARE_GLOBAL_DATA_PTR;
@@ -129,3 +132,52 @@ static int dm_test_fdtdec_add_reserved_memory(struct unit_test_state *uts)
}
DM_TEST(dm_test_fdtdec_add_reserved_memory,
UTF_SCAN_PDATA | UTF_SCAN_FDT | UTF_FLAT_TREE);
+
+static int dm_test_fdt_chosen_smbios(struct unit_test_state *uts)
+{
+ void *blob;
+ ulong val;
+ struct smbios3_entry *entry;
+ int chosen, blob_sz;
+ const fdt64_t *prop;
+
+ blob_sz = fdt_totalsize(gd->fdt_blob) + 128;
+ blob = malloc(blob_sz);
+ ut_assertnonnull(blob);
+
+ /* Make a writable copy of the fdt blob */
+ ut_assertok(fdt_open_into(gd->fdt_blob, blob, blob_sz));
+
+ /* Mock SMBIOS table */
+ entry = map_sysmem(gd->arch.smbios_start, sizeof(struct smbios3_entry));
+ memcpy(entry->anchor, "_SM3_", 5);
+ entry->length = sizeof(struct smbios3_entry);
+ unmap_sysmem(entry);
+
+ /* Force fdt_chosen to run */
+ ut_assertok(fdt_chosen(blob));
+
+ chosen = fdt_path_offset(blob, "/chosen");
+ ut_assert(chosen >= 0);
+
+ /* Verify the property exists only when GENERATE_SMBIOS_TABLE */
+ prop = fdt_getprop(blob, chosen, "smbios3-entrypoint", NULL);
+ if (!CONFIG_IS_ENABLED(GENERATE_SMBIOS_TABLE)) {
+ ut_assertnull(prop);
+ goto out;
+ }
+ ut_assertnonnull(prop);
+
+ /* Verify the property matches smbios_start */
+ val = fdt64_to_cpu(*prop);
+ ut_asserteq_64(gd->arch.smbios_start, val);
+
+ /* Remove property */
+ fdt_delprop(blob, chosen, "smbios3-entrypoint");
+
+out:
+ free(blob);
+
+ return 0;
+}
+DM_TEST(dm_test_fdt_chosen_smbios, UTF_SCAN_PDATA | UTF_SCAN_FDT);
\ No newline at end of file
--
2.51.0
More information about the U-Boot
mailing list