[PATCH v3] boot/bootfdt: Add smbios3-entrypoint to FDT for non-EFI boots
Simon Glass
sjg at chromium.org
Wed Nov 19 18:34:50 CET 2025
Hi Adriana,
On Wed, 19 Nov 2025 at 06:06, Adriana Nicolae <adriana at arista.com> wrote:
>
> 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();
Please don't add weak functions. We can use gd_smbios_start() here.
> + 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
Please add one
> 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)) {
This is a strange thing to do. If that is not enabled then we should
skip the test, i.e. return -EAGAIN at the top.
> + 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");
no need; this is a temporary blob
> +
> +out:
> + free(blob);
> +
> + return 0;
> +}
> +DM_TEST(dm_test_fdt_chosen_smbios, UTF_SCAN_PDATA | UTF_SCAN_FDT);
> \ No newline at end of file
Please add one
Test looks good other than my nits.
Regards,
Simon
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