linux-kernel - [PATCH v3 5/5] firmware: dmi: Read additional information when decoding DMI table

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Message-ID: <20260110134835.1296600-6-superm1@kernel.org>
Date: Sat, 10 Jan 2026 07:48:34 -0600
From: "Mario Limonciello (AMD)" <superm1@...nel.org>
To: Yazen Ghannam <yazen.ghannam@....com>,
	Jean Delvare <jdelvare@...e.com>
Cc: linux-kernel@...r.kernel.org,
	Borislav Petkov <bp@...en8.de>,
	"Mario Limonciello (AMD)" <superm1@...nel.org>
Subject: [PATCH v3 5/5] firmware: dmi: Read additional information when decoding DMI table

Type 40 entries (Additional information) are summarized in section
7.41 as part of the SMBIOS specification.  These entries aren't
all interesting enough to save, but on some AMD Zen systems the
AGESA version is stored here and can be useful to save into
debugging logs for cross referencing issues when reported.

Signed-off-by: Mario Limonciello (AMD) <superm1@...nel.org>
---
v3:
 * Merge patch to show AGESA version (Jean)
 * Don't save strings (Jean)
 * Avoid out of bounds (Jean)
---
 drivers/firmware/dmi_scan.c | 32 ++++++++++++++++++++++++++++++++
 include/linux/dmi.h         |  7 +++++++
 2 files changed, 39 insertions(+)

diff --git a/drivers/firmware/dmi_scan.c b/drivers/firmware/dmi_scan.c
index caa09ddf0dfa7..e1125d011d24b 100644
--- a/drivers/firmware/dmi_scan.c
+++ b/drivers/firmware/dmi_scan.c
@@ -396,6 +396,34 @@ static void __init dmi_save_dev_pciaddr(int instance, int segment, int bus,
 	list_add(&dev->dev.list, &dmi_devices);
 }
 
+static void __init dmi_scan_additional(const struct dmi_additional_info *info)
+{
+	const u8 *data;
+	int i;
+
+	if (!info || info->header.length < 5)
+		return;
+
+	data = info->entries;
+
+	for (i = 0; i < info->count; i++) {
+		u8 string_num = data[i * 5 + 4];
+		const char *string_ptr;
+		int len;
+
+		string_ptr = dmi_string_nosave(&info->header, string_num);
+		if (!string_ptr || !*string_ptr)
+			continue;
+
+		len = strlen(string_ptr);
+		if (len == 0)
+			continue;
+
+		if (!strncmp(string_ptr, "AGESA", 5))
+			pr_info("%s\n", string_ptr);
+	}
+}
+
 static void __init dmi_save_extended_devices(const struct dmi_header *dm)
 {
 	const char *name;
@@ -529,8 +557,12 @@ static void __init dmi_decode(const struct dmi_header *dm, void *dummy)
 	case DMI_ENTRY_IPMI_DEV:
 		dmi_save_ipmi_device(dm);
 		break;
+	case DMI_ENTRY_ADDITIONAL:
+		dmi_scan_additional((const struct dmi_additional_info *)dm);
+		break;
 	case DMI_ENTRY_ONBOARD_DEV_EXT:
 		dmi_save_extended_devices(dm);
+		break;
 	}
 }
 
diff --git a/include/linux/dmi.h b/include/linux/dmi.h
index 2eedf44e68012..4bb1b7882237f 100644
--- a/include/linux/dmi.h
+++ b/include/linux/dmi.h
@@ -24,6 +24,7 @@ enum dmi_device_type {
 	DMI_DEV_TYPE_OEM_STRING = -2,
 	DMI_DEV_TYPE_DEV_ONBOARD = -3,
 	DMI_DEV_TYPE_DEV_SLOT = -4,
+	DMI_DEV_TYPE_ADDITIONAL = -5,
 };
 
 enum dmi_entry_type {
@@ -91,6 +92,12 @@ struct dmi_device {
 	void *device_data;	/* Type specific data */
 };
 
+struct dmi_additional_info {
+	struct dmi_header header;
+	u8 count;
+	u8 entries[];
+} __packed;
+
 #ifdef CONFIG_DMI
 
 struct dmi_dev_onboard {
-- 
2.43.0