linux-kernel - [PATCH v2 3/7] firmware: dmi: Read additional information when decoding DMI table

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Message-ID: <20251216123354.9219-4-superm1@kernel.org>
Date: Tue, 16 Dec 2025 06:33:50 -0600
From: "Mario Limonciello (AMD)" <superm1@...nel.org>
To: Yazen Ghannam <yazen.ghannam@....com>,
	x86@...nel.org (maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)),
	Jean Delvare <jdelvare@...e.com>
Cc: Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	"H . Peter Anvin" <hpa@...or.com>,
	linux-kernel@...r.kernel.org,
	"Mario Limonciello (AMD)" <superm1@...nel.org>
Subject: [PATCH v2 3/7] 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.  Save these entries when
decoding the DMI tables.

Signed-off-by: Mario Limonciello (AMD) <superm1@...nel.org>
---
v2:
 * Drop some unneeded variables (LKP robot)
 * Allow any length strings, not just 5 and longer
---
 drivers/firmware/dmi_scan.c | 38 +++++++++++++++++++++++++++++++++++++
 include/linux/dmi.h         |  7 +++++++
 2 files changed, 45 insertions(+)

diff --git a/drivers/firmware/dmi_scan.c b/drivers/firmware/dmi_scan.c
index 80aded4c778bc..ec84fe3935c1e 100644
--- a/drivers/firmware/dmi_scan.c
+++ b/drivers/firmware/dmi_scan.c
@@ -393,6 +393,40 @@ static void __init dmi_save_dev_pciaddr(int instance, int segment, int bus,
 	list_add(&dev->dev.list, &dmi_devices);
 }
 
+static void __init dmi_save_additional(const struct dmi_additional_info *info)
+{
+	const u8 *data;
+	int i;
+
+	if (!info || info->header.length < 5 + info->count * 5)
+		return;
+
+	data = info->entries;
+
+	for (i = 0; i < info->count; i++) {
+		u8 string_num = data[i * 5 + 4];
+		const char *string_ptr;
+		char *value;
+		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;
+
+		value = dmi_alloc(len + 1);
+		if (!value)
+			continue;
+
+		strscpy(value, string_ptr, len + 1);
+
+		dmi_save_one_device(DMI_DEV_TYPE_ADDITIONAL, value);
+	}
+}
+
 static void __init dmi_save_extended_devices(const struct dmi_header *dm)
 {
 	const char *name;
@@ -526,8 +560,12 @@ 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_save_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 a809b5095c259..3fc3d334b321d 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 {
@@ -87,6 +88,12 @@ 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