[PATCH v3 0/5] Parse SMBIOS additional entries

[PATCH v3 0/5] Parse SMBIOS additional entries

[Mario Limonciello (AMD)]

The SMBIOS additional entries on AMD Zen4+ systems running an AGESA
based BIOS contain information about the AGESA version which can be
useful for matching the software stack when debugging an issue.

Add support for parsing this from SMBIOS tables and output it into
the logs at bootup.  Additionally export the information to debugfs
in case users are interested in any other strings.

v3:
 * Drop / merge patches from feedback
 * Don't save additional strings, only show AGESA string if found

Mario Limonciello (1):
  firmware: dmi: Add pr_fmt() for dmi_scan.c

Mario Limonciello (AMD) (4):
  firmware: dmi: Correct an indexing error in dmi.h
  firmware: dmi: Adjust dmi_decode() to use enums
  firmware: dmi: Add missing DMI entry types
  firmware: dmi: Read additional information when decoding DMI table

 drivers/firmware/dmi_scan.c | 61 +++++++++++++++++++++++++++++--------
 include/linux/dmi.h         | 12 ++++++++
 2 files changed, 60 insertions(+), 13 deletions(-)

-- 
2.43.0

[PATCH v3 1/5] firmware: dmi: Correct an indexing error in dmi.h

[Mario Limonciello (AMD)]

The entries later in `enum dmi_entry_type` don't match the SMBIOS
specification.  The entry for type 33: `64-Bit Memory Error Information`
is not present and thus the index for all later entries is incorrect.

Add the missing type 33 entry.

Fixes: 93c890dbe5287 ("firmware: Add DMI entry types to the headers")
Link: https://www.dmtf.org/sites/default/files/standards/documents/DSP0134_3.4.0a.pdf
Reviewed-by: Yazen Ghannam <yazen.ghannam@amd.com>
Signed-off-by: Mario Limonciello (AMD) <superm1@kernel.org>
---
v3:
 * Rename to DMI_ENTRY_64_MEM_ERROR (Jean)
---
 include/linux/dmi.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/include/linux/dmi.h b/include/linux/dmi.h
index 927f8a8b7a1dd..32b2529a73301 100644
--- a/include/linux/dmi.h
+++ b/include/linux/dmi.h
@@ -60,6 +60,7 @@ enum dmi_entry_type {
 	DMI_ENTRY_OOB_REMOTE_ACCESS,
 	DMI_ENTRY_BIS_ENTRY,
 	DMI_ENTRY_SYSTEM_BOOT,
+	DMI_ENTRY_64_MEM_ERROR,
 	DMI_ENTRY_MGMT_DEV,
 	DMI_ENTRY_MGMT_DEV_COMPONENT,
 	DMI_ENTRY_MGMT_DEV_THRES,
-- 
2.43.0

[PATCH v3 2/5] firmware: dmi: Adjust dmi_decode() to use enums

[Mario Limonciello (AMD)]

dmi_decode() has hardcoded values with comments for each DMI entry
type. The same information is already in dmi.h though, so drop the
comments and use the definitions instead.

Reviewed-by: Jean Delvare <jdelvare@suse.de>
Reviewed-by: Yazen Ghannam <yazen.ghannam@amd.com>
Signed-off-by: Mario Limonciello (AMD) <superm1@kernel.org>
---
v3:
 * pick up tag (Jean)
---
 drivers/firmware/dmi_scan.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/drivers/firmware/dmi_scan.c b/drivers/firmware/dmi_scan.c
index 70d39adf50dca..80aded4c778bc 100644
--- a/drivers/firmware/dmi_scan.c
+++ b/drivers/firmware/dmi_scan.c
@@ -484,14 +484,14 @@ static void __init dmi_memdev_walk(void)
 static void __init dmi_decode(const struct dmi_header *dm, void *dummy)
 {
 	switch (dm->type) {
-	case 0:		/* BIOS Information */
+	case DMI_ENTRY_BIOS:
 		dmi_save_ident(dm, DMI_BIOS_VENDOR, 4);
 		dmi_save_ident(dm, DMI_BIOS_VERSION, 5);
 		dmi_save_ident(dm, DMI_BIOS_DATE, 8);
 		dmi_save_release(dm, DMI_BIOS_RELEASE, 21);
 		dmi_save_release(dm, DMI_EC_FIRMWARE_RELEASE, 23);
 		break;
-	case 1:		/* System Information */
+	case DMI_ENTRY_SYSTEM:
 		dmi_save_ident(dm, DMI_SYS_VENDOR, 4);
 		dmi_save_ident(dm, DMI_PRODUCT_NAME, 5);
 		dmi_save_ident(dm, DMI_PRODUCT_VERSION, 6);
@@ -500,33 +500,33 @@ static void __init dmi_decode(const struct dmi_header *dm, void *dummy)
 		dmi_save_ident(dm, DMI_PRODUCT_SKU, 25);
 		dmi_save_ident(dm, DMI_PRODUCT_FAMILY, 26);
 		break;
-	case 2:		/* Base Board Information */
+	case DMI_ENTRY_BASEBOARD:
 		dmi_save_ident(dm, DMI_BOARD_VENDOR, 4);
 		dmi_save_ident(dm, DMI_BOARD_NAME, 5);
 		dmi_save_ident(dm, DMI_BOARD_VERSION, 6);
 		dmi_save_ident(dm, DMI_BOARD_SERIAL, 7);
 		dmi_save_ident(dm, DMI_BOARD_ASSET_TAG, 8);
 		break;
-	case 3:		/* Chassis Information */
+	case DMI_ENTRY_CHASSIS:
 		dmi_save_ident(dm, DMI_CHASSIS_VENDOR, 4);
 		dmi_save_type(dm, DMI_CHASSIS_TYPE, 5);
 		dmi_save_ident(dm, DMI_CHASSIS_VERSION, 6);
 		dmi_save_ident(dm, DMI_CHASSIS_SERIAL, 7);
 		dmi_save_ident(dm, DMI_CHASSIS_ASSET_TAG, 8);
 		break;
-	case 9:		/* System Slots */
+	case DMI_ENTRY_SYSTEM_SLOT:
 		dmi_save_system_slot(dm);
 		break;
-	case 10:	/* Onboard Devices Information */
+	case DMI_ENTRY_ONBOARD_DEVICE:
 		dmi_save_devices(dm);
 		break;
-	case 11:	/* OEM Strings */
+	case DMI_ENTRY_OEMSTRINGS:
 		dmi_save_oem_strings_devices(dm);
 		break;
-	case 38:	/* IPMI Device Information */
+	case DMI_ENTRY_IPMI_DEV:
 		dmi_save_ipmi_device(dm);
 		break;
-	case 41:	/* Onboard Devices Extended Information */
+	case DMI_ENTRY_ONBOARD_DEV_EXT:
 		dmi_save_extended_devices(dm);
 	}
 }
-- 
2.43.0

[PATCH v3 3/5] firmware: dmi: Add missing DMI entry types

[Mario Limonciello (AMD)]

Type 42 through type 46 entry types are missing from the
definitions in the dmi_entry_type enum.

Link: https://www.dmtf.org/sites/default/files/standards/documents/DSP0134_3.7.1.pdf
Suggested-by: Yazen Ghannam <yazen.ghannam@amd.com>
Reviewed-by: Jean Delvare <jdelvare@suse.de>
Signed-off-by: Mario Limonciello (AMD) <superm1@kernel.org>
---
v3:
 * Add tag (Jean)
---
 include/linux/dmi.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/include/linux/dmi.h b/include/linux/dmi.h
index 32b2529a73301..2eedf44e68012 100644
--- a/include/linux/dmi.h
+++ b/include/linux/dmi.h
@@ -70,6 +70,10 @@ enum dmi_entry_type {
 	DMI_ENTRY_ADDITIONAL,
 	DMI_ENTRY_ONBOARD_DEV_EXT,
 	DMI_ENTRY_MGMT_CONTROLLER_HOST,
+	DMI_ENTRY_TPM_DEVICE,
+	DMI_ENTRY_PROCESSOR_ADDITIONAL,
+	DMI_ENTRY_FIRMWARE_INVENTORY,
+	DMI_ENTRY_STRING_PROPERTY,
 	DMI_ENTRY_INACTIVE = 126,
 	DMI_ENTRY_END_OF_TABLE = 127,
 };
-- 
2.43.0

[PATCH v3 4/5] firmware: dmi: Add pr_fmt() for dmi_scan.c

[Mario Limonciello (AMD)]

From: Mario Limonciello <mario.limonciello@amd.com>

Several prints inconsistently use DMI: or dmi: or nothing.  To make
it clear which prints come from dmi_scan.c, add a pr_fmt macro.

Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
---
 drivers/firmware/dmi_scan.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/firmware/dmi_scan.c b/drivers/firmware/dmi_scan.c
index 80aded4c778bc..caa09ddf0dfa7 100644
--- a/drivers/firmware/dmi_scan.c
+++ b/drivers/firmware/dmi_scan.c
@@ -1,4 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0-only
+
+#define pr_fmt(fmt) "DMI: " fmt
+
 #include <linux/types.h>
 #include <linux/string.h>
 #include <linux/init.h>
@@ -634,7 +637,7 @@ static int __init dmi_present(const u8 *buf)
 					dmi_ver >> 16, (dmi_ver >> 8) & 0xFF);
 			}
 			dmi_format_ids(dmi_ids_string, sizeof(dmi_ids_string));
-			pr_info("DMI: %s\n", dmi_ids_string);
+			pr_info("%s\n", dmi_ids_string);
 			return 0;
 		}
 	}
@@ -663,7 +666,7 @@ static int __init dmi_smbios3_present(const u8 *buf)
 				dmi_ver >> 16, (dmi_ver >> 8) & 0xFF,
 				dmi_ver & 0xFF);
 			dmi_format_ids(dmi_ids_string, sizeof(dmi_ids_string));
-			pr_info("DMI: %s\n", dmi_ids_string);
+			pr_info("%s\n", dmi_ids_string);
 			return 0;
 		}
 	}
@@ -810,7 +813,7 @@ static int __init dmi_init(void)
 	kobject_del(tables_kobj);
 	kobject_put(tables_kobj);
  err:
-	pr_err("dmi: Firmware registration failed.\n");
+	pr_err("Firmware registration failed.\n");
 
 	return ret;
 }
@@ -831,7 +834,7 @@ void __init dmi_setup(void)
 		return;
 
 	dmi_memdev_walk();
-	pr_info("DMI: Memory slots populated: %d/%d\n",
+	pr_info("Memory slots populated: %d/%d\n",
 		dmi_memdev_populated_nr, dmi_memdev_nr);
 	dump_stack_set_arch_desc("%s", dmi_ids_string);
 }
-- 
2.43.0

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

[Mario Limonciello (AMD)]

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@kernel.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

Re: [PATCH v3 0/5] Parse SMBIOS additional entries

[Yazen Ghannam]

On Sat, Jan 10, 2026 at 07:48:29AM -0600, Mario Limonciello (AMD) wrote:
> The SMBIOS additional entries on AMD Zen4+ systems running an AGESA
> based BIOS contain information about the AGESA version which can be
> useful for matching the software stack when debugging an issue.
> 
> Add support for parsing this from SMBIOS tables and output it into
> the logs at bootup.  Additionally export the information to debugfs
> in case users are interested in any other strings.
> 
> v3:
>  * Drop / merge patches from feedback
>  * Don't save additional strings, only show AGESA string if found
> 
> Mario Limonciello (1):
>   firmware: dmi: Add pr_fmt() for dmi_scan.c
> 
> Mario Limonciello (AMD) (4):
>   firmware: dmi: Correct an indexing error in dmi.h
>   firmware: dmi: Adjust dmi_decode() to use enums
>   firmware: dmi: Add missing DMI entry types
>   firmware: dmi: Read additional information when decoding DMI table
> 

One patch is authored with a different email. Is this intentional?

Not a problem, but wanted to ask just in case.

Thanks,
Yazen

Re: [PATCH v3 0/5] Parse SMBIOS additional entries

[Mario Limonciello (AMD) (kernel.org)]

On 1/16/2026 9:03 AM, Yazen Ghannam wrote:
> On Sat, Jan 10, 2026 at 07:48:29AM -0600, Mario Limonciello (AMD) wrote:
>> The SMBIOS additional entries on AMD Zen4+ systems running an AGESA
>> based BIOS contain information about the AGESA version which can be
>> useful for matching the software stack when debugging an issue.
>>
>> Add support for parsing this from SMBIOS tables and output it into
>> the logs at bootup.  Additionally export the information to debugfs
>> in case users are interested in any other strings.
>>
>> v3:
>>   * Drop / merge patches from feedback
>>   * Don't save additional strings, only show AGESA string if found
>>
>> Mario Limonciello (1):
>>    firmware: dmi: Add pr_fmt() for dmi_scan.c
>>
>> Mario Limonciello (AMD) (4):
>>    firmware: dmi: Correct an indexing error in dmi.h
>>    firmware: dmi: Adjust dmi_decode() to use enums
>>    firmware: dmi: Add missing DMI entry types
>>    firmware: dmi: Read additional information when decoding DMI table
>>
> 
> One patch is authored with a different email. Is this intentional?
> 
> Not a problem, but wanted to ask just in case.
> 

It was an oversight because I worked on two different machines and 
forgot I had git configured differently when I made the commits.

If there are other changes needed for the series I'll fix it in next 
version, otherwise leaving it as is is totally fine for me.

Re: [PATCH v3 3/5] firmware: dmi: Add missing DMI entry types

[Yazen Ghannam]

On Sat, Jan 10, 2026 at 07:48:32AM -0600, Mario Limonciello (AMD) wrote:
> Type 42 through type 46 entry types are missing from the

Should be 43 through 46.

Reviewed-by: Yazen Ghannam <yazen.ghannam@amd.com>

Thanks,
Yazen

> definitions in the dmi_entry_type enum.
> 
> Link: https://www.dmtf.org/sites/default/files/standards/documents/DSP0134_3.7.1.pdf
> Suggested-by: Yazen Ghannam <yazen.ghannam@amd.com>
> Reviewed-by: Jean Delvare <jdelvare@suse.de>
> Signed-off-by: Mario Limonciello (AMD) <superm1@kernel.org>
> ---
> v3:
>  * Add tag (Jean)
> ---
>  include/linux/dmi.h | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/include/linux/dmi.h b/include/linux/dmi.h
> index 32b2529a73301..2eedf44e68012 100644
> --- a/include/linux/dmi.h
> +++ b/include/linux/dmi.h
> @@ -70,6 +70,10 @@ enum dmi_entry_type {
>  	DMI_ENTRY_ADDITIONAL,
>  	DMI_ENTRY_ONBOARD_DEV_EXT,
>  	DMI_ENTRY_MGMT_CONTROLLER_HOST,
> +	DMI_ENTRY_TPM_DEVICE,
> +	DMI_ENTRY_PROCESSOR_ADDITIONAL,
> +	DMI_ENTRY_FIRMWARE_INVENTORY,
> +	DMI_ENTRY_STRING_PROPERTY,
>  	DMI_ENTRY_INACTIVE = 126,
>  	DMI_ENTRY_END_OF_TABLE = 127,
>  };
> -- 
> 2.43.0
> 

Re: [PATCH v3 4/5] firmware: dmi: Add pr_fmt() for dmi_scan.c

[Yazen Ghannam]

On Sat, Jan 10, 2026 at 07:48:33AM -0600, Mario Limonciello (AMD) wrote:
> From: Mario Limonciello <mario.limonciello@amd.com>
> 
> Several prints inconsistently use DMI: or dmi: or nothing.  To make
> it clear which prints come from dmi_scan.c, add a pr_fmt macro.
> 
> Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
> ---
>  drivers/firmware/dmi_scan.c | 11 +++++++----
>  1 file changed, 7 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/firmware/dmi_scan.c b/drivers/firmware/dmi_scan.c
> index 80aded4c778bc..caa09ddf0dfa7 100644
> --- a/drivers/firmware/dmi_scan.c
> +++ b/drivers/firmware/dmi_scan.c
> @@ -1,4 +1,7 @@
>  // SPDX-License-Identifier: GPL-2.0-only
> +
> +#define pr_fmt(fmt) "DMI: " fmt
> +
>  #include <linux/types.h>
>  #include <linux/string.h>
>  #include <linux/init.h>
> @@ -634,7 +637,7 @@ static int __init dmi_present(const u8 *buf)
>  					dmi_ver >> 16, (dmi_ver >> 8) & 0xFF);
>  			}
>  			dmi_format_ids(dmi_ids_string, sizeof(dmi_ids_string));
> -			pr_info("DMI: %s\n", dmi_ids_string);
> +			pr_info("%s\n", dmi_ids_string);
>  			return 0;
>  		}
>  	}
> @@ -663,7 +666,7 @@ static int __init dmi_smbios3_present(const u8 *buf)
>  				dmi_ver >> 16, (dmi_ver >> 8) & 0xFF,
>  				dmi_ver & 0xFF);
>  			dmi_format_ids(dmi_ids_string, sizeof(dmi_ids_string));
> -			pr_info("DMI: %s\n", dmi_ids_string);
> +			pr_info("%s\n", dmi_ids_string);
>  			return 0;
>  		}
>  	}
> @@ -810,7 +813,7 @@ static int __init dmi_init(void)
>  	kobject_del(tables_kobj);
>  	kobject_put(tables_kobj);
>   err:
> -	pr_err("dmi: Firmware registration failed.\n");
> +	pr_err("Firmware registration failed.\n");
>  
>  	return ret;
>  }
> @@ -831,7 +834,7 @@ void __init dmi_setup(void)
>  		return;
>  
>  	dmi_memdev_walk();
> -	pr_info("DMI: Memory slots populated: %d/%d\n",
> +	pr_info("Memory slots populated: %d/%d\n",
>  		dmi_memdev_populated_nr, dmi_memdev_nr);
>  	dump_stack_set_arch_desc("%s", dmi_ids_string);
>  }
> -- 
> 

What about dropping "DMI" from this one too?
	pr_info("DMI not present or invalid.\n");

Thanks,
Yazen

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

[Yazen Ghannam]

On Sat, Jan 10, 2026 at 07:48:34AM -0600, Mario Limonciello (AMD) wrote:
> 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.
> 

Should have imperative voice.

> Signed-off-by: Mario Limonciello (AMD) <superm1@kernel.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;

This is wrong. The "entries" are not u8. They are structs with this
format:
	Table 119 – Additional Information Entry format

struct dmi_additional_info_entry {
	u8 length;
	u16 handle;
	u8 offset;
	u8 string
	/* Variable length "Value" */
} __packed; 

ACPI tables do this a lot. So there are examples of iterating over
variable length entries.

Thanks,
Yazen

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

[Yazen Ghannam]

On Fri, Jan 16, 2026 at 04:30:32PM -0500, Yazen Ghannam wrote:
> On Sat, Jan 10, 2026 at 07:48:34AM -0600, Mario Limonciello (AMD) wrote:
> 

[...]

> ACPI tables do this a lot. So there are examples of iterating over
> variable length entries.

Here's another implementation. What do you think?

Thanks,
Yazen


From c76f27e5d55570bb25bcefc3365fb3a1852bcad3 Mon Sep 17 00:00:00 2001
From: Yazen Ghannam <yazen.ghannam@amd.com>
Date: Mon, 19 Jan 2026 18:33:09 +0000
Subject: [PATCH] x86/CPU/AMD: Print AGESA string from DMI additional
 information entry

Type 40 entries (Additional Information) are summarized in section 7.41
as part of the SMBIOS specification.  Generally, these entries aren't
interesting to save.

However on some AMD Zen systems, the AGESA version is stored here. This
is useful to save to the kernel message logs for debugging. It can be
used to cross-reference issues.

Implement an iterator for the Additional Information entries. Use this
to find and print the AGESA string. Do so in AMD code, since the use
case is AMD-specific.

Originally-by: "Mario Limonciello (AMD)" <superm1@kernel.org>
Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
---
 arch/x86/kernel/cpu/amd.c   | 53 +++++++++++++++++++++++++++++++++++++
 drivers/firmware/dmi_scan.c |  3 ++-
 include/linux/dmi.h         | 18 +++++++++++++
 3 files changed, 73 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index bc94ff1e250a..aa04a27aeb10 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0-only
 #include <linux/export.h>
 #include <linux/bitops.h>
+#include <linux/dmi.h>
 #include <linux/elf.h>
 #include <linux/mm.h>
 #include <linux/kvm_types.h>
@@ -1404,3 +1405,55 @@ static __init int print_s5_reset_status_mmio(void)
 	return 0;
 }
 late_initcall(print_s5_reset_status_mmio);
+
+static void __init amd_dmi_scan_additional(const struct dmi_header *d, void *p)
+{
+	struct dmi_a_info *info = (struct dmi_a_info *)d;
+	void *next, *end;
+
+	/*
+	 * DMI Additional Info table has a 'count' field. But it's not very
+	 * helpful since the entries are variable length. So don't use it.
+	 */
+	if (info->header.type != DMI_ENTRY_ADDITIONAL ||
+	    info->header.length < DMI_A_INFO_MIN_SIZE)
+		return;
+
+	/*
+	 * Get the first entry.
+	 * The minimum table size guarantees at least one entry is present.
+	 */
+	next = (void *)(info + 1);
+	end  = (void *)info + info->header.length;
+
+	do {
+		struct dmi_a_info_entry *entry;
+		const char *string_ptr;
+
+		entry = (struct dmi_a_info_entry *)next;
+
+		/*
+		 * Not much can be done to validate data. At least the entry
+		 * length shouldn't be 0.
+		 */
+		if (!entry->length)
+			return;
+
+		string_ptr = dmi_string_nosave(&info->header, entry->str_num);
+
+		/* Only one AGESA string is expected. */
+		if (!strncmp(string_ptr, "AGESA", 5)) {
+			pr_info("%s\n", string_ptr);
+			break;
+		}
+
+		next += entry->length;
+	} while (end - next >= DMI_A_INFO_ENT_MIN_SIZE);
+}
+
+static __init int print_dmi_agesa(void)
+{
+	dmi_walk(amd_dmi_scan_additional, NULL);
+	return 0;
+}
+late_initcall(print_dmi_agesa);
diff --git a/drivers/firmware/dmi_scan.c b/drivers/firmware/dmi_scan.c
index caa09ddf0dfa..8b196992618d 100644
--- a/drivers/firmware/dmi_scan.c
+++ b/drivers/firmware/dmi_scan.c
@@ -47,7 +47,7 @@ static struct dmi_memdev_info {
 static int dmi_memdev_nr;
 static int dmi_memdev_populated_nr __initdata;
 
-static const char * __init dmi_string_nosave(const struct dmi_header *dm, u8 s)
+const char *dmi_string_nosave(const struct dmi_header *dm, u8 s)
 {
 	const u8 *bp = ((u8 *) dm) + dm->length;
 	const u8 *nsp;
@@ -66,6 +66,7 @@ static const char * __init dmi_string_nosave(const struct dmi_header *dm, u8 s)
 
 	return dmi_empty_string;
 }
+EXPORT_SYMBOL_GPL(dmi_string_nosave);
 
 static const char * __init dmi_string(const struct dmi_header *dm, u8 s)
 {
diff --git a/include/linux/dmi.h b/include/linux/dmi.h
index 2eedf44e6801..48691d589b88 100644
--- a/include/linux/dmi.h
+++ b/include/linux/dmi.h
@@ -91,6 +91,21 @@ struct dmi_device {
 	void *device_data;	/* Type specific data */
 };
 
+#define DMI_A_INFO_ENT_MIN_SIZE 0x6
+struct dmi_a_info_entry {
+	u8 length;
+	u16 handle;
+	u8 offset;
+	u8 str_num;
+	u8 value[];
+} __packed;
+
+#define DMI_A_INFO_MIN_SIZE	0xB
+struct dmi_a_info {
+	struct dmi_header header;
+	u8 count;
+} __packed;
+
 #ifdef CONFIG_DMI
 
 struct dmi_dev_onboard {
@@ -120,6 +135,7 @@ extern void dmi_memdev_name(u16 handle, const char **bank, const char **device);
 extern u64 dmi_memdev_size(u16 handle);
 extern u8 dmi_memdev_type(u16 handle);
 extern u16 dmi_memdev_handle(int slot);
+const char *dmi_string_nosave(const struct dmi_header *dm, u8 s);
 
 #else
 
@@ -153,6 +169,8 @@ static inline u8 dmi_memdev_type(u16 handle) { return 0x0; }
 static inline u16 dmi_memdev_handle(int slot) { return 0xffff; }
 static inline const struct dmi_system_id *
 	dmi_first_match(const struct dmi_system_id *list) { return NULL; }
+static inline const char *
+	dmi_string_nosave(const struct dmi_header *dm, u8 s) { return NULL; }
 
 #endif
 
-- 
2.52.0

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

[Mario Limonciello]

On 1/20/26 3:45 PM, Yazen Ghannam wrote:
> On Fri, Jan 16, 2026 at 04:30:32PM -0500, Yazen Ghannam wrote:
>> On Sat, Jan 10, 2026 at 07:48:34AM -0600, Mario Limonciello (AMD) wrote:
>>
> 
> [...]
> 
>> ACPI tables do this a lot. So there are examples of iterating over
>> variable length entries.
> 
> Here's another implementation. What do you think?

Oh you beat me to it, been busy this week.

I do like that we can localize the printing code to amd.c.  I'll test it 
and let you know if it works.

If it does; I'll roll it into the series.

> 
> Thanks,
> Yazen
> 
> 
>  From c76f27e5d55570bb25bcefc3365fb3a1852bcad3 Mon Sep 17 00:00:00 2001
> From: Yazen Ghannam <yazen.ghannam@amd.com>
> Date: Mon, 19 Jan 2026 18:33:09 +0000
> Subject: [PATCH] x86/CPU/AMD: Print AGESA string from DMI additional
>   information entry
> 
> Type 40 entries (Additional Information) are summarized in section 7.41
> as part of the SMBIOS specification.  Generally, these entries aren't
> interesting to save.
> 
> However on some AMD Zen systems, the AGESA version is stored here. This
> is useful to save to the kernel message logs for debugging. It can be
> used to cross-reference issues.
> 
> Implement an iterator for the Additional Information entries. Use this
> to find and print the AGESA string. Do so in AMD code, since the use
> case is AMD-specific.
> 
> Originally-by: "Mario Limonciello (AMD)" <superm1@kernel.org>
> Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
> ---
>   arch/x86/kernel/cpu/amd.c   | 53 +++++++++++++++++++++++++++++++++++++
>   drivers/firmware/dmi_scan.c |  3 ++-
>   include/linux/dmi.h         | 18 +++++++++++++
>   3 files changed, 73 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
> index bc94ff1e250a..aa04a27aeb10 100644
> --- a/arch/x86/kernel/cpu/amd.c
> +++ b/arch/x86/kernel/cpu/amd.c
> @@ -1,6 +1,7 @@
>   // SPDX-License-Identifier: GPL-2.0-only
>   #include <linux/export.h>
>   #include <linux/bitops.h>
> +#include <linux/dmi.h>
>   #include <linux/elf.h>
>   #include <linux/mm.h>
>   #include <linux/kvm_types.h>
> @@ -1404,3 +1405,55 @@ static __init int print_s5_reset_status_mmio(void)
>   	return 0;
>   }
>   late_initcall(print_s5_reset_status_mmio);
> +
> +static void __init amd_dmi_scan_additional(const struct dmi_header *d, void *p)
> +{
> +	struct dmi_a_info *info = (struct dmi_a_info *)d;
> +	void *next, *end;
> +
> +	/*
> +	 * DMI Additional Info table has a 'count' field. But it's not very
> +	 * helpful since the entries are variable length. So don't use it.
> +	 */
> +	if (info->header.type != DMI_ENTRY_ADDITIONAL ||
> +	    info->header.length < DMI_A_INFO_MIN_SIZE)
> +		return;
> +
> +	/*
> +	 * Get the first entry.
> +	 * The minimum table size guarantees at least one entry is present.
> +	 */
> +	next = (void *)(info + 1);
> +	end  = (void *)info + info->header.length;
> +
> +	do {
> +		struct dmi_a_info_entry *entry;
> +		const char *string_ptr;
> +
> +		entry = (struct dmi_a_info_entry *)next;
> +
> +		/*
> +		 * Not much can be done to validate data. At least the entry
> +		 * length shouldn't be 0.
> +		 */
> +		if (!entry->length)
> +			return;
> +
> +		string_ptr = dmi_string_nosave(&info->header, entry->str_num);
> +
> +		/* Only one AGESA string is expected. */
> +		if (!strncmp(string_ptr, "AGESA", 5)) {
> +			pr_info("%s\n", string_ptr);
> +			break;
> +		}
> +
> +		next += entry->length;
> +	} while (end - next >= DMI_A_INFO_ENT_MIN_SIZE);
> +}
> +
> +static __init int print_dmi_agesa(void)
> +{
> +	dmi_walk(amd_dmi_scan_additional, NULL);
> +	return 0;
> +}
> +late_initcall(print_dmi_agesa);
> diff --git a/drivers/firmware/dmi_scan.c b/drivers/firmware/dmi_scan.c
> index caa09ddf0dfa..8b196992618d 100644
> --- a/drivers/firmware/dmi_scan.c
> +++ b/drivers/firmware/dmi_scan.c
> @@ -47,7 +47,7 @@ static struct dmi_memdev_info {
>   static int dmi_memdev_nr;
>   static int dmi_memdev_populated_nr __initdata;
>   
> -static const char * __init dmi_string_nosave(const struct dmi_header *dm, u8 s)
> +const char *dmi_string_nosave(const struct dmi_header *dm, u8 s)
>   {
>   	const u8 *bp = ((u8 *) dm) + dm->length;
>   	const u8 *nsp;
> @@ -66,6 +66,7 @@ static const char * __init dmi_string_nosave(const struct dmi_header *dm, u8 s)
>   
>   	return dmi_empty_string;
>   }
> +EXPORT_SYMBOL_GPL(dmi_string_nosave);
>   
>   static const char * __init dmi_string(const struct dmi_header *dm, u8 s)
>   {
> diff --git a/include/linux/dmi.h b/include/linux/dmi.h
> index 2eedf44e6801..48691d589b88 100644
> --- a/include/linux/dmi.h
> +++ b/include/linux/dmi.h
> @@ -91,6 +91,21 @@ struct dmi_device {
>   	void *device_data;	/* Type specific data */
>   };
>   
> +#define DMI_A_INFO_ENT_MIN_SIZE 0x6
> +struct dmi_a_info_entry {
> +	u8 length;
> +	u16 handle;
> +	u8 offset;
> +	u8 str_num;
> +	u8 value[];
> +} __packed;
> +
> +#define DMI_A_INFO_MIN_SIZE	0xB
> +struct dmi_a_info {
> +	struct dmi_header header;
> +	u8 count;
> +} __packed;
> +
>   #ifdef CONFIG_DMI
>   
>   struct dmi_dev_onboard {
> @@ -120,6 +135,7 @@ extern void dmi_memdev_name(u16 handle, const char **bank, const char **device);
>   extern u64 dmi_memdev_size(u16 handle);
>   extern u8 dmi_memdev_type(u16 handle);
>   extern u16 dmi_memdev_handle(int slot);
> +const char *dmi_string_nosave(const struct dmi_header *dm, u8 s);
>   
>   #else
>   
> @@ -153,6 +169,8 @@ static inline u8 dmi_memdev_type(u16 handle) { return 0x0; }
>   static inline u16 dmi_memdev_handle(int slot) { return 0xffff; }
>   static inline const struct dmi_system_id *
>   	dmi_first_match(const struct dmi_system_id *list) { return NULL; }
> +static inline const char *
> +	dmi_string_nosave(const struct dmi_header *dm, u8 s) { return NULL; }
>   
>   #endif
>   

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

[Yazen Ghannam]

On Tue, Jan 20, 2026 at 03:55:54PM -0600, Mario Limonciello wrote:
> On 1/20/26 3:45 PM, Yazen Ghannam wrote:
> > On Fri, Jan 16, 2026 at 04:30:32PM -0500, Yazen Ghannam wrote:
> > > On Sat, Jan 10, 2026 at 07:48:34AM -0600, Mario Limonciello (AMD) wrote:
> > > 
> > 
> > [...]
> > 
> > > ACPI tables do this a lot. So there are examples of iterating over
> > > variable length entries.
> > 
> > Here's another implementation. What do you think?
> 
> Oh you beat me to it, been busy this week.
> 
> I do like that we can localize the printing code to amd.c.  I'll test it and
> let you know if it works.
> 
> If it does; I'll roll it into the series.
> 

Good deal, thanks!

[...]

> > +
> > +		string_ptr = dmi_string_nosave(&info->header, entry->str_num);
> > +
> > +		/* Only one AGESA string is expected. */
> > +		if (!strncmp(string_ptr, "AGESA", 5)) {
> > +			pr_info("%s\n", string_ptr);
> > +			break;
> > +		}
> > +

[...]

> > +static inline const char *
> > +	dmi_string_nosave(const struct dmi_header *dm, u8 s) { return NULL; }

Found a bug. :/

The default return value should be "dmi_empty_string".

Thanks,
Yazen