[smbios] Allow access to multiple instances of SMBIOS structures

Extend the syntax for numerical SMBIOS settings from

  smbios/<type>.<offset>.<length>

to

  smbios/[<instance>.]<type>.<offset>.<length>

Where SMBIOS provides multiple structures with the same <type>, this
extended syntax allows for access to structures other than the first.
If <instance> is omitted then it will default to zero, giving access
to the first instance (and so matching existing behaviour).

The 16-bit SMBIOS handle (which is an alternative way to disambiguate
multiple instances of the same type of structure) can be accessed, if
required, using

  smbios/<instance>.<type>.2.2:uint16

Signed-off-by: Michael Brown <mcb30@ipxe.org>

1 files changed, 4 insertions, 2 deletions

diff --git a/src/interface/smbios/smbios.c b/src/interface/smbios/smbios.c
index 2adaa53d9..90907e18e 100644
--- a/src/interface/smbios/smbios.c
+++ b/src/interface/smbios/smbios.c
@@ -59,10 +59,11 @@ static size_t find_strings_terminator ( size_t offset ) {
  * Find specific structure type within SMBIOS
  *
  * @v type		Structure type to search for
+ * @v instance		Instance of this type of structure
  * @v structure		SMBIOS structure descriptor to fill in
  * @ret rc		Return status code
  */
-int find_smbios_structure ( unsigned int type,
+int find_smbios_structure ( unsigned int type, unsigned int instance,
 			    struct smbios_structure *structure ) {
 	unsigned int count = 0;
 	size_t offset = 0;
@@ -105,7 +106,8 @@ int find_smbios_structure ( unsigned int type,
 		      structure->header.len, structure->strings_len );
 
 		/* If this is the structure we want, return */
-		if ( structure->header.type == type ) {
+		if ( ( structure->header.type == type ) &&
+		     ( instance-- == 0 ) ) {
 			structure->offset = offset;
 			return 0;
 		}