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[efi] Add efi_path_guid() utility function

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EFI provides no API for determining the partition GUID (if any) for a
specified device handle.  The partition GUID appears to be exposed
only as part of the device path.

Add efi_path_guid() to extract the partition GUID (if any) from a
device path.

Signed-off-by: Michael Brown <mcb30@ipxe.org>
This commit is contained in:
Michael Brown
2024-03-05 20:00:15 +00:00
parent 636ccb4ca5
commit c4471e3408
3 changed files with 46 additions and 0 deletions
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43
src/interface/efi/efi_path.c
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@@ -22,9 +22,11 @@ FILE_LICENCE ( GPL2_OR_LATER );
#include <stdlib.h>
#include <stdarg.h>
#include <string.h>
#include <errno.h>
#include <byteswap.h>
#include <ipxe/netdevice.h>
#include <ipxe/vlan.h>
#include <ipxe/uuid.h>
#include <ipxe/tcpip.h>
#include <ipxe/uri.h>
#include <ipxe/iscsi.h>
@@ -132,6 +134,47 @@ unsigned int efi_path_vlan ( EFI_DEVICE_PATH_PROTOCOL *path ) {
return 0;
}
/**
* Get partition GUID from device path
*
* @v path Device path
* @v guid Partition GUID to fill in
* @ret rc Return status code
*/
int efi_path_guid ( EFI_DEVICE_PATH_PROTOCOL *path, union uuid *guid ) {
EFI_DEVICE_PATH_PROTOCOL *next;
HARDDRIVE_DEVICE_PATH *hd;
int rc;
/* Search for most specific partition device path */
rc = -ENOENT;
for ( ; ( next = efi_path_next ( path ) ) ; path = next ) {
/* Skip non-harddrive device paths */
if ( path->Type != MEDIA_DEVICE_PATH )
continue;
if ( path->SubType != MEDIA_HARDDRIVE_DP )
continue;
/* Skip non-GUID signatures */
hd = container_of ( path, HARDDRIVE_DEVICE_PATH, Header );
if ( hd->SignatureType != SIGNATURE_TYPE_GUID )
continue;
/* Extract GUID */
memcpy ( guid, hd->Signature, sizeof ( *guid ) );
uuid_mangle ( guid );
/* Record success, but continue searching in case
* there exists a more specific GUID (e.g. a partition
* GUID rather than a disk GUID).
*/
rc = 0;
}
return rc;
}
/**
* Concatenate EFI device paths
*