A simple test infrastructure -- idea stolen from Gaurav.

src/platform/vboot_reference/cgptlib/cgpt.h

Index: src/platform/vboot_reference/cgptlib/cgpt.h
diff --git a/src/platform/vboot_reference/cgptlib/cgpt.h b/src/platform/vboot_reference/cgptlib/cgpt.h
index acc1ec9e66c06f9e18bc59fa2698e13d0d7e62bb..c9cd04ddb9c9d93eed0e523af2830869ec7d7858 100644
--- a/src/platform/vboot_reference/cgptlib/cgpt.h
+++ b/src/platform/vboot_reference/cgptlib/cgpt.h
@@ -9,10 +9,11 @@
 #include <stdint.h>
 
 enum {
-        GPT_ERROR_INVALID_HEADERS = 1,
-        GPT_ERROR_INVALID_ENTRIES,
-        GPT_ERROR_INVALID_SECTOR_SIZE,
-        GPT_ERROR_INVALID_SECTOR_NUMBER,
+  GPT_ERROR_NO_VALID_KERNEL = 1,
+  GPT_ERROR_INVALID_HEADERS,
+  GPT_ERROR_INVALID_ENTRIES,
+  GPT_ERROR_INVALID_SECTOR_SIZE,
+  GPT_ERROR_INVALID_SECTOR_NUMBER,
 };
 
 #define GPT_MODIFIED_HEADER1 0x01
@@ -28,27 +29,27 @@ enum {
    * invalid. */
 
 struct GPTData {
-        /* Fill in the following fields before calling GPTInit() */
-        uint8_t *header1;       /* GPT primary header, from sector 1 of disk
-                                 *   (size: 512 bytes) */
-	uint8_t *header2;       /* GPT secondary header, from last sector of
-                                 *   disk (size: 512 bytes) */
-	uint8_t *entries1;      /* primary GPT table, follows primary header
-                                 *   (size: 16 KB) */
-	uint8_t *entries2;      /* secondary GPT table, precedes secondary
-                                 *   header (size: 16 KB) */
-	uint32_t sector_bytes;  /* Size of a LBA sector, in bytes */
-	uint64_t drive_sectors; /* Size of drive in LBA sectors, in sectors */
+  /* Fill in the following fields before calling GPTInit() */
+  uint8_t *header1;       /* GPT primary header, from sector 1 of disk
+                           *   (size: 512 bytes) */
+  uint8_t *header2;       /* GPT secondary header, from last sector of
+                           *   disk (size: 512 bytes) */
+  uint8_t *entries1;      /* primary GPT table, follows primary header
+                           *   (size: 16 KB) */
+  uint8_t *entries2;      /* secondary GPT table, precedes secondary
+                           *   header (size: 16 KB) */
+  uint32_t sector_bytes;  /* Size of a LBA sector, in bytes */
+  uint64_t drive_sectors; /* Size of drive in LBA sectors, in sectors */
 
-	/* Outputs */
-	uint8_t modified;       /* Which inputs have been modified?
-	                         * 0x01 = header1
-	                         * 0x02 = header2
-	                         * 0x04 = table1
-	                         * 0x08 = table2  */
+  /* Outputs */
+  uint8_t modified;       /* Which inputs have been modified?
+                           * 0x01 = header1
+                           * 0x02 = header2
+                           * 0x04 = table1
+                           * 0x08 = table2  */
 
-        /* Internal state */
-        uint8_t current_kernel; // the current kernel index
+  /* Internal state */
+  uint8_t current_kernel; // the current kernel index
 };
 typedef struct GPTData GPTData_t;
 
@@ -74,7 +75,8 @@ int GPTNextKernelEntry(GPTData_t *gpt, uint64_t *start_sector, uint64_t *size);
  * for the start of the kernel partition, and the size parameter contains the
  * size of the kernel partition in LBA sectors.
  *
- * Returns 0 if successful, 1 if error or no more sectors.  */
+ * Returns 0 if successful, else
+ *   GPT_ERROR_NO_VALID_KERNEL, no avaliable kernel, enters recovery mode */
 
 int GPTUpdateKernelEntry(GPTData_t *gpt, uint32_t update_type);
 /* Updates the kernel entry with the specified index, using the specified type
@@ -85,4 +87,4 @@ int GPTUpdateKernelEntry(GPTData_t *gpt, uint32_t update_type);
  *
  * Returns 0 if successful, 1 if error. */
 
-#endif  // VBOOT_REFERENCE_CGPT_H_
+#endif  /* VBOOT_REFERENCE_CGPT_H_ */