drivers: partition: Add simple MBR partition entries support

This is to add simple MBR partition entry support. This will read all four
MBR partition into the partition list, and the partition type will be saved
in the list.name[0] entry.
Signed-off-by: Loh Tien Hock <tien.hock.loh@intel.com>

drivers/partition/partition.c

@@ -105,6 +105,57 @@ static int load_gpt_header(uintptr_t image_handle)
 	return 0;
 }
 
+static int load_mbr_entry(uintptr_t image_handle, mbr_entry_t *mbr_entry,
+			int part_number)
+{
+	size_t bytes_read;
+	uintptr_t offset;
+	int result;
+
+	assert(mbr_entry != NULL);
+	/* MBR partition table is in LBA0. */
+	result = io_seek(image_handle, IO_SEEK_SET, MBR_OFFSET);
+	if (result != 0) {
+		WARN("Failed to seek (%i)\n", result);
+		return result;
+	}
+	result = io_read(image_handle, (uintptr_t)&mbr_sector,
+			 PARTITION_BLOCK_SIZE, &bytes_read);
+	if (result != 0) {
+		WARN("Failed to read data (%i)\n", result);
+		return result;
+	}
+
+	/* Check MBR boot signature. */
+	if ((mbr_sector[PARTITION_BLOCK_SIZE - 2] != MBR_SIGNATURE_FIRST) ||
+	    (mbr_sector[PARTITION_BLOCK_SIZE - 1] != MBR_SIGNATURE_SECOND)) {
+		return -ENOENT;
+	}
+	offset = (uintptr_t)&mbr_sector +
+		MBR_PRIMARY_ENTRY_OFFSET +
+		MBR_PRIMARY_ENTRY_SIZE * part_number;
+	memcpy(mbr_entry, (void *)offset, sizeof(mbr_entry_t));
+
+	return 0;
+}
+
+static int load_mbr_entries(uintptr_t image_handle)
+{
+	mbr_entry_t mbr_entry;
+	int i;
+
+	list.entry_count = MBR_PRIMARY_ENTRY_NUMBER;
+
+	for (i = 0; i < list.entry_count; i++) {
+		load_mbr_entry(image_handle, &mbr_entry, i);
+		list.list[i].start = mbr_entry.first_lba * 512;
+		list.list[i].length = mbr_entry.sector_nums * 512;
+		list.list[i].name[0] = mbr_entry.type;
+	}
+
+	return 0;
+}
+
 static int load_gpt_entry(uintptr_t image_handle, gpt_entry_t *entry)
 {
 	size_t bytes_read;
@@ -175,11 +226,9 @@ int load_partition_table(unsigned int image_id)
 		assert(result == 0);
 		result = verify_partition_gpt(image_handle);
 	} else {
-		/* MBR type isn't supported yet. */
-		result = -EINVAL;
-		goto exit;
+		result = load_mbr_entries(image_handle);
 	}
-exit:
+
 	io_close(image_handle);
 	return result;
 }