[PATCH v2 5/7] disk: part_dos: Refactor to allow retrieving raw MBR partition data

[Javier Martinez Canillas]

Refactor the part_get_info_extended() helper function (which already
recursively traverses DOS partitions) to optionally return the raw MBR
partition structure (dos_partition_t).

This allows other subsystems, such as EFI, to retrieve the partition
details in the legacy MBR format.

Signed-off-by: Javier Martinez Canillas <javierm at redhat.com>
---

(no changes since v1)

 disk/part_dos.c | 66 ++++++++++++++++++++++++++++++-------------------
 include/part.h  | 14 +++++++++++
 2 files changed, 55 insertions(+), 25 deletions(-)

diff --git a/disk/part_dos.c b/disk/part_dos.c
index a69ad8962106..4e1d01b2f21e 100644
--- a/disk/part_dos.c
+++ b/disk/part_dos.c
@@ -204,7 +204,8 @@ static void print_partition_extended(struct blk_desc *desc,
  * @relative:		Relative offset for the partition
  * @part_num:		Current partition number
  * @which_part:		Target partition number
- * @info:		Returns a pointer to the partition info
+ * @info:		Returns partition information (optional)
+ * @mbr:		Returns MBR partition entry (optional)
  * @disksig:		Disk signature
  *
  * Return:		0 on success, negative on error
@@ -212,7 +213,9 @@ static void print_partition_extended(struct blk_desc *desc,
 static int part_get_info_extended(struct blk_desc *desc,
 				  lbaint_t ext_part_sector, lbaint_t relative,
 				  int part_num, int which_part,
-				  struct disk_partition *info, uint disksig)
+				  struct disk_partition *info,
+				  dos_partition_t *mbr,
+				  uint disksig)
 {
 	ALLOC_CACHE_ALIGN_BUFFER(unsigned char, buffer, desc->blksz);
 	struct disk_partition wdinfo = { 0 };
@@ -243,9 +246,11 @@ static int part_get_info_extended(struct blk_desc *desc,
 	if (CONFIG_IS_ENABLED(PARTITION_UUIDS) && !ext_part_sector)
 		disksig = get_unaligned_le32(&buffer[DOS_PART_DISKSIG_OFFSET]);
 
-	ret = part_get_info_whole_disk(desc, &wdinfo);
-	if (ret)
-		return ret;
+	if (info) {
+		ret = part_get_info_whole_disk(desc, &wdinfo);
+		if (ret)
+			return ret;
+	}
 
 	/* Print all primary/logical partitions */
 	pt = (dos_partition_t *) (buffer + DOS_PART_TBL_OFFSET);
@@ -258,25 +263,29 @@ static int part_get_info_extended(struct blk_desc *desc,
 		    (pt->sys_ind != 0) &&
 		    (part_num == which_part) &&
 		    (ext_part_sector == 0 || is_extended(pt->sys_ind) == 0)) {
-			if (wdinfo.blksz > DOS_PART_DEFAULT_SECTOR)
-				info->blksz = wdinfo.blksz;
-			else
-				info->blksz = DOS_PART_DEFAULT_SECTOR;
-			info->start = (lbaint_t)(ext_part_sector +
-					get_unaligned_le32(&pt->start_sect));
-			info->size  = (lbaint_t)get_unaligned_le32(&pt->nr_sects);
-			part_set_generic_name(desc, part_num,
-					      (char *)info->name);
-			/* sprintf(info->type, "%d, pt->sys_ind); */
-			strcpy((char *)info->type, "U-Boot");
-			info->bootable = get_bootable(pt);
-			if (CONFIG_IS_ENABLED(PARTITION_UUIDS)) {
-				char str[12];
-
-				sprintf(str, "%08x-%02x", disksig, part_num);
-				disk_partition_set_uuid(info, str);
+			if (info) {
+				if (wdinfo.blksz > DOS_PART_DEFAULT_SECTOR)
+					info->blksz = wdinfo.blksz;
+				else
+					info->blksz = DOS_PART_DEFAULT_SECTOR;
+				info->start = (lbaint_t)(ext_part_sector +
+							 get_unaligned_le32(&pt->start_sect));
+				info->size  = (lbaint_t)get_unaligned_le32(&pt->nr_sects);
+				part_set_generic_name(desc, part_num,
+						      (char *)info->name);
+				/* sprintf(info->type, "%d, pt->sys_ind); */
+				strcpy((char *)info->type, "U-Boot");
+				info->bootable = get_bootable(pt);
+				if (CONFIG_IS_ENABLED(PARTITION_UUIDS)) {
+					char str[12];
+
+					sprintf(str, "%08x-%02x", disksig, part_num);
+					disk_partition_set_uuid(info, str);
+				}
+				info->sys_ind = pt->sys_ind;
 			}
-			info->sys_ind = pt->sys_ind;
+			if (mbr)
+				memcpy(mbr, pt, sizeof(*mbr));
 			return 0;
 		}
 
@@ -296,7 +305,8 @@ static int part_get_info_extended(struct blk_desc *desc,
 
 			return part_get_info_extended(desc, lba_start,
 				 ext_part_sector == 0 ? lba_start : relative,
-				 part_num, which_part, info, disksig);
+						      part_num, which_part, info,
+						      mbr, disksig);
 		}
 	}
 
@@ -328,7 +338,13 @@ static void __maybe_unused part_print_dos(struct blk_desc *desc)
 static int __maybe_unused part_get_info_dos(struct blk_desc *desc, int part,
 					    struct disk_partition *info)
 {
-	return part_get_info_extended(desc, 0, 0, 1, part, info, 0);
+	return part_get_info_extended(desc, 0, 0, 1, part, info, NULL, 0);
+}
+
+int __maybe_unused part_get_mbr(struct blk_desc *desc, int part,
+				dos_partition_t *mbr)
+{
+	return part_get_info_extended(desc, 0, 0, 1, part, NULL, mbr, 0);
 }
 
 int is_valid_dos_buf(void *buf)
diff --git a/include/part.h b/include/part.h
index daebbbc2e68f..aed089d00f64 100644
--- a/include/part.h
+++ b/include/part.h
@@ -704,6 +704,20 @@ int write_mbr_partitions(struct blk_desc *dev,
 int layout_mbr_partitions(struct disk_partition *p, int count,
 			  lbaint_t total_sectors);
 
+/**
+ * part_get_mbr() - get the MBR partition record of a partition
+ *
+ * This function reads the MBR partition record for a given block
+ * device and partition number.
+ *
+ * @desc:	block device descriptor
+ * @part:	partition number for which to return the partition record
+ * @mbr:	MBR partition record
+ *
+ * Return:	0 on success, otherwise error
+ */
+int part_get_mbr(struct blk_desc *desc, int part, dos_partition_t *mbr);
+
 #endif
 
 #if CONFIG_IS_ENABLED(PARTITIONS)
-- 
2.53.0