[PATCH v2] cdev: maintain partition index in struct cdev

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

For use by the EFI loader, we will need to know a partition's number
within the partition table on disk, so have the devfs-core keep track
of that.

Mere iteration over the cdev list doesn't work for thus purpose as there
may be invalid PTEs, which cause e.g. the first on-disk partition to
have a higher number.

See 9dfffaf2ef47 ("partitions: efi: Continue partition enumeration on
invalid pte") for more info. A real world example is the current
debian-13-nocloud-arm64.raw image, which has two partitions:
0 and 14 (or 1 and 15 in barebox).

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
---
v1 -> v2:
  - record actual partition number from the table.
    I compared against EDK-II and Linux and both take the actual
    number, which may not be either the number in our cdev list
    or the location on disk.
---
 common/partitions.c | 1 +
 include/driver.h    | 3 +++
 2 files changed, 4 insertions(+)

diff --git a/common/partitions.c b/common/partitions.c
index 1a4e046c5f55..40f4c629e1ac 100644
--- a/common/partitions.c
+++ b/common/partitions.c
@@ -52,6 +52,7 @@ static int register_one_partition(struct block_device *blk, struct partition *pa
 		goto out;
 	}
 
+	cdev->partition_table_index = part->num;
 	cdev->flags |= DEVFS_PARTITION_FROM_TABLE | part->flags;
 	cdev->typeflags |= part->typeflags;
 	cdev->typeuuid = part->typeuuid;
diff --git a/include/driver.h b/include/driver.h
index 14d1731fd976..01e16e7a73ab 100644
--- a/include/driver.h
+++ b/include/driver.h
@@ -436,6 +436,9 @@ struct cdev {
 	loff_t size;
 	unsigned int flags;
 	u16 typeflags; /* GPT type-specific attributes */
+	s8 partition_table_index;    /* For GPT/MBR-formatted disks only:
+				      * 1-based index of partition on disk
+				      */
 	int open;
 	struct mtd_info *mtd;
 	struct list_head aliases;
-- 
2.47.3