Re: [PATCH 1/3] block: sed-opal: add ioctl for done-mark of shadow mbr

From: David Kozub
Date: Wed May 01 2019 - 06:37:23 EST

On Wed, 1 May 2019, David Kozub wrote:

@@ -104,6 +109,12 @@ struct opal_mbr_data {
__u8 __align[7];

+struct opal_mbr_done {
+ struct opal_key key;
+ __u8 done_flag;
+ __u8 __align[7];

While I just copied opal_mbr_data here, I wonder what is the point of __align in these structs. By itself it just pads the structure to have a size that is a multiple of 8. Is this to make sure that anything that lies past the structure is 8-bytes aligned (assuming the start is 8-bytes aligned too), perhaps for 32bit userspace with 64bit kernel?

And if it's this, is it needed for these IOCTL structs? (I can see it being useful for struct opal_key.)

Best regards,