virtio_blk devices on linux and FL_CD ?

[Dan Mack]

Anyone know why sda doesn't have the FL_CD bit set but vda (virtio_blk) devices do ?

I just came across this when working through a disk enumerator for an
OS install when running my tests under bhyve and was curious.

The linux genhd.h file isn't super clear as to what GEN_FL_CD means
but I think it is CDROM ???

  #define GENHD_FL_REMOVABLE                      1
  /* 2 is unused */
  #define GENHD_FL_MEDIA_CHANGE_NOTIFY            4
  #define GENHD_FL_CD                             8
  #define GENHD_FL_UP                             16
  #define GENHD_FL_SUPPRESS_PARTITION_INFO        32
  #define GENHD_FL_EXT_DEVT                       64 /* allow extended devt */
  #define GENHD_FL_NATIVE_CAPACITY                128
  #define GENHD_FL_BLOCK_EVENTS_ON_EXCL_WRITE     256
  #define GENHD_FL_NO_PART_SCAN                   512

or does it mean character device ?

On a bhyve Linux system I see this for example:

[root at cent ~]# ./diskcapability.bash
sr0  (cap == 119)
  |  REMOVABLE
  |  MEDIA_CHANGE_NOTIFY
  |  UP
  |  SUPPRESS_PARTITION_INFO
  |  EXT_DEVT
vda  (cap == 10)
  |  CD

I don't think this has anything to do with bhyve becuase the same
thing happens on a digital ocean coreos system.

The linux header file says '2' is unused but it appears to be set, no?  10==8+2

dan
--
Dan Mack