Generic Block Device Capability¶
This file documents the sysfs file block/<disk>/capability
.
capability
is a bitfield, printed in hexadecimal, indicating which
capabilities a specific block device supports:
genhd capability flags
GENHD_FL_REMOVABLE
(0x0001): indicates that the block device
gives access to removable media.
When set, the device remains present even when media is not
inserted.
Must not be set for devices which are removed entirely when the
media is removed.
GENHD_FL_CD
(0x0008): the block device is a CD-ROM-style
device.
Affects responses to the CDROM_GET_CAPABILITY
ioctl.
GENHD_FL_UP
(0x0010): indicates that the block device is “up”,
with a similar meaning to network interfaces.
GENHD_FL_SUPPRESS_PARTITION_INFO
(0x0020): don’t include
partition information in /proc/partitions
or in the output of
printk_all_partitions().
Used for the null block device and some MMC devices.
GENHD_FL_EXT_DEVT
(0x0040): the driver supports extended
dynamic dev_t
, i.e. it wants extended device numbers
(BLOCK_EXT_MAJOR
).
This affects the maximum number of partitions.
GENHD_FL_NATIVE_CAPACITY
(0x0080): based on information in the
partition table, the device’s capacity has been extended to its
native capacity; i.e. the device has hidden capacity used by one
of the partitions (this is a flag used so that native capacity is
only ever unlocked once).
GENHD_FL_BLOCK_EVENTS_ON_EXCL_WRITE
(0x0100): event polling is
blocked whenever a writer holds an exclusive lock.
GENHD_FL_NO_PART_SCAN
(0x0200): partition scanning is disabled.
Used for loop devices in their default settings and some MMC
devices.
GENHD_FL_HIDDEN
(0x0400): the block device is hidden; it
doesn’t produce events, doesn’t appear in sysfs, and doesn’t have
an associated bdev
.
Implies GENHD_FL_SUPPRESS_PARTITION_INFO
and
GENHD_FL_NO_PART_SCAN
.
Used for multipath devices.