Generic Block Device Capability¶
This file documents the sysfs file
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
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
Affects responses to the
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
Used for the null block device and some MMC devices.
GENHD_FL_EXT_DEVT (0x0040): the driver supports extended
dev_t, i.e. it wants extended device numbers
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
GENHD_FL_HIDDEN (0x0400): the block device is hidden; it
doesn’t produce events, doesn’t appear in sysfs, and doesn’t have
Used for multipath devices.
allocate a gendisk structure
numa node to allocate on
Allocate and pre-initialize a gendisk structure for use with BIO based drivers.