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BIO(4) Device Drivers Manual BIO(4)


bioblock I/O ioctl tunnel pseudo-device


pseudo-device bio [count]


The bio driver provides userland applications ioctl(2) access to devices otherwise not found as /dev nodes. The /dev/bio device node operates by delegating ioctl calls to a requested device driver. Only drivers which have registered with the bio device can be accessed via this interface.
If count is given in the specification, and is greater than 0, a maximum of one bio device is created.
The following device drivers register with bio for volume management:
American Megatrends Inc. MegaRAID PATA/SATA/SCSI RAID controller
Areca Technology Corporation SAS/SATA RAID controller
Compaq Smart Array 2/3/4 SCSI RAID controller
Compaq Smart Array SAS/SATA/SCSI RAID controller
IBM SATA/SCSI ServeRAID controller
LSI Logic & Dell MegaRAID SAS RAID controller
LSI Logic MegaRAID SAS Fusion RAID controller
LSI Logic Fusion-MPT Message Passing Interface
LSI Logic Fusion-MPT Message Passing Interface II
Software RAID
The following device drivers register with bio to provide enclosure management:
SCSI Accessed Fault-Tolerant Enclosure
SCSI Enclosure Services
The following ioctl calls apply to the bio device:
BIOCLOCATE struct bio_locate *
Locate a named device and give back a cookie to the application for subsequent ioctl calls. The cookie is used to tunnel further ioctls to the right device.
BIOCINQ struct bioc_inq *
Retrieve number of volumes and physical disks for a specific device.
BIOCDISK struct bioc_disk *
Retrieve detailed information for the specified physical disk. Information returned can include status, size, channel, target, lun, vendor name, serial number and processor device (ses or safte).
BIOCVOL struct bioc_vol *
Retrieve detailed information for the specified volume. Information returned can include status, size, RAID level, number of disks, device name association (sd?) and vendor name.
BIOCALARM struct bioc_alarm *
Control the alarm beeper on the device. Supported states are: disable alarm, enable alarm, silence alarm, status and test alarm.
Note: These options might not be supported on all hardware.
BIOCBLINK struct bioc_blink *
Blink an LED of the specified physical disk. Supported blink states are: blink LED, unblink LED and blink alarm LED.
Note: This option is only supported if the disk is governed by ses(4) or safte(4) and the hardware supports hardware blinking.
BIOCSETSTATE struct bioc_setstate *
Alter the state of specified physical disk. Supported states are: create hot-spare, online disk and offline disk.
The following ioctl calls apply to the bio device only when talking to a softraid(4) device:
BIOCCREATERAID struct bioc_createraid *
Create a new volume or assemble an existing volume. The volume will be attached as a system disk, if this capability is supported by the volume discipline.
BIOCDELETERAID struct bioc_deleteraid *
Remove system disk (if present) and disassemble the softraid(4) volume.
BIOCDISCIPLINE struct bioc_discipline *
Dispatch a discipline specific ioctl.
BIOCINSTALLBOOT struct bioc_installboot *
Install a boot loader.


ioctl tunnel device


ioctl(2), softraid(4), bioctl(8)


The bio driver first appeared in OpenBSD 3.2.


The bio driver was written by Niklas Hallqvist <niklas@openbsd.org>. The API was written by Marco Peereboom <marco@openbsd.org>.
November 26, 2016 OpenBSD-6.1