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AIX Version 4.3 Kernel and Subsystems Technical Reference, Volume 2
scsesdd SCSI Device Driver
Purpose
Device driver supporting the SCSI Enclosure Services device.
Syntax
#include <sys/devinfo.h>
#include <sys/scsi.h>
#include <sys/scses.h>
Description
The special files /dev/ses0, /dev/ses1, ..., provide I/O access and control functions to the SCSI enclosure devices.
Typical SCSI enclosure services operations are implemented using the open, ioctl, and close subroutines.
Open places the selected device in Exclusive Access mode. This mode is singularly entrant; that is, only one process at a time can open it.
A device can be opened only if the device is not currently opened. If an attempt is made to open a device and the device is already open, a value of -1 is returned and the errno global variable is set to a value of EBUSY.
ioctl Subroutine
The following ioctl operation are available for SCSI Enclosure Services devices:
| IOCINFO |
Returns the devinfo structure defined in the /usr/include/sys/devinfo.h file. |
| SESIOCMD |
When the device has been successfully opened, this operation provides the means for issuing any SCSI command to the specified enclosure. The device driver performs no error recovery or logging-on failures of this ioctl operation.
The SCSI status byte and the adapter status bytes are returned via the arg parameter, which contains the address of a sc_iocmd structure (defined in the /usr/include/sys/scsi.h file). If the SESIOCMD operation returns a value of -1 and the errno global variable is set to a nonzero value, the requested operation has failed. In this case, the caller should evaluate the returned status bytes to determine why the operation failed and what recovery actions should be taken.
The devinfo structure defines the maximum transfer size for the command. If an attempt is made to transfer more than the maximum, a value of -1 is returned and the errno global variable set to a value of EINVAL. Refer to the Small Computer System Interface (SCSI) Specification for the applicable device to get request sense information. |
Device Requirements
The following hardware requirements exist for SCSI enclosure services devices on AIX:
- The device must support the SCSI-3 Enclosure Services Specification Revision 4 or later.
- The device can be addressed from a SCSI id different from the SCSI ids of the the SCSI devices inside the enclosure.
- The device must be "well behaved", when receiving SCSI inquiries to page code 0xC7. This means that if the device fails the inquiry to page code C7 with a check condition, then the check condition will be cleared by the next SCSI command. An explicit request sense is not required.
- If the device reports its ANSI version to be 3 (SCSI-3) in the standard inquiry data, then it must correctly reject all invalid requests for luns 8-31 (that is,the device cannot ignore the upper bits in Lun id and thus cannot treat Lun 8 as being Lun 0, etc).
Error Conditions
Ioctl and open subroutines against this device fail in the following circumstances:
| EBUSY |
An attempt was made to open a device already opened. |
| EFAULT |
An illegal user address was entered. |
| EINVAL |
The data buffer length exceeded the maximum defined in the devinfo structure for a SESIOCMD ioctl operation. |
| EINVAL |
An unsupported ioctl operation was attempted. |
| EINVAL |
An attempt was made to configure a device that is still open. |
| EINVAL |
An illegal configuration command has been given. |
| EIO |
The target device cannot be located or is not responding. |
| EIO |
The target device has indicated an unrecovered hardware error. |
| EMFILE |
An open was attempted for an adapter that already has the maximum permissible number of opened devices. |
| ENODEV |
An attempt was made to access a device that is not defined. |
| ENODEV |
An attempt was made to close a device that has not been defined. |
| ENXIO |
The ioctl subroutine supplied an invalid parameter. |
| EPERM |
The attempted subroutine requires appropriate authority. |
| ETIMEDOUT |
An I/O operation has exceeded the given timer value. |
Reliability and Serviceability Information
The following errors are returned from SCSI enclosure services devices:
| ABORTED COMMAN |
The device cancelled the command. |
| ADAPTER ERRORS |
The adapter returned an error. |
| GOOD COMPLETION |
The command completed successfully. |
| HARDWARE ERROR |
An unrecoverable hardware failure occurred during command execution or during a self test. |
| ILLEGAL REQUEST |
An illegal command or command parameter. |
| MEDIUM ERROR |
The command terminated with a unrecovered media error condition. |
| NOT READY |
The logical unit is off-line or media is missing. |
| RECOVERED ERROR |
The command was successful after some recovery applied. |
| UNIT ATTENTION |
The device has been reset or the power has been turned on. |
Files
| /dev/ses0,/dev/ses1...,/dev/sesn |
Provides an interface to allow SCSI device drivers access to SCSI enclosure services devices. |
Related Information
SCSI Subsystem Overview in AIX Version 4.3 Kernel Extensions and Device Support Programming Concepts.
A Typical Initiator-Mode SCSI Driver Transaction Sequence in AIX Version 4.3 Kernel Extensions and Device Support Programming Concepts.
Required SCSI Adapter Device Driver ioctl Commands in AIX Version 4.3 Kernel Extensions and Device Support Programming Concepts.
Understanding the Execution of Initiator I/O Requests in AIX Version 4.3 Kernel Extensions and Device Support Programming Concepts.
SCSI Error Recovery in AIX Version 4.3 Kernel Extensions and Device Support Programming Concepts.
Understanding the sc_buf Structure in AIX Version 4.3 Kernel Extensions and Device Support Programming Concepts.
SCSI Adapter Device Driver.
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