Provides access to the SCSI tmscsi device driver.
The tmscsi special file provides an interface to allow processor-to-processor data transfer using the SCSI send command. This single device driver handles both SCSI initiator and SCSI target mode roles.
The user accesses the data transfer functions through the special files /dev/tmscsi0.xx, /dev/tmscsi1.xx, .... These are all character special files. The xx variable can be either im, initiator-mode interface, or tm, target-mode interface. The initiator-mode interface transmits data, and the target-mode interface receives data.
The least significant bit of the minor device number indicates to the device driver which mode interface is selected by the caller. When the least significant bit of the minor device number is set to 1, the target-mode interface is selected. When the least significant bit is set to 0, the initiator-mode interface is selected.
When the caller opens the initiator-mode special file, a logical path is established allowing data to be transmitted. The write, writex, writev, or writevx subroutine initiates data transmission for a user-mode caller, and the fp_write or fp_rwuio kernel services initiate data transmission for a kernel-mode caller. The SCSI target-mode device driver then builds a SCSI send command to describe the transfer, and the data is sent to the device. Once the write entry point returns, the calling program can access the transmit buffer.
When the caller opens the target-mode special file, a logical path is established allowing data to be received. The read, readx, readv, or readvx subroutine initiates data reception for a user-mode caller, and the fp_read or fp_rwuio kernel service initiates data reception for a kernel-mode caller. The SCSI target-mode device driver then returns data received for the application.
The close subroutine, open subroutine, read or readx subroutine, write or writex subroutine.
SCSI Target-Mode Overview in AIX 5L Version 5.2 Kernel Extensions and Device Support Programming Concepts.