Device Driver and Adapter Device Driver Interfaces

The device drivers can have both character (raw) and block special files in the /dev directory.

The adapter device driver has only character (raw) special files in the /dev directory and has only the ddconfig, ddopen, ddclose, dddump, and ddioctl entry points available to operating system programs. The ddread and ddwrite entry points are not implemented.

Internally, the devsw table has entry points for the ddconfig, ddopen, ddclose, dddump, ddioctl, and ddstrat routines. The device drivers pass their commands to the adapter device driver by calling the adapter device driver ddstrat routine. (This routine is unavailable to other operating system programs due to the lack of a block-device special file.)

Access to the adapter device driver's ddconfig, ddopen, ddclose, dddump, ddioctl, and ddstrat entry points by the device drivers is performed through the kernel services provided. These include such services as fp_opendev, fp_close, fp_ioctl, devdump, and devstrat.