The following sections contain descriptions of the pointer relationships maintained by the kernel and the various data structures used in STREAMS drivers. When the kernel accesses a driver, it uses a sequence of pointers in various data structures. It looks first at the data structure relationship, and then the entry point interface for loading the driver into the kernel and accessing the driver from the application level.
The order of data structures the kernel uses to get to a driver is as follows:
Contains the revision number and a list of drivers to dynamically load. It is used by mod_install in the _init routine to load the module into the kernel. Points to a modldrv(9S) or modlstrmod(9S).
Contains information about the driver being loaded and points to the devops structure.
Points to an fmodsw(9S) structure (which points to a streamtab(9S)). Only used by STREAMS modules.
Contains list of entry points for a driver, such as attach, and info. Also points to a cb_ops(9S) structure.
Points to list of threadable entry points to driver, like open, close, read, write, ioctl. Also points to the streamtab.
Points to the entry points of the STREAMS portion of the driver, such as put, srv, open, close, as well as the mod_info structure. These entry points only process messages.
Each STREAMS driver or module contains the linkage connections for the various data structures which is a list of pointers to dev_ops(9S) structures. In each dev_ops(9S) structure is a pointer to the cb_ops(9S) structure. In the cb_ops(9S) structure contains a pointer to the streamtab struct. If the driver is not a STREAMS driver, streamtab is NULL. If the driver is a STREAMS driver, streamtab contains initialization routines for the driver.