The SSA_GET_ENTRY_POINT operation allows another kernel extension, typically a SSA head device driver, to determine the direct call entry point for the SSA adapter device driver. This operation is the entry point through which the head device driver communicates with the adapter device driver. The address that is supplied is valid only while the calling kernel extension holds an open file descriptor for the SSA adapter device driver. This operation is not valid for a user process.
The arg parameter specifies the address of a SSA_GetEntryPointParms_t structure in kernel address space. The SSA_GetEntryPointParms_t structure is defined in the /usr/include/sys/ssa.h file.
On completion of the operation, the fields in the SSA_GetEntryPointParms_t structure are modified as follows:
| Field | Description |
|---|---|
| EntryPoint | Address of the direct call entry point for the SSA adapter device driver, which is used to submit operations from a head device driver. |
| InterruptPriority | The off level interrupt priority at which the calling kernel extension is called back for completion of commands that are started by calling the direct call entry point. |
When completed successfully, this operation returns a value of 0. Otherwise, a value of -1 is returned and the errno global variable is set to the following value:
| Value | Description |
|---|---|
| EINVAL | Indicates that the caller was not in kernel mode. |
/dev/ssa0, /dev/ssa1,..., /dev/ssan