SYS_QDVSW sysconfig Operation
Purpose
Checks the status of a device switch entry in the device switch table.
Description
The SYS_QDVSW sysconfig operation checks the status of a device switch entry in the device switch table.
The parmp parameter on the sysconfig subroutine points to a qry_devsw structure defined in the sys/sysconfig.h file. The parmlen parameter on the subroutine should be set to the length of the qry_devsw structure.
The qry_devsw field in the qry_devsw structure is modified to reflect the status of the device switch entry specified by the qry_devsw field. ( Only the major portion of the devno field is relevant.) The following flags can be returned in the status field:
| Item | Description |
|---|---|
| DSW_UNDEFINED | The device switch entry is not defined if this flag has a value of 0 on return. |
| DSW_DEFINED | The device switch entry is defined. |
| DSW_CREAD | The device driver in this device switch entry provides a routine for character reads or raw input. This flag is set when the device driver provides a ddread entry point. |
| DSW_CWRITE | The device driver in this device switch entry provides a routine for character writes or raw output. This flag is set when the device driver provides a ddwrite entry point. |
| DSW_BLOCK | The device switch entry is defined by a block device driver. This flag is set when the device driver provides a ddstrategy entry point. |
| DSW_MPX | The device switch entry is defined by a multiplexed device driver. This flag is set when the device driver provides a ddmpx entry point. |
| DSW_SELECT | The device driver in this device switch entry provides a routine for handling the select (select Subroutine) or poll subroutines. This flag is set when the device driver provides a ddselect entry point. |
| DSW_DUMP | The device driver defined by this device switch entry provides the capability to support one or more of its devices as targets for a kernel dump. This flag is set when the device driver has provided a dddump entry point. |
| DSW_CONSOLE | The device switch entry is defined by the console device driver. |
| DSW_TCPATH | The device driver in this device switch entry supports devices that are considered to be in the trusted computing path and provides support for the revoke (revoke Subroutine) and frevoke subroutines. This flag is set when the device driver provides a ddrevoke entry point. |
| DSW_OPENED | The device switch entry is defined and the device has outstanding opens. This flag is set when the device driver has at least one outstanding open. |
The DSW_UNDEFINED condition is indicated when the device switch entry has not been defined or has been defined and subsequently deleted. Multiple status flags may be set for other conditions of the device switch entry.
Return Values
If no error is detected, this operation returns with a value of 0. If an error is detected, the return value is set to a value of -1.
Error Codes
When an error is dected, the errno global variable is also set to one of the following values:
| Item | Description |
|---|---|
| EACCES | The calling process does not have the required privilege. |
| EINVAL | Device number exceeds the maximum allowed by the kernel. |
| EFAULT | The calling process does not have sufficient authority to access the data area described by the parmp and parmlen parameters provided on the system call. This error is also returned if an I/O error occurred when accessing data in this area. |
File
| Item | Description |
|---|---|
| sys/sysconfig.h | Contains structure definitions. |