The IOS requestor service functions carry various tasks for drivers and clients. There are the following requestor service functions:
| IRS_FIRSTNXT_CHAR_DEV (9) | Returns the name of a character device. |
| IRS_GET_DRVINFO (2) | Returns information about the given drive. |
| IRS_GET_LOGICAL_DRVS (7) | Returns logical volumes on the given INT 13h unit. |
| IRS_GET_VRP (0) | Returns the VRP for a volume. |
| IRS_IS_DRVCOMPRESSED (10) | Returns a host drive if the given drive is compressed. |
| IRS_MEDIA_CHECK_RESET (3) | Checks media and resets changeline. |
| IRS_MOUNT_NOTIFY (8) | Notifies that a drive was just mounted. |
| IRS_QUERY_VOLUME_LOCK (6) | Notifies that the volume is about to be locked. |
| IRS_REAL_MODE_HANDOFF (5) | Notifies that real mode is about to take over. |
| IRS_REPLACE_VRP (1) | Replaces the currently active VRP. |
| IRS_SET_CUR_FLP_UNIT (4) | Sets the current floppy unit on single floppy systems. |
A driver or client uses a function by passing the address of an IOS requestor service structure (IRS) to the IOS_Requestor_Service service. The content and format of the structure to pass to the service varies from function to function, but all structures start with a standard header as defined by the IRS structure. This structure includes the IRS_func member that identifies the function to carry out and the IRS_result member that the IOS uses to indicate whether it completed the function or encountered an error. The driver should check the value of IRS_result after the IOS returns.
IOS_Requestor_Service, IRS, VRP