Synchronous and Asynchronous Device Driver Modes
Original Publication Date: 1986-Apr-01
Included in the Prior Art Database: 2005-Mar-08
A method is described which allows user programs running on the UNIX operating system to dynamically select either a synchronous or asynchronous mode of operation. Programs which run on the UNIX* operating system transmit data to devices via read and write system calls. Traditionally, with character devices such as printers, plotters, locators, and the like, the mode of operation has traditionally been a synchronous one. A user program could not choose asynchronous operation. Block devices such as disks are typically run in an asynchronous mode and are not covered by this method. In synchronous operation, the user program issues the read or write system call which transfers control to the kernel device driver to perform the request. The user program does not receive control back until the operation is complete.