<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"> <HTML ><HEAD ><TITLE >User-level or kernel-level driver?</TITLE ><META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.7"><LINK REL="HOME" TITLE="The Linux 2.4 Parallel Port Subsystem" HREF="book1.html"><LINK REL="UP" TITLE="User-level device drivers" HREF="c587.html"><LINK REL="PREVIOUS" TITLE="User-level device drivers" HREF="c587.html"><LINK REL="NEXT" TITLE="Programming interface" HREF="x623.html"></HEAD ><BODY CLASS="SECT1" BGCOLOR="#FFFFFF" TEXT="#000000" LINK="#0000FF" VLINK="#840084" ALINK="#0000FF" ><DIV CLASS="NAVHEADER" ><TABLE SUMMARY="Header navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TH COLSPAN="3" ALIGN="center" >The Linux 2.4 Parallel Port Subsystem</TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="bottom" ><A HREF="c587.html" ACCESSKEY="P" ><<< Previous</A ></TD ><TD WIDTH="80%" ALIGN="center" VALIGN="bottom" >User-level device drivers</TD ><TD WIDTH="10%" ALIGN="right" VALIGN="bottom" ><A HREF="x623.html" ACCESSKEY="N" >Next >>></A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><DIV CLASS="SECT1" ><H1 CLASS="SECT1" ><A NAME="AEN619" ></A >User-level or kernel-level driver?</H1 ><P > The decision of whether to choose to write a kernel-level device driver or a user-level device driver depends on several factors. One of the main ones from a practical point of view is speed: kernel-level device drivers get to run faster because they are not preemptable, unlike user-level applications. </P ><P > Another factor is ease of development. It is in general easier to write a user-level driver because (a) one wrong move does not result in a crashed machine, (b) you have access to user libraries (such as the C library), and (c) debugging is easier. </P ></DIV ><DIV CLASS="NAVFOOTER" ><HR ALIGN="LEFT" WIDTH="100%"><TABLE SUMMARY="Footer navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" ><A HREF="c587.html" ACCESSKEY="P" ><<< Previous</A ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="book1.html" ACCESSKEY="H" >Home</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><A HREF="x623.html" ACCESSKEY="N" >Next >>></A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >User-level device drivers</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="c587.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >Programming interface</TD ></TR ></TABLE ></DIV ></BODY ></HTML >