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<!-- Copyright (C) 2003 Red Hat, Inc. --> <!-- This material may be distributed only subject to the terms --> <!-- and conditions set forth in the Open Publication License, v1.0 --> <!-- or later (the latest version is presently available at --> <!-- http://www.opencontent.org/openpub/). --> <!-- Distribution of the work or derivative of the work in any --> <!-- standard (paper) book form is prohibited unless prior --> <!-- permission is obtained from the copyright holder. --> <HTML ><HEAD ><TITLE >Device Driver Interface to the Kernel</TITLE ><meta name="MSSmartTagsPreventParsing" content="TRUE"> <META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.76b+ "><LINK REL="HOME" TITLE="eCos Reference Manual" HREF="ecos-ref.html"><LINK REL="UP" TITLE="I/O Package (Device Drivers)" HREF="io.html"><LINK REL="PREVIOUS" TITLE="Serial testing with ser_filter" HREF="io-serial-testing-with-serfilter.html"><LINK REL="NEXT" TITLE="Synchronization" HREF="devapi-synchronization.html"></HEAD ><BODY CLASS="CHAPTER" 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" >eCos Reference Manual</TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="bottom" ><A HREF="io-serial-testing-with-serfilter.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="80%" ALIGN="center" VALIGN="bottom" ></TD ><TD WIDTH="10%" ALIGN="right" VALIGN="bottom" ><A HREF="devapi-synchronization.html" ACCESSKEY="N" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><DIV CLASS="CHAPTER" ><H1 ><A NAME="DEVAPI-DEVICE-DRIVER-INTERFACE-TO-THE-KERNEL">Chapter 18. Device Driver Interface to the Kernel</H1 ><DIV CLASS="TOC" ><DL ><DT ><B >Table of Contents</B ></DT ><DT ><A HREF="devapi-device-driver-interface-to-the-kernel.html#DEVAPI-INTERRUPT-MODEL" >Interrupt Model</A ></DT ><DT ><A HREF="devapi-synchronization.html" >Synchronization</A ></DT ><DT ><A HREF="devapi-smp-support.html" >SMP Support</A ></DT ><DT ><A HREF="devapi-device-driver-models.html" >Device Driver Models</A ></DT ><DT ><A HREF="devapi-synchronization-levels.html" >Synchronization Levels</A ></DT ><DT ><A HREF="devapi-api.html" >The API</A ></DT ></DL ></DIV ><P >This chapter describes the API that device drivers may use to interact with the kernel and HAL. It is primarily concerned with the control and management of interrupts and the synchronization of ISRs, DSRs and threads.</P ><P >The same API will be present in configurations where the kernel is not present. In this case the functions will be supplied by code acting directly on the HAL.</P ><DIV CLASS="SECTION" ><H1 CLASS="SECTION" ><A NAME="DEVAPI-INTERRUPT-MODEL">Interrupt Model</H1 ><P ><SPAN CLASS="emphasis" ><I CLASS="EMPHASIS" >eCos</I ></SPAN > presents a three level interrupt model to device drivers. This consists of Interrupt Service Routines (ISRs) that are invoked in response to a hardware interrupt; Deferred Service Routines (DSRs) that are invoked in response to a request by an ISR; and threads that are the clients of the driver. </P ><P >Hardware interrupts are delivered with minimal intervention to an ISR. The HAL decodes the hardware source of the interrupt and calls the ISR of the attached interrupt object. This ISR may manipulate the hardware but is only allowed to make a restricted set of calls on the driver API. When it returns, an ISR may request that its DSR should be scheduled to run.</P ><P >A DSR will be run when it is safe to do so without interfering with the scheduler. Most of the time the DSR will run immediately after the ISR, but if the current thread is in the scheduler, it will be delayed until the thread is finished. A DSR is allowed to make a larger set of driver API calls, including, in particular, being able to call <TT CLASS="FUNCTION" >cyg_drv_cond_signal()</TT > to wake up waiting threads.</P ><P >Finally, threads are able to make all API calls and in particular are allowed to wait on mutexes and condition variables. </P ><P >For a device driver to receive interrupts it must first define ISR and DSR routines as shown below, and then call <TT CLASS="FUNCTION" >cyg_drv_interrupt_create()</TT >. Using the handle returned, the driver must then call <TT CLASS="FUNCTION" >cyg_drv_interrupt_attach()</TT > to actually attach the interrupt to the hardware vector.</P ></DIV ></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="io-serial-testing-with-serfilter.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="ecos-ref.html" ACCESSKEY="H" >Home</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><A HREF="devapi-synchronization.html" ACCESSKEY="N" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >Serial testing with ser_filter</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="io.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >Synchronization</TD ></TR ></TABLE ></DIV ></BODY ></HTML >