+++ /dev/null
-<!-- 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 Models</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="Device Driver Interface to the Kernel"
-HREF="devapi-device-driver-interface-to-the-kernel.html"><LINK
-REL="PREVIOUS"
-TITLE="SMP Support"
-HREF="devapi-smp-support.html"><LINK
-REL="NEXT"
-TITLE="Synchronization Levels"
-HREF="devapi-synchronization-levels.html"></HEAD
-><BODY
-CLASS="SECTION"
-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="devapi-smp-support.html"
-ACCESSKEY="P"
->Prev</A
-></TD
-><TD
-WIDTH="80%"
-ALIGN="center"
-VALIGN="bottom"
->Chapter 18. Device Driver Interface to the Kernel</TD
-><TD
-WIDTH="10%"
-ALIGN="right"
-VALIGN="bottom"
-><A
-HREF="devapi-synchronization-levels.html"
-ACCESSKEY="N"
->Next</A
-></TD
-></TR
-></TABLE
-><HR
-ALIGN="LEFT"
-WIDTH="100%"></DIV
-><DIV
-CLASS="SECTION"
-><H1
-CLASS="SECTION"
-><A
-NAME="DEVAPI-DEVICE-DRIVER-MODELS">Device Driver Models</H1
-><P
->There are several ways in which device drivers
-may be built. The exact model chosen will depend on the properties of
-the device and the behavior desired. There are three basic models that
-may be adopted.</P
-><P
->The first model is to do all device processing in the ISR. When it is
-invoked the ISR programs the device hardware directly and accesses
-data to be transferred directly in memory. The ISR should also call
-<TT
-CLASS="FUNCTION"
->cyg_drv_interrupt_acknowledge()</TT
->. When it is
-finished it may optionally request that its DSR be invoked. The DSR
-does nothing but call <TT
-CLASS="FUNCTION"
->cyg_drv_cond_signal()</TT
-> to
-cause a thread to be woken up. Thread level code must call
-<TT
-CLASS="FUNCTION"
->cyg_drv_isr_lock()</TT
->, or
-<TT
-CLASS="FUNCTION"
->cyg_drv_interrupt_mask()</TT
-> to prevent ISRs running
-while it manipulates shared memory.</P
-><P
->The second model is to defer device processing to the DSR. The ISR
-simply prevents further delivery of interrupts by either programming
-the device, or by calling
-<TT
-CLASS="FUNCTION"
->cyg_drv_interrupt_mask()</TT
->. It must then call
-<TT
-CLASS="FUNCTION"
->cyg_drv_interrupt_acknowledge()</TT
-> to allow other
-interrupts to be delivered and then request that its DSR be
-called. When the DSR runs it does the majority of the device handling,
-optionally signals a condition variable to wake a thread, and finishes
-by calling <TT
-CLASS="FUNCTION"
->cyg_drv_interrupt_unmask()</TT
-> to re-allow
-device interrupts. Thread level code uses
-<TT
-CLASS="FUNCTION"
->cyg_drv_dsr_lock()</TT
-> to prevent DSRs running while
-it manipulates shared memory. The eCos serial device drivers use this
-approach.</P
-><P
->The third model is to defer device processing even further to a
-thread. The ISR behaves exactly as in the previous model and simply
-blocks and acknowledges the interrupt before request that the DSR
-run. The DSR itself only calls
-<TT
-CLASS="FUNCTION"
->cyg_drv_cond_signal()</TT
-> to wake the thread. When
-the thread awakens it performs all device processing, and has full
-access to all kernel facilities while it does so. It should finish by
-calling <TT
-CLASS="FUNCTION"
->cyg_drv_interrupt_unmask()</TT
-> to re-allow
-device interrupts. The eCos ethernet device drivers are written to
-this model.</P
-><P
->The first model is good for devices that need immediate processing and
-interact infrequently with thread level. The second model trades a
-little latency in dealing with the device for a less intrusive
-synchronization mechanism. The last model allows device processing to
-be scheduled with other threads and permits more complex device
-handling.</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="devapi-smp-support.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-levels.html"
-ACCESSKEY="N"
->Next</A
-></TD
-></TR
-><TR
-><TD
-WIDTH="33%"
-ALIGN="left"
-VALIGN="top"
->SMP Support</TD
-><TD
-WIDTH="34%"
-ALIGN="center"
-VALIGN="top"
-><A
-HREF="devapi-device-driver-interface-to-the-kernel.html"
-ACCESSKEY="U"
->Up</A
-></TD
-><TD
-WIDTH="33%"
-ALIGN="right"
-VALIGN="top"
->Synchronization Levels</TD
-></TR
-></TABLE
-></DIV
-></BODY
-></HTML
->
\ No newline at end of file
projects / karo-tx-redboot.git / blobdiff