Compaq Tru64 UNIX User manual

Tru64 UNIX
Writing Network Device Drivers
Part Number: AA-RNG2A-TE
December 2000
Product Version: Device Driver Kit Version 2.0
Operating System and Version: Tru64 UNIX Version 5.0A or higher
This manual contains information that systems engineers need to write
network device drivers that operate on any bus.
Compaq Computer Corporation
Houston, Texas

© 2000 Compaq Computer Corporation
Compaq and the Compaq logo Registered in U.S. Patent and Trademark Office. Tru64 is a trademark of
Compaq Information Technologies Group, L.P. in the United States and other countries.
UNIX and X/Open are trademarks of The Open Group in the United States and other countries. All other
product names mentioned herein may be trademarks of their respective companies.
Confidential computer software. Valid license from Compaq required for possession, use, or copying.
Consistent with FAR 12.211 and 12.212, Commercial Computer Software, Computer Software
Documentation, and Technical Data for Commercial Items are licensed to the U.S. Government under
vendor’s standard commercial license.
Compaq shall not be liable for technical or editorial errors or omissions contained herein. The information
in this document is provided “as is” without warranty of any kind and is subject to change without
notice. The warranties for Compaq products are set forth in the express limited warranty statements
accompanying such products. Nothing herein should be construed as constituting an additional warranty.

Contents
About This Manual
1 Network Device Driver Environment
1.1 Include Files Section for a Network Driver ....................... 1–3
1.2 Declarations Section for a Network Driver ....................... 1–4
1.2.1 External and Forward Declarations .......................... 1–5
1.2.2 Declaring softc and controller Data Structure Arrays ...... 1–6
1.2.3 Declaring and Initializing the driver Data Structure ...... 1–7
1.2.4 Defining Driver-Specific Macros ............................... 1–7
1.3 Configure Section for a Network Driver ........................... 1–10
1.4 Autoconfiguration Support Section for a Network Driver ...... 1–10
1.5 Initialization Section for a Network Driver ....................... 1–10
1.6 Start Section for a Network Driver ................................ 1–10
1.7 Watchdog Section for a Network Driver ........................... 1–11
1.8 Reset Section for a Network Driver ................................ 1–11
1.9 ioctl Section for a Network Driver .................................. 1–11
1.10 Interrupt Section for a Network Driver ........................... 1–11
1.11 Output Section for a Network Driver .............................. 1–11
2 Defining Device Register Offsets
2.1 Interrupt and Status Register Offset Definitions ................ 2–1
2.2 Command Port Register Offset Definitions ....................... 2–2
2.3 Window 0 Configuration Register Offset Definitions ............ 2–4
2.4 Window 3 Configuration Register Offset Definitions ............ 2–7
2.5 Window 1 Operational Register Offset Definitions .............. 2–9
2.6 Window 4 Diagnostic Register Offset Definitions ................ 2–11
2.7 EEPROM Data Structure Definition .............................. 2–13
3 Defining the softc Data Structure
3.1 Defining Common Information ..................................... 3–2
3.2 Enabling Support for Enhanced Hardware Management ...... 3–4
3.3 Defining Media State Information ................................. 3–4
3.4 Defining the Base Register .......................................... 3–6
3.5 Defining Multicast Table Information ............................. 3–6
Contents iii

3.6 Defining the Interrupt Handler ID ................................. 3–6
3.7 Defining CSR Pointer Information ................................. 3–6
3.8 Defining FIFO Maintenance Information ......................... 3–7
3.9 Defining Bus-Specific Information ................................. 3–7
3.10 Defining the Broadcast Flag ........................................ 3–8
3.11 Defining the Debug Flag ............................................. 3–8
3.12 Defining Interrupt and Timeout Statistics ....................... 3–8
3.13 Defining Autosense Kernel Thread Context Information ...... 3–9
3.14 Defining the Polling Context Flag .................................. 3–9
3.15 Defining a Copy of the w3_eeprom Data Structure .............. 3–10
3.16 Declaring the Simple Lock Data Structure ....................... 3–10
4 Implementing the Configure Section
4.1 Declaring Configure-Related Variables and the
cfg_subsys_attr_t Data Structure .................................. 4–1
4.2 Setting Up the el_configure Routine ............................... 4–3
5 Implementing the Autoconfiguration Support Section (probe)
5.1 Implementing the el_probe Routine ............................... 5–1
5.1.1 Setting Up the el_probe Routine ............................... 5–2
5.1.2 Checking the Maximum Number of Devices That the
Driver Supports .................................................. 5–4
5.1.3 Performing Bus-Specific Tasks ................................. 5–4
5.1.4 Allocating Memory for the softc Data Structure ............ 5–6
5.1.5 Allocating the ether_driver Data Structure .................. 5–7
5.1.6 Initializing the Enhanced Hardware Management Data
Structure .......................................................... 5–8
5.1.7 Computing the CSR Addresses ................................ 5–8
5.1.8 Setting Bus-Specific Data Structure Members .............. 5–8
5.1.9 Handling First-Time Probe Operations ....................... 5–10
5.1.10 Handling Subsequent Probe Operations ..................... 5–12
5.1.11 Registering the Interrupt Handler ............................ 5–14
5.1.12 Saving the controller and softc Data Structure Pointers .. 5–16
5.1.13 Trying to Allocate Another controller Data Structure ...... 5–16
5.1.14 Registering the shutdown Routine ............................ 5–17
5.2 Implementing the el_shutdown Routine .......................... 5–17
5.3 Implementing the el_autosense_thread Routine ................. 5–17
5.3.1 Setting Up the el_autosense_thread Routine ................ 5–19
5.3.2 Blocking Until Awakened ....................................... 5–19
5.3.3 Testing for the Termination Flag .............................. 5–20
5.3.4 Starting Up Statistics ........................................... 5–20
iv Contents

5.3.5 Entering the Packet Transmit Loop ........................... 5–20
5.3.6 Saving Counters Prior to the Transmit Operation .......... 5–21
5.3.7 Allocating Memory for a Test Packet .......................... 5–21
5.3.8 Using the Default from the ROM .............................. 5–21
5.3.9 Setting the Media in the Hardware ........................... 5–22
5.3.10 Building the Test Packet ........................................ 5–22
5.3.11 Transmitting the Test Packet .................................. 5–22
5.3.12 Setting a Timer for the Current Kernel Thread ............. 5–23
5.3.13 Testing for Loss of Carrier ...................................... 5–23
5.3.14 Determining Whether Packets Were Transmitted
Successfully ....................................................... 5–24
5.3.15 Printing Debug Information .................................... 5–24
5.3.16 Setting Up New Media .......................................... 5–24
5.3.17 Establishing the Media .......................................... 5–25
6 Implementing the Autoconfiguration Support Section (attach)
6.1 Setting Up the el_attach Routine .................................. 6–1
6.2 Initializing the Media Address and Media Header Lengths ... 6–2
6.3 Setting Up the Media ................................................ 6–3
6.4 Initializing Simple Lock Information .............................. 6–5
6.5 Printing a Success Message ......................................... 6–6
6.6 Specifying the Network Driver Interfaces ........................ 6–6
6.7 Setting the Baud Rate ............................................... 6–8
6.8 Attaching to the Packet Filter and the Network Layer ......... 6–8
6.9 Setting Network Attributes and Registering the Adapter ...... 6–9
6.10 Handling the Reinsert Operation .................................. 6–9
6.11 Enabling the Interrupt Handler .................................... 6–10
6.12 Starting the Polling Process ......................................... 6–10
7 Implementing the unattach Routine
7.1 Setting Up the el_unattach Routine ............................... 7–1
7.2 Verifying That the Interface Has Shut Down .................... 7–2
7.3 Obtaining the Simple Lock and Shutting Down the Device .... 7–2
7.4 Disabling the Interrupt Handler ................................... 7–3
7.5 Terminating the Autosense Kernel Thread ....................... 7–3
7.6 Unregistering the PCMCIA Event Callback Routine ........... 7–4
7.7 Stopping the Polling Process ........................................ 7–4
7.8 Unregistering the Shutdown Routine ............................. 7–4
7.9 Terminating the Simple Lock ....................................... 7–4
Contents v

7.10 Unregistering the Card from the Hardware Management
Database ............................................................... 7–5
7.11 Freeing Resources .................................................... 7–5
8 Implementing the Initialization Section
8.1 Implementing the el_init Routine .................................. 8–1
8.1.1 Setting Up the el_init Routine ................................. 8–1
8.1.2 Determining Whether the PCMCIA Card Is Present ....... 8–2
8.1.3 Setting the IPL and Obtaining the Simple Lock ............ 8–2
8.1.4 Calling the el_init_locked Routine ............................ 8–3
8.1.5 Releasing the Simple Lock and Resetting the IPL .......... 8–3
8.1.6 Returning the Status from the el_init_locked Routine ..... 8–3
8.2 Implementing the el_init_locked Routine ......................... 8–3
8.2.1 Resetting the Transmitter and Receiver ...................... 8–4
8.2.2 Clearing Interrupts .............................................. 8–4
8.2.3 Starting the Device .............................................. 8–5
8.2.4 Ensuring That the 10Base2 Transceiver Is Off .............. 8–5
8.2.5 Setting the LAN Media .......................................... 8–6
8.2.6 Setting a LAN Attribute ........................................ 8–7
8.2.7 Selecting Memory Mapping .................................... 8–7
8.2.8 Resetting the Transmitter and Receiver Again .............. 8–7
8.2.9 Setting the LAN Address ....................................... 8–8
8.2.10 Processing Special Flags ........................................ 8–8
8.2.11 Setting the Debug Flag .......................................... 8–9
8.2.12 Enabling TX and RX ............................................. 8–9
8.2.13 Enabling Interrupts ............................................. 8–10
8.2.14 Setting the Operational Window .............................. 8–10
8.2.15 Marking the Device as Running ............................... 8–10
8.2.16 Starting the Autosense Kernel Thread ....................... 8–11
8.2.17 Starting the Transmit of Pending Packets ................... 8–11
9 Implementing the Start Section
9.1 Implementing the el_start Routine ................................ 9–1
9.1.1 Setting the IPL and Obtaining the Simple Lock ............ 9–1
9.1.2 Calling the el_start_locked Routine ........................... 9–2
9.1.3 Releasing the Simple Lock and Resetting the IPL .......... 9–2
9.2 Implementing the el_start_locked Routine ....................... 9–3
9.2.1 Discarding All Transmits After the User Removes the
PCMCIA Card .................................................... 9–3
9.2.2 Removing Packets from the Pending Queue and Preparing
the Transmit Buffer .............................................. 9–4
vi Contents

9.2.3 Transmitting the Buffer ......................................... 9–6
9.2.4 Accounting for Outgoing Bytes ................................. 9–7
9.2.5 Updating Counters, Freeing the Transmit Buffer, and
Marking the Output Process as Active ....................... 9–7
9.2.6 Indicating When to Start the Watchdog Routine ............ 9–8
10 Implementing a Watchdog Section
10.1 Setting the IPL and Obtaining the Simple Lock ................. 10–1
10.2 Incrementing the Transmit Timeout Counter and Resetting
the Unit ................................................................ 10–2
10.3 Releasing the Simple Lock and Resetting the IPL ............... 10–2
11 Implementing the Reset Section
11.1 Implementing the el_reset Routine ................................ 11–1
11.2 Implementing the el_reset_locked Routine ....................... 11–2
12 Implementing the ioctl Section
12.1 Setting Up the el_ioctl Routine ..................................... 12–2
12.2 Determining Whether the User Has Removed the PCMCIA
Card from the Slot .................................................... 12–3
12.3 Setting the IPL and Obtaining the Simple Lock ................. 12–3
12.4 Enabling Loopback Mode (SIOCENABLBACK ioctl
Command) ............................................................. 12–4
12.5 Disabling Loopback Mode (SIOCDISABLBACK ioctl
Command) ............................................................. 12–4
12.6 Reading Current and Default MAC Addresses
(SIOCRPHYSADDR ioctl Command) .............................. 12–5
12.7 Setting the Local MAC Address (SIOCSPHYSADDR ioctl
Command) ............................................................. 12–5
12.8 Adding the Device to a Multicast Group (SIOCADDMULTI
ioctl Command) ....................................................... 12–6
12.9 Deleting the Device from a Multicast Group (SIOCDELMULTI
ioctl Command) ....................................................... 12–7
12.10 Accessing Network Counters (SIOCRDCTRS and
SIOCRDZCTRS ioctl Commands) .................................. 12–8
12.11 Bringing Up the Device (SIOCSIFADDR ioctl Command) ..... 12–9
12.12 Using Currently Set Flags (SIOCSIFFLAGS ioctl Command) 12–10
12.13 Setting the IP MTU (SIOCSIPMTU ioctl Command) ........... 12–10
12.14 Setting the Media Speed (SIOCSMACSPEED ioctl
Command) ............................................................. 12–10
Contents vii

12.15 Resetting the Device (SIOCIFRESET ioctl Command) ......... 12–11
12.16 Setting Device Characteristics (SIOCIFSETCHAR ioctl
Command) ............................................................. 12–11
12.17 Releasing the Simple Lock and Resetting the IPL ............... 12–13
13 Implementing the Interrupt Section
13.1 Implementing the el_intr Routine .................................. 13–1
13.1.1 Setting the IPL and Obtaining the Simple Lock ............ 13–2
13.1.2 Rearming the Next Timeout .................................... 13–2
13.1.3 Reading the Interrupt Status .................................. 13–3
13.1.4 Processing Completed Receive and Transmit Operations . 13–3
13.1.5 Acknowledging the Interrupt .................................. 13–4
13.1.6 Transmitting Pending Frames ................................. 13–4
13.1.7 Releasing the Simple Lock and Resetting the IPL .......... 13–4
13.1.8 Indicating That the Interrupt Was Serviced ................. 13–5
13.2 Implementing the el_rint Routine .................................. 13–5
13.2.1 Counting the Receive Interrupt and Reading the Receive
Status .............................................................. 13–5
13.2.2 Pulling the Packets from the FIFO Buffer ................... 13–6
13.2.3 Examining the First Part of the Packet ...................... 13–7
13.2.4 Copying the Received Packet into the mbuf ................. 13–8
13.2.5 Discarding a Packet ............................................. 13–9
13.3 Implementing the el_tint Routine .................................. 13–10
13.3.1 Counting the Transmit Interrupt .............................. 13–10
13.3.2 Reading the Transmit Status and Counting All Significant
Events .............................................................. 13–10
13.3.3 Managing Excessive Data Collisions .......................... 13–11
13.3.4 Writing to the Status Register to Obtain the Next Value .. 13–11
13.3.5 Queuing Other Transmits ...................................... 13–12
13.4 Implementing the el_error Routine ................................ 13–12
14 Network Device Driver Configuration
Index
Figures
1–1Sections of a Network Device Driver ............................... 1–2
2–1Window 0 Configuration Registers ................................. 2–5
2–2Window 3 Configuration Registers ................................. 2–8
2–3Window 1 Operational Registers ................................... 2–9
viii Contents

2–4Window 4 Diagnostic Registers ..................................... 2–11
3–1Typical softc Data Structure ........................................ 3–2
3–2Mapping Alternate Names .......................................... 3–4
Tables
1–1Driver-Specific Macros ............................................... 1–9
12–1Network ioctl Commands ............................................ 12–1
12–2Network Interface Counter Types .................................. 12–9
Contents ix

About This Manual
This manual discusses how to write network device drivers for computer
systems that run the Compaq Tru64™UNIX operating system.
Audience
This manual is intended for systems engineers who:
•Use standard library routines to develop programs in the C language
•Know the Bourne shell or some other shell that is based on the UNIX
operating system
•Understand basic Tru64 UNIX concepts such as kernel, shell, process,
configuration, and autoconfiguration
•Understand how to use the Tru64 UNIX programming tools, compilers,
and debuggers
•Develop programs in an environment that involves dynamic memory
allocation, linked list data structures, and multitasking
•Understand the hardware device for which the driver is being written
•Understand the basics of the CPU hardware architecture, including
interrupts, direct memory access (DMA) operations, and I/O
Before you write a network device driver, we recommend that you be familiar
with the networking subsystem that the Tru64 UNIX operating system
provides. This manual assumes that you are familiar with the following
network interface types:
•Ethernet
•Fiber Distributed Data Interface (FDDI)
•Token Ring
See the Tru64 UNIX Technical Overview for descriptions of the data link
media.
This manual also assumes that you have some knowledge of the Tru64 UNIX
network programming environment, particularly:
•Data link provider interface
•X/Open transport interface
•Sockets
About This Manual xi

•Socket and XTI programming examples
•TCP specific programming information
•Information for Token Ring driver developers
•Data link interface
See the Tru64 UNIX Network Programmer’s Guide for descriptions of these
topics.
Scope of this Manual
This manual builds on the concepts and topics that are presented in Writing
Device Drivers, which is the core manual for developing device drivers on
Tru64 UNIX. It introduces topics that are specific to writing a device driver
for a local area network (LAN) device and that are beyond the scope of the
core manual.
In this manual, you can study a network driver called if_el. The if_el
driver supports the driver interface requirements for a LAN device,
specifically the 3Com 3C589C series PCMCIA adapter. The if_el driver
was implemented according to the specifications detailed in Ethernet III
Parallel Tasking ISA, EISA, Micro Channel, and PCMCIA Adapter Drivers
Technical Reference . This specification is published by 3Com Corporation,
and the manual part number is 09-0398-002B.
You can access the if_el source code in the device driver examples directory
(if you have installed it on your system). Ethernet is the network interface
type that is associated with the if_el driver. However, the explanations
point out where differences exist between Ethernet and other network
interfaces, including fiber distributed data interface (FDDI) and Token Ring.
The example network driver operates on multiple buses (specifically, the
PCMCIA bus and the ISA bus). It uses the common ifnet interface to
communicate with the upper layers of the Tru64 UNIX operating system.
The example does not emphasize any specific types of network device
drivers. However, mastering the concepts presented in this manual is useful
preparation for writing network device drivers that operate on a variety
of buses.
The manual does not discuss:
•How to write STREAMS network device drivers
•Topics associated with wide area networks (WANs)
•How to write an asynchronous transfer mode (ATM) device driver
•Details related to the network programming environment
xii About This Manual

New and Changed Features
This revision of the manual documents the following new features:
•Enabling support for enhanced hardware management
Enhanced hardware management (EHM) allows you to modify hardware
attributes, such as the type of LAN device, on either a local or a remote
system. See Section 3.2 for more information about how a network device
driver uses routines to define and export hardware attributes.
•The unattach( ) routine
The unattach( ) routine stops the network device and frees resources
prior to unloading the device driver or powering off the bus to which the
device is attached. See Chapter 7 for more information.
Organization
This manual is organized as follows:
Chapter 1 Describes the sections that make up a
network driver and compares them to
the sections that are associated with
block and character drivers.
Chapter 2 Describes the device register offset
definitions for the if_el device driver’s
associated LAN device, the 3Com 3C5x9
series Ethernet adapter.
Chapter 3 Describes how to define a softc data
structure, usingthe if_el devicedriver’s
el_softc structure as an example.
Chapter 4 Describes how to implement a
configure interface, using the if_el
device driver’sel_configure( )
routine as an example.
Chapter 5 Describes how to implement a probe
interface and associated routines, using
the if_el device driver’sel_probe( )
routine as an example.
Chapter 6 Describes how to implement an attach
interface, using the if_el device driver’s
el_attach( ) routine as an example.
Chapter 7 Describes how to implement an
unattach( ) routine to stop the device.
About This Manual xiii

Chapter 8 Describes how to implement an init
interface and associated routines, using
the if_el device driver’sel_init( )
routine as an example.
Chapter 9 Describes how to implement a start
interface and associated routines, using
the if_el device driver’sel_start( )
routine as an example.
Chapter 10 Describes how to implement a watchdog
interface, using the if_el device driver’s
el_watch( ) routine as an example.
Chapter 11 Describes how to implement a reset
interface and associated routines, using
the if_el device driver’sel_reset( )
routine as an example.
Chapter 12 Describes how to implement an ioctl
interface, using the if_el device driver’s
el_ioctl( ) routine as an example.
Chapter 13 Describes how to implement an
interrupt handler, using the if_el
device driver’sel_intr interrupt
handler as an example.
Chapter 14 Describes the sysconfigtab option
entries necessary for configuring network
device drivers on different bus types.
Related Documentation
The following examples and documents supplement information in this
manual.
Examples
The directory /usr/examples/ddk/src/network includes the example
source files that are used throughout this manual: if_el.c,if_elreg.h,
files, and sysconfigtab.
Manuals
The following documents provide important information that supplements
the information in this manual:
•Installation Instructions and Release Notes contains instructions on how
to install the Device Driver Kit Version 2.0 product, including source
code with examples and user manuals. It also describes changes to the
product and documentation since the Device Driver Kit Release 1.0.
xiv About This Manual

•Writing Device Drivers contains information that you need to develop
device drivers on the Compaq Tru64 UNIX operating system.
•Writing Kernel Modules describes topics for all kernel modules
such as kernel threads and writing kernel modules in a symmetric
multiprocessing (SMP) environment.
•Writing PCI Bus Device Drivers describes PCI bus-specific topics,
including PCI bus architecture and data structures that PCI bus device
drivers use.
•Writing VMEbus Device Drivers describes VMEbus-specific topics,
including VMEbus architecture and routines that VMEbus device
drivers use.
•The Guide to Preparing Product Kits describes how to create kernel
(device driver) product kits and layered product kits.
•Kernel Debugging describes how to use the dbx,kdbx, and kdebug
debuggers to find problems in kernel code. It also describes how to write
akdbx utility extension and how to create and analyze a crash dump file.
•Programming Support Tools describes several commands and utilities in
the Tru64 UNIX system, including facilities for text manipulation, macro
and program generation, and source file management.
•The Programmer’s Guide describes the programming environment of the
Tru64 UNIX operating system, with an emphasis on the C programming
language.
•The Network Programmer’s Guide describes the Tru64 UNIX network
programming environment and provides information on STREAMS
programming.
•System Administration describes how to configure, use, and maintain
the Tru64 UNIX operating system.
Reference Pages
Tru64 UNIX reference pages (also called manpages) contain descriptions of
the routines (Section 9r), data structures (Section 9s), loadable services
routines (Section 9u), and global variables (Section 9v) that apply to device
drivers.
Reader’s Comments
Compaq welcomes any comments and suggestions you have on this and
other Tru64 UNIX manuals.
You can send your comments in the following ways:
•Fax: [phone] Attn: UBPG Publications, ZKO3-3/Y32
About This Manual xv

•Internet electronic mail: [email protected]
A Reader’s Comment form is located on your system in the following
location:
/usr/doc/readers_comment.txt
Please include the following information along with your comments:
•The full title of the book and the order number. (The order number is
printed on the title page of this book and on its back cover.)
•The section numbers and page numbers of the information on which
you are commenting.
•The version of Tru64 UNIX that you are using.
•If known, the type of processor that is running the Tru64 UNIX software.
The Tru64 UNIX Publications group cannot respond to system problems
or technical support inquiries. Please address technical questions to your
local system vendor or to the appropriate Compaq technical support office.
Information provided with the software media explains how to send problem
reports to Compaq.
Conventions
This manual uses the following conventions:
.
.
.A vertical ellipsis indicates that a portion of an
example that would normally be present is not
shown.
... In syntax definitions, a horizontal ellipsis indicates
that the preceding item can be repeated one or
more times.
file Italic (slanted) type indicates variable values,
placeholders, and function parameter names.
buf In function definitions and syntax definitions used in
driver configuration, this typeface indicates names
that you must type exactly as shown.
[] In formal parameter declarations in function
definitions and in structure declarations, brackets
indicate arrays. Brackets also specify ranges for
device minor numbers and device special files in
file fragments. However, for the syntax definitions
xvi About This Manual

that are used in driver configuration, these brackets
indicate items that are optional.
| Vertical bars separating items that appear in the
syntax definitions used in driver configuration
indicate that you choose one item from among those
listed.
About This Manual xvii

1
Network Device Driver Environment
A network device is responsible for both transmitting and receiving frames
over the network media. Network devices have network device drivers
associated with them. A network device driver attaches a network subsystem
to a network interface, prepares the network interface for operation, and
governs the transmission and reception of network frames over the network
interface. Examples of network interface types include Ethernet, Fiber
Distributed Data Interface (FDDI), and Token Ring.
Similar to the character and block device drivers that are discussed in
Writing Device Drivers, a network device driver has the following sections:
•An include files section (Section 1.1)
•A declarations section (Section 1.2)
•A configure section (Section 1.3)
•An autoconfiguration support section (Section 1.4)
•An ioctl section (Section 1.9)
•An interrupt section (Section 1.10)
Similar to a character device driver, a network device driver can also have a
reset section (Section 1.8).
Unlike a character or block device driver, a network device driver contains
the following network driver-specific sections:
•An initialization section (Section 1.5)
•A start transmit section (Section 1.6)
•A watchdog section (Section 1.7)
•An output section (Section 1.11)
Figure 1–1 shows the sections that a typical network device driver can
contain. Network device drivers are not required to have all of these
sections, and more complex network drivers can have additional sections.
However, all network drivers must have a configure section, and because
network device drivers are associated with some device, they also must have
a device register header file.
Network Device Driver Environment 1–1

Figure 1–1: Sections of a Network Device Driver
/* Include Files Section */
/* Configure Section */
/* Autoconfiguration Support Section */
/* Start Transmit Section */
Network Device Driver
/* Declarations Section */
/* Initialization Section */
/* Ioctl Section */
/* Interrupt Section */
/* Reset Section */
/* Watchdog Section */
ZK-0818U-AI
Unlike for block and character drivers, you do not specify network driver
entry points in the dsent data structure. This means that a network
driver has no exposure into the file system and, therefore, has no entry in
the /dev directory. Thus, network drivers do not have block and character
driver-specific interfaces such as open,close,read,write, and strategy.
1–2Network Device Driver Environment