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D
evice Driver Programming
17-26
For an I/O device that performs programmed I/O or a user-level device driver that does
intermediate buffer copying, the user-level driver does not need to use physical addresses
to describe the user’s I/O buffer. In such cases, the I/O routines of user-level drivers
written by Concurrent Computer Corporation personnel are still required to accept a
udbuf_t structure to describe the I/O buffer; however, only the virtual address portion of
the structure is used. Other user-level device drivers are not required to use the udbuf_t
structure in such cases.
The aread and awrite routines allow an application to indicate whether or not the
status of an I/O operation is important. When the application asks for status information, it
must check the status of the I/O operation until the I/O completion status is returned. The
writer of a user-level driver must maintain status for aread or awrite operations until
the I/O completion status is returned. If the application indicates that status information is
not important, the user-level driver should discard status or allow it to be overwritten as
soon as the I/O operation is complete.
The asynchronous I/O support routines include aread, awrite, acheck, and await.
They are described in the sections that follow.
The aread Routine 17
The driver’s aread routine allows a user process to perform an asynchronous read of data
from a particular device.
Specification
int xx
_aread(
dev_desc
,
buff_desc
,
count
,
req_id)
int dev_desc
;
udbuf_t *buff_desc
;
int count
;
int *req_id
;
Parameters
dev_desc the identifier for the device from which data are to be read. This identifier is
returned by the driver’s open routine.
buff_desc a pointer to the user I/O buffer that describes the physical locations into which
data are to be read
count the number of bytes to be read
req_id a pointer to the location to which the request identifier of the asynchronous
read operation is returned. The user process can use this identifier to obtain the
status of the operation. If req_id contains a null pointer, information about the
status of the request is not maintained. If req_id contains a pointer, the user-
level driver provides an identifier that the application must use to check the
status of the read request. (See “The acheck Routine” on page 17-28 and “The
await Routine” on page 17-29 for an explanation of the acheck and await
user-level driver routines. These routines can be supplied to allow users to
check the status of an asynchronous I/O request.)
- Device Driver Programming 1
- Syntax Notation 4
- Referenced Publications 4
- Contents 7
- Introduction 17
- Organization of Manual 1 20
- Supporting Documentation 1 21
- Understanding Device Drivers 23
- Structure 2 26
- Parallel Execution 2 27
- Interrupts 2 27
- Types of Devices 2 29
- STREAMS Interface 2 30
- Major and Minor Numbers 2 31
- Driver Environment 2 34
- • Master 35
- • System 35
- Master File 2 35
- Driver Development 2 36
- The PCI Environment 37
- Big Vs Little Endian Issues 3 40
- Types of PCI Resources 3 41
- Base Address Registers(BAR) 3 42
- PowerMax OS Support 3 43
- System Overview 4 49
- Caches 4 50
- Memory 4 51
- Data Types 4 51
- (H)VME Addressing 4 52
- Transfer Width Support 4 53
- Address Types 4 53
- Address Modifiers 4 53
- HVME Address Ranges 4 54
- VME Address Ranges 4 54
- Bus Time-Out 4 56
- Bus Arbitration 4 57
- • Straight priority 58
- • CPU Release on Request 58
- Interrupt Lines (Levels) 4 59
- • jumpers or switches 60
- System Overview 5 65
- Caches 5 66
- Memory 5 67
- Timers 5 67
- Interrupts 5 67
- Data Types 5 68
- Byte-Ordering and Alignment 5 68
- VME Addressing 5 69
- Address Modifiers 5 70
- VME Address Ranges 5 70
- Bus Time-Out 5 71
- • Invalid transfer 72
- Bus Arbitration 5 73
- Interrupt Lines (Levels) 5 74
- VME to PCI Address Decode 5 76
- System Overview 6 79
- Caches 6 80
- Memory 6 81
- Data Types 6 81
- VME Addressing 6 82
- Transfer Width Support 6 83
- Address Types 6 83
- Address Modifiers 6 83
- VME Address Ranges 6 83
- VME Devices as Bus Masters 6 84
- Bus Time-Out 6 85
- Bus Arbitration 6 87
- Interrupt Lines (Levels) 6 88
- System Overview 7 93
- Processor Board 7 96
- Memory 7 96
- Timers 7 97
- Interrupts 7 97
- Data Types 7 97
- Byte-Ordering and Alignment 7 98
- VME Addressing 7 99
- VME Address Ranges 7 100
- Bus Time-Out 7 101
- Bus Arbitration 7 102
- Bus Request Levels 7 103
- Interrupt Lines (Levels) 7 103
- PCI Address Decode 7 105
- 0xC0000000 106
- 0xFCC00000 106
- 0xFCFF0000 106
- 0x80000000 106
- 0xA0000000 106
- SYSTEM OVERVIEW 8 109
- PROCESSOR BOARD 8 109
- MEMORY 8 110
- BUSSES 8 112
- TIMERS 8 112
- INTERRUPTS 8 112
- DATA TYPES 8 113
- BYTE-ORDERING AND ALIGNMENT 8 113
- System Data Structures 9 123
- Header Files 9 124
- The cdevsw Structure 9 125
- The cred Structure 9 127
- The adapter Structure 9 129
- Kernel Support Routines 9 132
- BREAK signal.) 133
- Memory Access Routines 9 135
- Address Management Routines 9 135
- Data Transfer Routines 9 136
- Synchronization Routines 9 137
- Sleep Locks 9 138
- Timing and Timeout Routines 9 139
- Interrupt Vector Routines 9 140
- Debug Routines 9 141
- Developing a Device Driver 145
- Device Registers 10 148
- Command Sequences 10 148
- DMA Support 10 148
- Programmed I/O Support 10 149
- Data Chaining Support 10 149
- Installing the Device 10 150
- Initialization Routines 10 153
- I/O Service Routines 10 153
- Interrupt Service Routines 10 153
- The Init Routine 10 155
- The Open Routine 10 157
- • Enable device interrupts 158
- • Lock a non-sharable device 158
- The Close Routine 10 159
- The Read Routine 10 160
- /* number of bytes to copy */ 161
- The Write Routine 10 162
- The Ioctl Routine 10 163
- The Chpoll Routine 10 164
- • 0 if the poll is successful 164
- The Mmap Routine 10 165
- Local Routines 10 168
- Error Handling 10 169
- Protecting a Device Driver 11 175
- • Global variables 176
- • Hardware registers 176
- • _LOCKTEST 178
- • _MPSTAT 178
- Spin Locks 11 179
- Basic Locks 11 180
- NULL pointer 181
- Read/Write Locks 11 183
- Sleep Locks 11 187
- LWP that suc 191
- Using Multiple Locks 11 192
- Synchronization Variables 11 192
- LWP upon 194
- LWP which is in 194
- LWP goes to sleep. No spin 194
- LWPs are sleeping on 196
- LWPswake 196
- Overview 12 199
- DMA into User Buffers 12 199
- 24-Bit DMA Devices 12 203
- Loadable Modules 205
- The DLM Mechanism 13 208
- Demand Load 13 209
- Auto Load 13 209
- Demand Unload 13 210
- Auto Unload 13 210
- Making Modules Loadable 13 211
- Wrapper Data Structures 13 212
- Wrapper Macros 13 212
- Sample Wrapper Code 13 213
- Managing Loadable Modules 13 218
- Unloading the Module 13 220
- DLM Error Messages 13 220
- Dynamic Symbols and kdb 13 220
- Using idtools 14 223
- Overview of DSP Components 14 229
- DSP Component Files 14 230
- Driver.o 14 231
- Master 14 231
- System 14 231
- $version 1 232
- $loadable gt 232
- Mtune 14 233
- Sassign 14 235
- Space.c 14 236
- Packaging the Driver 14 237
- Installing a Package 14 240
- Removing a Package 14 241
- Installing a DSP 14 241
- Updating a DSP 14 242
- Removing a DSP 14 242
- Building a New Kernel 14 243
- Driver Testing and Debugging 245
- General Guidelines 15 248
- Common Driver Problems 15 251
- Timing Errors 15 252
- Corrupted Interrupt Stack 15 252
- Accessing Critical Data 15 252
- Booting Scenarios 15 255
- Shutdown and Reboot 15 255
- Using crash Functions 15 263
- Kernel Debugger 15 264
- Entering kdb from a Driver 15 265
- System Panics 15 265
- Special Considerations 267
- Additional Considerations 16 272
- System Requirements 16 272
- P_PLOCK 278
- Shared Memory Regions 17 282
- User I/O Buffer Descriptor 17 283
- Overview of Error Returns 17 289
- Driver 17 291
- The spl Support Routines 17 295
- Rescheduling Control Tools 17 296
- The Server System Calls 17 297
- The open Routine 17 299
- The aread Routine 17 302
- The awrite Routine 17 303
- The acheck Routine 17 304
- The await Routine 17 305
- Control Functions 17 306
- The close Routine 17 307
- Use of Local Memory 17 312
- MPA_CPU_VMELEV command; 313
- P_SHMBIND 315
- Reset the Device 17 316
- Debugging the Driver 17 317
- Glossary 325
- Glossary-12 336
- I/O 10-7 338
- STREAMS interface 2-6 338
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