ABOUT THE AUTHOR AND THE TECHNICAL REVIEWER. Who Is This Book For?...xxiii Prerequisites...xxiv Contents at a Glance...xxiv Welcome Aboard!...

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2 CONTENTS IN DETAIL ABOUT THE AUTHOR AND THE TECHNICAL REVIEWER xvii FOREWORD by John Baldwin xix ACKNOWLEDGMENTS xxi INTRODUCTION xxiii Who Is This Book For?...xxiii Prerequisites...xxiv Contents at a Glance...xxiv Welcome Aboard!...xxv 1 BUILDING AND RUNNING MODULES 1 Types of Device Drivers... 1 Loadable Kernel Modules... 2 Module Event Handler... 2 DECLARE_MODULE Macro... 3 Hello, world!... 5 Compiling and Loading... 6 Character Drivers... 7 d_foo Functions... 7 Character Device Switch Table... 8 make_dev and destroy_dev Functions... 9 Mostly Harmless echo_write Function echo_read Function echo_modevent Function DEV_MODULE Macro Don t Panic Block Drivers Are Gone Conclusion ALLOCATING MEMORY 17 Memory Management Routines malloc_type Structures MALLOC_DEFINE Macro MALLOC_DECLARE Macro... 20

3 Tying Everything Together Contiguous Physical Memory Management Routines A Straightforward Example Conclusion DEVICE COMMUNICATION AND CONTROL 27 ioctl Defining ioctl Commands Implementing ioctl echo_write Function echo_set_buffer_size Function echo_ioctl Function echo_modevent Function Don t Panic Invoking ioctl sysctl Implementing sysctls, Part sysctl Context Management Routines Creating Dynamic sysctls SYSCTL_STATIC_CHILDREN Macro SYSCTL_CHILDREN Macro Implementing sysctls, Part sysctl_set_buffer_size Function Don t Panic Conclusion THREAD SYNCHRONIZATION 53 A Simple Synchronization Problem A More Complex Synchronization Problem race_new Function race_find Function race_destroy Function race_ioctl Function race_modevent Function The Root of the Problem Preventing Race Conditions Mutexes Spin Mutexes Sleep Mutexes Mutex Management Routines Implementing Mutexes race_modevent Function Don t Panic Shared/Exclusive Locks Shared/Exclusive Lock Management Routines Implementing Shared/Exclusive Locks Reader/Writer Locks Reader/Writer Lock Management Routines x

4 Condition Variables Condition Variable Management Routines General Guidelines Avoid Recursing on Exclusive Locks Avoid Holding Exclusive Locks for Long Periods of Time Conclusion DELAYING EXECUTION 83 Voluntary Context Switching, or Sleeping Implementing Sleeps and Condition Variables sleep_modevent Function load Function sleep_thread Function sysctl_debug_sleep_test Function unload Function Don t Panic Kernel Event Handlers Callouts Callouts and Race Conditions Taskqueues Global Taskqueues Taskqueue Management Routines Conclusion CASE STUDY: VIRTUAL NULL MODEM 99 Prerequisites Code Analysis nmdm_modevent Function nmdm_clone Function nmdm_alloc Function nmdm_outwakeup Function nmdm_task_tty Function nmdm_inwakeup Function nmdm_modem Function nmdm_param Function nmdm_timeout Function bits_per_char Function Don t Panic Conclusion NEWBUS AND RESOURCE ALLOCATION 113 Autoconfiguration and Newbus Drivers device_foo Functions Device Method Table DRIVER_MODULE Macro xi

5 Tying Everything Together foo_pci_probe Function foo_pci_attach Function d_foo Functions foo_pci_detach Function Don t Panic Hardware Resource Management Conclusion INTERRUPT HANDLING 125 Registering an Interrupt Handler Interrupt Handlers in FreeBSD Implementing an Interrupt Handler pint_identify Function pint_probe Function pint_attach Function pint_detach Function pint_open Function pint_close Function pint_write Function pint_read Function pint_intr Function Don t Panic Generating Interrupts on the Parallel Port Conclusion CASE STUDY: PARALLEL PORT PRINTER DRIVER 141 Code Analysis lpt_identify Function lpt_probe Function lpt_detect Function lpt_port_test Function lpt_attach Function lpt_detach Function lpt_open Function lpt_read Function lpt_write Function lpt_intr Function lpt_timeout Function lpt_push_bytes Function lpt_close Function lpt_ioctl Function lpt_request_ppbus Function lpt_release_ppbus Function Conclusion xii

6 10 MANAGING AND USING RESOURCES 165 I/O Ports and I/O Memory Reading from I/O Ports and I/O Memory Writing to I/O Ports and I/O Memory Stream Operations Memory Barriers Tying Everything Together led_identify Function led_probe Function led_attach Function led_detach Function led_open Function led_close Function led_read Function led_write Function Conclusion CASE STUDY: INTELLIGENT PLATFORM MANAGEMENT INTERFACE DRIVER 183 Code Analysis ipmi_pci_probe Function ipmi_pci_match Function ipmi_pci_attach Function ipmi2_pci_probe Function ipmi2_pci_attach Function Conclusion DIRECT MEMORY ACCESS 193 Implementing DMA Initiating a DMA Data Transfer Dismantling DMA Creating DMA Tags Tearing Down DMA Tags DMA Map Management Routines, Part Loading (DMA) Buffers into DMA Maps bus_dma_segment Structures bus_dmamap_load Function bus_dmamap_load_mbuf Function bus_dmamap_load_mbuf_sg Function bus_dmamap_load_uio Function bus_dmamap_unload Function DMA Map Management Routines, Part A Straightforward Example Synchronizing DMA Buffers Conclusion xiii

7 13 STORAGE DRIVERS 207 disk Structures Descriptive Fields Storage Device Methods Mandatory Media Properties Optional Media Properties Driver Private Data disk Structure Management Routines Block I/O Structures Block I/O Queues Tying Everything Together at45d_attach Function at45d_delayed_attach Function at45d_get_info Function at45d_wait_for_device_ready Function at45d_get_status Function at45d_strategy Function at45d_task Function Block I/O Completion Routines Conclusion COMMON ACCESS METHOD 225 How CAM Works A (Somewhat) Simple Example mfip_attach Function mfip_detach Function mfip_action Function mfip_poll Function mfip_start Function mfip_done Function SIM Registration Routines cam_simq_alloc Function cam_sim_alloc Function xpt_bus_register Function Action Routines XPT_PATH_INQ XPT_RESET_BUS XPT_GET_TRAN_SETTINGS XPT_SET_TRAN_SETTINGS XPT_SCSI_IO XPT_RESET_DEV Conclusion xiv

8 15 USB DRIVERS 257 About USB Devices More About USB Devices USB Configuration Structures Mandatory Fields Optional Fields USB Transfer Flags USB Transfers (in FreeBSD) USB Configuration Structure Management Routines USB Methods Structure Tying Everything Together ulpt_probe Function ulpt_attach Function ulpt_detach Function ulpt_open Function ulpt_reset Function unlpt_open Function ulpt_close Function ulpt_ioctl Function ulpt_watchdog Function ulpt_start_read Function ulpt_stop_read Function ulpt_start_write Function ulpt_stop_write Function ulpt_write_callback Function ulpt_read_callback Function ulpt_status_callback Function Conclusion NETWORK DRIVERS, PART 1: DATA STRUCTURES 283 Network Interface Structures Network Interface Structure Management Routines ether_ifattach Function ether_ifdetach Function Network Interface Media Structures Network Interface Media Structure Management Routines Hello, world! mbuf Structures Message Signaled Interrupts Implementing MSI MSI Management Routines Conclusion xv

9 17 NETWORK DRIVERS, PART 2: PACKET RECEPTION AND TRANSMISSION 299 Packet Reception em_rxeof Function em_handle_rx Function Packet Transmission em_start_locked Function em_txeof Function Post Packet Transmission Conclusion REFERENCES 309 INDEX 311 xvi