book

FreeBSD Device Drivers

by Joseph Kong

April 2012

Intermediate to advanced

352 pages

English

No Starch Press

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Who Is This Book For?
Types of Device Drivers
Module Event HandlerDECLARE_MODULE Macronamedatasuborder

d_foo FunctionsCharacter Device Switch Tablemake_dev and destroy_dev Functions
echo_write Functionecho_read Functionecho_modevent FunctionDEV_MODULE MacroDon’t Panic
Memory Management Routines
MALLOC_DEFINE MacroMALLOC_DECLARE Macro
ioctl
echo_write Functionecho_set_buffer_size Functionecho_ioctl Functionecho_modevent FunctionDon’t Panic
SYSCTL_STATIC_CHILDREN MacroSYSCTL_CHILDREN Macro
sysctl_set_buffer_size FunctionDon’t Panic
A Simple Synchronization Problem
race_new Functionrace_find Functionrace_destroy Functionrace_ioctl Functionrace_modevent FunctionThe Root of the Problem
Spin MutexesSleep Mutexes
race_modevent FunctionDon’t Panic
Avoid Recursing on Exclusive LocksAvoid Holding Exclusive Locks for Long Periods of Time
Voluntary Context Switching, or Sleeping
sleep_modevent Functionload Functionsleep_thread Functionsysctl_debug_sleep_test Functionunload FunctionDon’t Panic
Global TaskqueuesTaskqueue Management Routines
Prerequisites
nmdm_modevent Functionnmdm_clone Functionnmdm_alloc Functionnmdm_outwakeup Functionnmdm_task_tty Functionnmdm_inwakeup Functionnmdm_modem Functionnmdm_param Functionnmdm_timeout Functionbits_per_char FunctionDon’t Panic
Autoconfiguration and Newbus Driversdevice_foo FunctionsDevice Method TableDRIVER_MODULE Macronamebusnamedriverdevclassevharg
foo_pci_probe Functionfoo_pci_attach Functiond_foo Functionsfoo_pci_detach FunctionDon’t Panic
Registering an Interrupt Handler
pint_identify Functionpint_probe Functionpint_attach Functionpint_detach Functionpint_open Functionpint_close Functionpint_write Functionpint_read Functionpint_intr FunctionDon’t Panic
Code Analysislpt_identify Functionlpt_probe Functionlpt_detect Functionlpt_port_test Functionlpt_attach Functionlpt_detach Functionlpt_open Functionlpt_read Functionlpt_write Functionlpt_intr Functionlpt_timeout Functionlpt_push_bytes Functionlpt_close Functionlpt_ioctl Functionlpt_request_ppbus Functionlpt_release_ppbus Function
I/O Ports and I/O MemoryReading from I/O Ports and I/O MemoryWriting to I/O Ports and I/O MemoryStream Operations
led_identify Functionled_probe Functionled_attach Functionled_detach Functionled_open Functionled_close Functionled_read Functionled_write Function
Code Analysisipmi_pci_probe Functionipmi_pci_match Functionipmi_pci_attach Functionipmi2_pci_probe Functionipmi2_pci_attach Function
Implementing DMAInitiating a DMA Data TransferDismantling DMA
bus_dma_segment Structuresbus_dmamap_load Functionbus_dmamap_load_mbuf Functionbus_dmamap_load_mbuf_sg Functionbus_dmamap_load_uio Functionbus_dmamap_unload Function
disk StructuresDescriptive FieldsStorage Device MethodsMandatory Media PropertiesOptional Media PropertiesDriver Private Data
at45d_attach Functionat45d_delayed_attach Functionat45d_get_info Functionat45d_wait_for_device_ready Functionat45d_get_status Functionat45d_strategy Functionat45d_task Function
How CAM Works
mfip_attach Functionmfip_detach Functionmfip_action Functionmfip_poll Functionmfip_start Functionmfip_done Function
cam_simq_alloc Functioncam_sim_alloc Functionxpt_bus_register Function
XPT_PATH_INQXPT_RESET_BUSXPT_GET_TRAN_SETTINGSXPT_SET_TRAN_SETTINGSXPT_SCSI_IOXPT_RESET_DEV
About USB Devices
Mandatory FieldsOptional FieldsUSB Transfer Flags
ulpt_probe Functionulpt_attach Functionulpt_detach Functionulpt_open Functionulpt_reset Functionunlpt_open Functionulpt_close Functionulpt_ioctl Functionulpt_watchdog Functionulpt_start_read Functionulpt_stop_read Functionulpt_start_write Functionulpt_stop_write Functionulpt_write_callback Functionulpt_read_callback Functionulpt_status_callback Function
Network Interface Structures
ether_ifattach Functionether_ifdetach Function
Packet Receptionem_rxeof Functionem_handle_rx Function
em_start_locked Functionem_txeof Function

Content preview from FreeBSD Device Drivers

Chapter 6. Case Study: Virtual Null Modem

This chapter is the first of several case studies that’ll guide you through a real-world device driver. The purpose of these case studies is to expose you to genuine driver code—warts and all—and to consolidate the information presented in earlier chapters.

In this chapter, we’ll go through nmdm(4), the virtual null modem terminal driver. This driver creates two tty(4) devices that are connected by a virtual null modem cable. In other words, the output of one tty(4) device is the input for the other tty(4) device, and vice versa. I chose to profile nmdm(4) because it uses event handlers, callouts, and taskqueues, ...