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

Block I/O Queues

All storage drivers maintain a block I/O queue to house any pending block-centric I/O requests. Generally speaking, these requests are stored in increasing or decreasing device-offset order so that when they are processed, the disk head will move in a single direction (instead of bouncing around) to maximize performance.

The FreeBSD kernel provides the following functions for working with block I/O queues:

#include <sys/bio.h> void bioq_init(struct bio_queue_head *head); void bioq_disksort(struct bio_queue_head *head, struct bio *bp); struct bio * bioq_first(struct bio_queue_head *head); struct bio * bioq_takefirst(struct bio_queue_head *head); void bioq_insert_head(struct bio_queue_head *head, struct bio *bp); void bioq_insert_tail(struct ...