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Writing Device Drivers     Oracle Solaris 11 Information Library
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Part I Designing Device Drivers for the Oracle Solaris Platform

1.  Overview of Oracle Solaris Device Drivers

2.  Oracle Solaris Kernel and Device Tree

3.  Multithreading

4.  Properties

5.  Managing Events and Queueing Tasks

6.  Driver Autoconfiguration

7.  Device Access: Programmed I/O

8.  Interrupt Handlers

9.  Direct Memory Access (DMA)

10.  Mapping Device and Kernel Memory

11.  Device Context Management

12.  Power Management

13.  Hardening Oracle Solaris Drivers

14.  Layered Driver Interface (LDI)

Part II Designing Specific Kinds of Device Drivers

15.  Drivers for Character Devices

Overview of the Character Driver Structure

Character Device Autoconfiguration

Device Access (Character Drivers)

open() Entry Point (Character Drivers)

close() Entry Point (Character Drivers)

I/O Request Handling

User Addresses

Vectored I/O

Differences Between Synchronous and Asynchronous I/O

Data Transfer Methods

Programmed I/O Transfers

DMA Transfers (Synchronous)

DMA Transfers (Asynchronous)

minphys() Entry Point

strategy() Entry Point

Mapping Device Memory

Multiplexing I/O on File Descriptors

Miscellaneous I/O Control

ioctl() Entry Point (Character Drivers)

I/O Control Support for 64-Bit Capable Device Drivers

Handling copyout() Overflow

32-bit and 64-bit Data Structure Macros

How Do the Structure Macros Work?

When to Use Structure Macros

Declaring and Initializing Structure Handles

Operations on Structure Handles

Other Operations

16.  Drivers for Block Devices

17.  SCSI Target Drivers

18.  SCSI Host Bus Adapter Drivers

19.  Drivers for Network Devices

20.  USB Drivers

21.  SR-IOV Drivers

Part III Building a Device Driver

22.  Compiling, Loading, Packaging, and Testing Drivers

23.  Debugging, Testing, and Tuning Device Drivers

24.  Recommended Coding Practices

Part IV Appendixes

A.  Hardware Overview

B.  Summary of Oracle Solaris DDI/DKI Services

C.  Making a Device Driver 64-Bit Ready

D.  Console Frame Buffer Drivers

E.  pci.conf File


Multiplexing I/O on File Descriptors

A thread sometimes needs to handle I/O on more than one file descriptor. One example is an application program that needs to read the temperature from a temperature-sensing device and then report the temperature to an interactive display. A program that makes a read request with no data available should not block while waiting for the temperature before interacting with the user again.

The poll(2) system call provides users with a mechanism for multiplexing I/O over a set of file descriptors that reference open files. poll(2) identifies those file descriptors on which a program can send or receive data without blocking, or on which certain events have occurred.

To enable a program to poll a character driver, the driver must implement the chpoll(9E) entry point. The system calls chpoll(9E) when a user process issues a poll(2) system call on a file descriptor associated with the device. The chpoll(9E) entry point routine is used by non-STREAMS character device drivers that need to support polling.

The chpoll(9E) function uses the following syntax:

int xxchpoll(dev_t dev, short events, int anyyet, short *reventsp,
     struct pollhead **phpp);

In the chpoll(9E) entry point, the driver must follow these rules:

Example 15-10 and Example 15-11 show how to implement the polling discipline and how to use pollwakeup(9F).

The following example shows how to handle the POLLIN and POLLERR events. The driver first reads the status register to determine the current state of the device. The parameter events specifies which conditions the driver should check. If an appropriate condition has occurred, the driver sets that bit in *reventsp. If none of the conditions has occurred and if anyyet is not set, the address of the pollhead structure is returned in *phpp.

Example 15-10 chpoll(9E) Routine

static int
xxchpoll(dev_t dev, short events, int anyyet,
    short *reventsp, struct pollhead **phpp)
     uint8_t status;
     short revent;
     struct xxstate *xsp;

     xsp = ddi_get_soft_state(statep, getminor(dev));
     if (xsp == NULL)
         return (ENXIO);
     revent = 0;
      * Valid events are:
      * This example checks only for POLLIN and POLLERR.
     status = ddi_get8(xsp->data_access_handle, &xsp->regp->csr);
     if ((events & POLLIN) && data available to read) {
        revent |= POLLIN;
     if (status & DEVICE_ERROR) {
        revent |= POLLERR;
     /* if nothing has occurred */
     if (revent == 0) {
        if (!anyyet) {
        *phpp = &xsp->pollhead;
       *reventsp = revent;
     return (0);

The following example shows how to use the pollwakeup(9F) function. The pollwakeup(9F) function usually is called in the interrupt routine when a supported condition has occurred. The interrupt routine reads the status from the status register and checks for the conditions. The routine then calls pollwakeup(9F) for each event to possibly notify polling threads that they should check again. Note that pollwakeup(9F) should not be called with any locks held, since deadlock could result if another routine tried to enter chpoll(9E) and grab the same lock.

Example 15-11 Interrupt Routine Supporting chpoll(9E)

static u_int
xxintr(caddr_t arg)
     struct xxstate *xsp = (struct xxstate *)arg;
     uint8_t    status;
     /* normal interrupt processing */
     /* ... */
     status = ddi_get8(xsp->data_access_handle, &xsp->regp->csr);
     if (status & DEVICE_ERROR) {
        pollwakeup(&xsp->pollhead, POLLERR);
     if ( /* just completed a read */ ) {
        pollwakeup(&xsp->pollhead, POLLIN);
     /* ... */
     return (DDI_INTR_CLAIMED);