Linux下读写I/O port

1. 基础知识：


1．1 在存取任何 I/O port之前,必??程式有如此做的?限. 要?成??目的你可以在你的程式一?始的地方 (但是要在任何 I/O port存取?作之前) 呼叫 ioperm() ??函数 (?函数被声明於?案 /usr/include/sys/io.h).

使用?法是:

ioperm(from, num, turn_on)

其中 from 是第一?允?存取的 I/O port位址;num 是接著??存取 I/O port位址的?目. 例如, ioperm(0x300, 5, 1) 的意思就是?允?存取port 0x300 到 0x304 (一共五?port位址). 而最後一???是一?布尔值用?指定是否?予程式存取 I/O port的?限 (true (1)) 或是除去存取的?限 (false (0)).

函数 ioperm() 只能?你取得Port位址 0x000 到 0x3ff 的存取?限; 至於?高位址的Port, 你得使用函数 iopl() (?函数?你一次可以存取所有的Port位址). ??限等???值?? 3 (例如, iopl(3)) 以便你的程式能?存取 所有的 I/O Port。


1．2 获得读取权限后，就可以对I/O port进行读写了。

a．读

要?某?Port地址读取一? byte (8 ? bits) 的?料, 可以调用函数 inb(port)；类似的有：


inw (port) //读取 2 个 bytes


inl (port) //读取 4 个bytes


b．写

要向某?Port地址写入一? byte (8 ? bits) 的?料,调用函数 outb(value, port)；类似的有：

outw(value, port)

outl(value, port)

2. 应用实列：
2．1 源程序：

/* name: pci.c */
#include
#include
#include

#define IO_PORTS1 1 /* ioport <= 0x3ff */
#define IO_PORTS2 2 /* ioport >0x3ff && ioport < 0xffff */
#define IO_PERMOFF 0
#define IO_PERMON 1
#define IO_PERMON2 3

#define RW_DELAY 10000 /*delay 100000 microseconds for reading and writing I/O ports. */
#ifndef BOOL
typedef unsigned char BOOL;
#endif

#ifndef BYTE
typedef unsigned char BYTE;
#endif

#ifndef DWORD
typedef unsigned long DWORD;
#endif

#ifndef INT
typedef unsigned int INT;
#endif

#ifndef ULONG
typedef unsigned long ULONG;
#endif

#ifndef WORD
typedef unsigned short WORD;
#endif
/*
** Function : Write the value of the specified I/O port by giving the length and the
** starting address.
** Parameter: PortAddr: the port address
** PortVal : the value to set
** size : size = 1 for reading 1 byte, 2 for word, 4 for double words
** Return : 1 returned if success, or 0 returned
*/
BOOL SetPortVal(WORD PortAddr, DWORD PortVal, BYTE size)
{
BOOL Ret = 0;
INT tmpRet = 0;
ULONG numperm = 1;
INT privilege = 0;
assert(PortAddr>0);
if(PortAddr <=0x3ff)
{
tmpRet = ioperm((ULONG)PortAddr, numperm, IO_PERMON);
privilege = IO_PORTS1;
}
else if( PortAddr > 0x3ff
{
tmpRet = iopl(IO_PERMON2);
privilege = IO_PORTS2;
}
else
return Ret;
if(tmpRet<0)
{
fprintf(stderr, "can't set the io port permission for setting !\n";
return Ret;
}
else
{
switch(size)
{
case 1: /*write one byte to the port */
outb(PortVal, PortAddr);
break;
case 2: /*write one word to the port */
outw(PortVal, PortAddr);
break;
case 4: /*write double words to the port */
outl(PortVal, PortAddr);
break;
default:
Ret = 0;
break;
}
usleep(RW_DELAY);
Ret = 1;
}
if( privilege == IO_PORTS1
ioperm((ULONG)PortAddr, numperm, IO_PERMOFF);
else if(privilege == IO_PORTS2
iopl(IO_PERMOFF);
return Ret;
}

/*
** Function : Read the value of the specified I/O port by giving the lenght and the
** starting address.
** Parameter: PortAddr : the port address
** PortVal : value from port
** size : size = 1 for reading 1 byte, 2 for word, 4 for double words
** Return : 1 returned if success, or 0 returned.
*/
BOOL GetPortVal(WORD PortAddr, DWORD * PortVal, BYTE size)
{
BOOL Ret = 0;
int tmpRet = 0;
unsigned long numperm = 1;
int privilege = 0;
assert(PortAddr>0);
assert(PortVal!=NULL);
if(PortAddr <=0x3ff)
{
tmpRet = ioperm((unsigned long)PortAddr, numperm, IO_PERMON);
privilege = IO_PORTS1;
}
else if( PortAddr > 0x3ff
{
tmpRet = iopl(IO_PERMON2);
privilege = IO_PORTS2;
}
else
return Ret;
if(tmpRet<0)
{
fprintf(stderr, "can't set the io port permission for reading !\n";
return Ret;
}
else
{
switch(size)
{
case 1: /*read one byte from the port */
*PortVal = inb(PortAddr);
break;
case 2: /*read one word from the port */
*PortVal = inw(PortAddr);
break;
case 4: /*read double words from the port */
*PortVal = inl(PortAddr);
break;
default:
Ret = 0;
break;
}
usleep(RW_DELAY);
Ret = 1;
}

if( privilege == IO_PORTS1
ioperm( (unsigned long)PortAddr, numperm, IO_PERMOFF ;
else if( privilege == IO_PORTS2
iopl(IO_PERMOFF);
return Ret;
}

int main (int argc, char * argv[])
{
WORD add_port = 0xcf8;
WORD data_port = 0xcfc;
DWORD addr = 0x80000000;
DWORD port_value;
BYTE size = 4;
int input;
printf("Please select the option number as follow:\n";
printf("1--bus 0:dev:0 fun:0 as address 0x80000000\n";
printf("2--bus 0:dev:1 fun:0 as address 0x80000800\n";
printf("3--input your own defined address value:\n";
scanf("%d",&input);
switch(input)
{
case 1:
addr=0x80000000;
break;
case 2:
addr=0x80000800;
break;
case 3:
printf("please input the 32 bits address in Hex format(such as 80007800): ";
scanf ("%x", &addr);
break;
default:
printf("input invalid option num, exit program.\n";
return -1;
}
printf ("The addr is :%X\n", addr);
printf ("The add_port is : %X\n", add_port);
printf ("The data_port is : %X\n", data_port);
if (SetPortVal(add_port, addr, size))
{
if (GetPortVal(data_port, &port_value, size))
{
printf("port value is :%08X\n", port_value);
return 0;
}
}
return -1;
}

2.2 编译：
gcc -o pci pci.c
gcc 带参数 -o 指定输出的文件名，如不带参数则默认以a.out做为文件名；
如要加入调试信息，则带参数-g，然后用gdb命令进行调试：
gcc -o pci -g pci.c
gdb pci
有关gdb的用法参见相关资料；

2．3 运行：
输入： ./pci （注意: / 前有．表示当前目录下）
可以将结果和系统的pci信息对照，以检查结果是否正确：
more /proc/pci