关于读PCI配置寄存器。

在WRITE_PORT_ULONG(0xcf8,...)之前，有必要KeRaiseIrql吗？为什么？谢谢。

在这里没有这个必要，KeRaiseIrql只为提高优先级，以提供一段不原被打断的处理。WRITE_PORT_ULONG,本身不存在这种事情。另外，你写的0XCF8这个端口地址：如果你在驱动程序中，用它来访问配置空间，显得有些麻烦。配置空间映射后，可使用直接的地址访问，要简便一些。

谢谢众位的的关注：但9054的Driver代码里有这样一段：
    KeRaiseIrql(
        DISPATCH_LEVEL,
        &IrqlSave
        );

    // Save the content of the command register
    RegisterSave = READ_PORT_ULONG(
                       (ULONG*)0xcf8
                       );

    // Scan the PCI bus to find our device
// MAX_PCI_DEV = 32dev)
    for (SlotNumber = 0; SlotNumber < MAX_PCI_DEV;          SlotNumber++)
    {
        // Issue PCI Config write command
        WRITE_PORT_ULONG(
            (ULONG*)0xcf8,
            (1 << 31) | (pdx->Device.BusNumber << 16) | (SlotNumber << 11) | 0x10
            );

        // Get the Result
        if (READ_PORT_ULONG((ULONG*)0xcfc) == RegisterToCompare)
        {
            pdx->Device.SlotNumber = SlotNumber;
            KdPrint((DBG_NAME \"Workaround successful, Slot number = %02Xh\\n\", SlotNumber));
            break;
        }
    }

    // Restore saved command register
    WRITE_PORT_ULONG(
        (ULONG*)0xcf8,
        RegisterSave
        );

    // Restore IRQL
    KeLowerIrql(
        IrqlSave
        );

而且还注解说：
   Scanning the PCI bus involves using  I/O addresses 0xcf8 and  0xcfc. These addresses must be used together and no other process must interrupt, so we must raise the IRQL.
由是为什么？

两个成对使用的寄存器,一次读一次写,如果中间又中断那模你的原有配置不就完蛋了吗?相当于一个原语吧!

To Tom.cat:
            Of course i know the functions of registers CFC and CF8, i have clearly put it in my first post message of the  current thread. CF8 is my most confused spot here, not READ_PORT_ULONG. OK? But anyway i will give u some scores for ur frequent helping. Thx .

To Tom.cat:
            Of course i know the functions of registers CFC and CF8, i have clearly put it in my first post message of the  current thread. CF8 is my most confused spot here, not READ_PORT_ULONG. OK? But anyway i will give u some scores for ur frequent helping. Thx .

To jansen:
     啥叫原语呀？回答完了就给分。

To Tom.cat:
            Of course i know the functions of registers CFC and CF8, i have clearly put it in my first post message of the  current thread. CF8 is my most confused spot here, not READ_PORT_ULONG. OK? But anyway i will give u some scores for ur frequent helping. Thx .

To jansen:
     啥叫原语呀？回答完了就给分。
 

\"原语\"的意思就像是一个原子操作吧！

To Tom.cat:
            Of course i know the functions of registers CFC and CF8, i have clearly put it in my first post message of the  current thread. CF8 is my most confused spot here, not READ_PORT_ULONG. OK? But anyway i will give u some scores for ur frequent helping. Thx .

To jansen:
     啥叫原语呀？回答完了就给分。
 

\"原语\"的意思就像是一个原子操作吧！

补充：请参见操作系统：自旋锁（SPIN_LOCK）...

对不起piig.我吧分加错了，加到tom.cat上去了，你再看见我发贴子，就过来废一句话，我再给你补上，真不好意思。

http://www.driverdevelop.com/read.php?t=A&id=113

I gave the detail reason in the attached article.