请问一个IO端口映射的问题！！！

dengcainiao

以下问题均是指X86平台
    我在看LDD3时了解到外设的内存和端口都可以映射到RAM的地址空间。如果没理解错外设的端口应该用void *ioport_map(unsiged long port,unsigned int count)映射的到AM地址空间，而外设内存应用struct resource *request_mem_region(unsigned long start,unsigned long len,char* name)。我看了一下源代码，ioport-map只是把外设端口+128K这样来完成映射，因此当使用ioread8这样的函数时可以判断出是IO端口还是IO内存以分别使用不同的指令。后观察LDD3中short模块的源码，发现在映射IO端口时用的是request-mem-region而不是ioport_map，一直搞不清楚这样是否会有问题？

seawolf1979

看看这一段：

9.4.3. Ports as I/O Memory
Some hardware has an interesting feature: some versions use I/O ports, while others use I/O memory. The registers exported to the processor are the same in either case, but the access method is different. As a way of making life easier for drivers dealing with this kind of hardware, and as a way of minimizing the apparent differences between I/O port and memory accesses, the 2.6 kernel provides a function called ioport_map:

void *ioport_map(unsigned long port, unsigned int count);


This function remaps count I/O ports and makes them appear to be I/O memory. From that point thereafter, the driver may use ioread8 and friends on the returned addresses and forget that it is using I/O ports at all.

This mapping should be undone when it is no longer needed:

void ioport_unmap(void *addr);


These functions make I/O ports look like memory. Do note, however, that the I/O ports must still be allocated with request_region before they can be remapped in this way.

dengcainiao

可能是我对这段代码理解有误：
if (!use_mem) {
                if (! request_region(short_base, SHORT_NR_PORTS, "short")) {
                        printk(KERN_INFO "short: can't get I/O port address 0x%lx\n",
                                        short_base);
                        return -ENODEV;
                }

        } else {
                if (! request_mem_region(short_base, SHORT_NR_PORTS, "short")) {
                        printk(KERN_INFO "short: can't get I/O mem address 0x%lx\n",
                                        short_base);
                        return -ENODEV;
                }

                /* also, ioremap it */
                short_base = (unsigned long) ioremap(short_base, SHORT_NR_PORTS);
                                //这里我认为应该用ioport_map
                /* Hmm... we should check the return value */
        }