For driver problems, ioremap and (* (unsginedchar *) virtual_addr = 0xff are used.

For driver problems, ioremap and (* (unsginedchar *) virtual_addr0xff are used to assign values-general Linux technology-Linux programming and kernel information. For details, refer to the following. The source code looks like this:
The platform is ARM9.
Virtual_addr = ioremap (phy_addr, 1); virtual_addr is a peripheral Register address in two bytes;
* (Unsigned int *) virtual_addr = 0 xffff;
The program encountered a problem and an error occurred.
What are the errors in this operation ?? Is it related to the second parameter 1 in ioremap? I found that this parameter refers to the number of resources, but I don't understand what is going on.
By the way, functions such as outb, outw, inb, and inw can be used. I personally think this type of function is added to linux to support single- ing between I/O port space and memory space. To put it bluntly, it is the in and out commands under x86, therefore, it is unavailable on the ARM platform. I also encountered a problem when using it. I don't know. Is that true?