So I understand that a kernel driver sits on top of HW device and then to communicate with the device via user space you will need to talk to the kernel driver via CreateFile && Read && Write. I have seen the design of Window's kernel drivers and their sample codes whether it is a USB or PCI or...
Now what I want to understand is how does the kernel drive communicate with the hardware? Where is the driver code would we usually find the code responsible for reading/writing registers on a certain device? What does the driver need to communicate with the device? I was told it is the BAR0 value that maps the HW to the virtual memory area which means any address we want to access on a physical device would start at that address. Is that correct? what If I have BAR0 = 0xfc500000, do i have to find addresses of certain register on the device and then ad it as an offset?