Clarification regarding PCI device initialization

Question

Wikipedia says:

To address a PCI device, it must be enabled by being mapped into the system's I/O port address space or memory-mapped address space. The system's firmware, device drivers or the operating system program the Base Address Registers (commonly called BARs) to inform the device of its address mapping by writing configuration commands to the PCI controller.

Does this mean that a PCI device gets initialized when an address is written to the BAR? I'm trying to initialize the Bochs VGA card on Qemu Aarch64 thru bare metal and that's why I'm asking. Thanks!

Answer 1

Writing to the BAR simply tells the device what address range it should respond to. (It doesn't even enable the device to respond to the address; for that you need to set MSE [memory space enable].) There are many steps typically needed to initialize a device. Some of the steps are common for different PCI devices and others are completely device specific.