[Qemu-devel] Purpose of Cirrus VGA BIOS

[Bartosz Fabianowski]

Hi all

I am trying to figure out how the new Cirrus emulation works. One thing 
I am still not sure about is the purpose of the Cirrus BIOS. The 
emulation coded inside QEMU seems to be trapping the graphics card 
interrupt as well as port and memory accesses. It also performs lots of 
operations and reacts to registers being changed or the interrupt being 
invoked. So, what exactly is the purpose of the graphics card BIOS in 
this scenario? What purpose does it serve? Obviously, a real Cirrus BIOS 
contains lots of code that would control a real Cirrus graphics card and 
that is totally unnecessary in QEMU. What other stuff does it contain 
that can't be done in native C code?

- Bartosz