enum vga_switcheroo_client_id — client identifier
enum vga_switcheroo_client_id { VGA_SWITCHEROO_UNKNOWN_ID, VGA_SWITCHEROO_IGD, VGA_SWITCHEROO_DIS, VGA_SWITCHEROO_MAX_CLIENTS };
initial identifier assigned to vga clients.
Determining the id requires the handler, so GPUs are given their
true id in a delayed fashion in vga_switcheroo_enable
integrated graphics device
discrete graphics device
currently no more than two GPUs are supported