Trait chipset_device::pci::PciConfigSpace
source · pub trait PciConfigSpace: ChipsetDevice {
// Required methods
fn pci_cfg_read(&mut self, offset: u16, value: &mut u32) -> IoResult;
fn pci_cfg_write(&mut self, offset: u16, value: u32) -> IoResult;
// Provided method
fn suggested_bdf(&mut self) -> Option<(u8, u8, u8)> { ... }
}
Expand description
Implemented by devices which have a PCI config space.
Required Methods§
sourcefn pci_cfg_read(&mut self, offset: u16, value: &mut u32) -> IoResult
fn pci_cfg_read(&mut self, offset: u16, value: &mut u32) -> IoResult
Dispatch a PCI config space read to the device with the given address.
sourcefn pci_cfg_write(&mut self, offset: u16, value: u32) -> IoResult
fn pci_cfg_write(&mut self, offset: u16, value: u32) -> IoResult
Dispatch a PCI config space write to the device with the given address.
Provided Methods§
sourcefn suggested_bdf(&mut self) -> Option<(u8, u8, u8)>
fn suggested_bdf(&mut self) -> Option<(u8, u8, u8)>
Check if the device has a suggested (bus, device, function) it expects to be located at.
The term “suggested” is important here, as it’s important to note that one of the major selling points of PCI was that PCI devices shouldn’t need to care about about what PCI address they are initialized at. i.e: on a physical machine, it shouldn’t matter that your fancy GTX 4090 is plugged into the first vs. second PCI slot.
..that said, there are some instances where it makes sense for an emulated device to declare its suggested PCI address:
- Devices that emulate bespoke PCI devices part of a particular system’s chipset.
- e.g: the PIIX4 chipset includes several bespoke PCI devices that are required to have specific PCI addresses. While it would be possible to relocate them to a different address, it may break OSes that assume they exist at those spec-declared addresses.
- Multi-function PCI devices
- In an unfortunate case of inverted responsibilities, there is a
single bit in the PCI configuration space’s
Header
register that denotes if a particular PCI card includes multiple functions. - Since multi-function devices are pretty rare,
ChipsetDevice
opted to model each function as its own device, which in turn implies that in order to correctly init a multi-function PCI card, theChipsetDevice
with function 0 must report if there are other functions at the same bus and device.