18.3.3 PCI Cards with Multiple PCI Controllers
Some PCI devices have a series of identical devices on a single device, normally behind a PCI bridge. These devices may require additional work if they need to be controlled by a single instance of the UEFI driver. Take the following figure as a sample device.
Figure 20-A multi-controller PCI device
It may be required that the driver in the Option ROM control all 3 controllers on the PCI device. To do this, use the following actions:
- In the
Supported()function, make sure that the UEFI Driver supports the controller that is passed into theSupport()function. The first controller passed in could be any of the controllers on a PCI Card. - In the
Supported()function, make sure the function does not touch or change the HW state. This is very important. If the PCI I/O instance is already opened (if some other application or driver is already managing the controller), return an error. See Chapter 9 of this guide and the EFI Driver Binding Protocol section of the UEFI Specification for details on the error return codes from the Driver Binding ProtocolSupported()function. - In the
Start()function for the first controller on the PCI Card, open the PCI I/O protocol instances on the other handles on the same PCI Card using theEFI_OPEN_PROTOCOL_BY_DRIVERattribute. This informs all other UEFI Drivers in the platform that all the controllers on the PCI Card are already being managed. To scan for other PCI controllers on the same PCI Card, use the UEFI Boot Service LocateHandleBuffer() to find all handles in the Handle Database supporting the PCI I/O Protocol. Use the PCI I/O Protocol function GetLocation()to evaluate whether or not the PCI controller is on the same PCI bus number. Take care to not modify the HW state of any PCI I/O Protocol instance during this evaluation. - In the
Stop()function, undo everything that was done inStart(). Use a private context data structure to keep track of the information required to complete aStop()operation in these more complex use cases.