32.3 EFI System Partition

A device manufacturer that produces UEFI Drivers for their devices may choose to have their UEFI Drivers installed onto an EFI System Partition on a target platform. This method may be selected for UEFI Drivers that cannot be distributed using the two methods described above. It may also be a convenient method for UEFI Driver updates to be distributed and installed onto target platforms. See the UEFI Specification for details on EFI System Partitions and http://www.uefi.org for details on how device manufacturers can reserve a subdirectory name for use on EFI System Partitions.

Note: There is no requirement for UEFI conformant platform firmware implementations to load UEFI Drivers from EFI System Partitions. The capability is defined by the UEFI Specification but there is no requirement that all platforms implement this capability.

Since this method depends on being able to access the EFI System Partition, the UEFI Driver that is to be installed on the EFI System Partition must not be required to access the EFI System Partition itself, either directly or indirectly. For example, a UEFI Driver for a SCSI Host Controller cannot be installed on an EFI System Partition of a mass storage device attached to that same SCSI Host Controller. However, if the SCSI Host Controller is a PCI add-in card with a UEFI Driver in a PCI Option ROM or the UEFI Driver for the SCSI Host Controller is integrated in the platform firmware, it may be possible to install an update to the UEFI Driver for the SCSI Host Controller in an EFI System Partition on one of the mass storage devices attached to that SCSI Host Controller as long as the UEFI Driver in the PCI Option ROM or the platform firmware is functional enough to load the updated UEFI Driver from the EFI System Partition.

There are a few steps that must be performed in order for a UEFI Driver to be installed onto an EFI System Partition and for that UEFI Driver to be automatically loaded and executed each time the target platform is booted.

  1. The UEFI Driver must be copied onto a mass storage device that contains an EFI System Partition. This may require a custom UEFI Application to perform this transfer, or utilities such as 1 the UEFI Shell and UEFI Shell scripts may be used to install a UEFI Driver into a device specific directory.

  2. Update the Driver#### and DriverOrder UEFI variables so the UEFI Driver installed on the EFI System Partition is automatically loaded and executed on every boot. These variables can be updated from a custom UEFI Application, or OEM setup screens if this option is exposed.

Tip: Use the UEFI Shell drivers command to view the set of UEFI Drivers that have been loaded and executed to verify that a UEFI Driver that has been installed and configured to load from EFI System Partition has actually been loaded and executed by the platform firmware.