EFI device paths for block devices must be unique. If a non-unique device
path is discovered, probing of the block device fails.
Currently we use UsbClass() device path nodes. As multiple devices may
have the same vendor and product id these are non-unique. Instead we
should use Usb() device path nodes. They include the USB port on the
parent hub and hence are unique.
A USB storage device may contain multiple logical units. These can be
modeled as Ctrl() nodes.
Given a driver model tree
root 0 root_driver root_driver
usb 0 ehci_generic |-- usb@1c1a000
usb_hub 0 usb_hub `-- usb_hub
usb_hub 1 usb_hub `-- usb_hub
usb_mass_s 2 usb_mass_storage `-- usb_mass_storage
blk 4 usb_storage_blk |-- usb_mass_storage.lun0
where the USB mass storage device is connected to port 4 of the 2nd hub,
the device path for LUN 0 will be:
/VenHw()/USB(0x0,0x0)/USB(0x1,0x0)/USB(0x4,0x0)/Ctrl(0x0)
Heinrich Schuchardt (2):
efi_loader: support for Ctrl() device path node
efi_loader: fix device-path for USB devices
include/efi_api.h | 6 ++++
lib/efi_loader/efi_device_path.c | 45 +++++++++++++++++-------
lib/efi_loader/efi_device_path_to_text.c | 7 ++++
3 files changed, 46 insertions(+), 12 deletions(-)
--
2.39.2
