[BUG] efi_loader: incorrect creation of device paths

[Heinrich Schuchardt]

Hello Takahiro,

in a prior mail we have discussed the creation of device paths for USB
mass storage devices.

On the sand boxyou get the following devices after 'usb start':

  Class     Index  Probed  Driver                Name
-----------------------------------------------------------
  usb           0  [ + ]   usb_sandbox           |-- usb at 1
  usb_hub       0  [ + ]   usb_hub               |   `-- hub
  usb_mass_s    0  [ + ]   usb_mass_storage      |       |--
usb_mass_storage
  blk           3  [   ]   usb_storage_blk       |       |   `--
usb_mass_storage.lun0
  usb_mass_s    1  [ + ]   usb_mass_storage      |       |--
usb_mass_storage
  blk           4  [   ]   usb_storage_blk       |       |   `--
usb_mass_storage.lun0
  usb_mass_s    2  [ + ]   usb_mass_storage      |       `--
usb_mass_storage
  blk           5  [   ]   usb_storage_blk       |           `--
usb_mass_storage.lun0

For of these storage devices we try to create the same device path which
is not allowable:

=> usb start
starting USB...
Bus usb at 1: scanning bus usb at 1 for devices... 5 USB Device(s) found
        scanning usb for storage devices... 3 Storage Device(s) found
=>
=> efidebug dh
Scanning disk mmc2.blk...
handle 0000000015e34f00,
/VenHw(e61d73b9-a384-4acc-aeab-82e828f3628b)/SD(2)/SD(0)
Scanning disk mmc1.blk...
handle 0000000015e36b30,
/VenHw(e61d73b9-a384-4acc-aeab-82e828f3628b)/SD(1)/SD(1)
Scanning disk mmc0.blk...
handle 0000000015e35b00,
/VenHw(e61d73b9-a384-4acc-aeab-82e828f3628b)/SD(0)/SD(2)
Scanning disk usb_mass_storage.lun0...
handle 0000000015e35c10,
/VenHw(e61d73b9-a384-4acc-aeab-82e828f3628b)/UsbClass(0x1234,0x5678,0x9,0x0,0x0)/UsbClass(0x1234,0x5678,0x0,0x0,0x0)
fs_devread read outside partition 2
Failed to mount ext2 filesystem...
BTRFS: superblock end 69632 is larger than device size 512
Scanning disk usb_mass_storage.lun0...
handle 0000000015e361f0,
/VenHw(e61d73b9-a384-4acc-aeab-82e828f3628b)/UsbClass(0x1234,0x5678,0x9,0x0,0x0)/UsbClass(0x1234,0x5678,0x0,0x0,0x0)
ERROR: failure to add disk device usb_mass_storage.lun0, r = 20
Error: Cannot initialize UEFI sub-system, r = 20

I will provide a patch that will allow the first USB device to be used
and avoids stopping the boot process. But we really have to walk the dm
tree to create a device patch for USB devices based on port IDs.

We should add a new field to struct uclass_driver:

struct efi_device_path *get_node(udevice *dev);

This function shall return a pointer to an freshly allocated buffer with
the device node for the device. To build the devicepath we can then walk
the dm tree.

To make migration easier: If the function pointer or the return value is
NULL we can create a CTRL() node as dummy using the uclass_id and the
device number.

Best regards

Heinrich