[efi] Run at TPL_CALLBACK to protect against UEFI timers
As noted in the comments, UEFI manages to combines the all of the
worst aspects of both a polling design (inefficiency and inability to
sleep until something interesting happens) and of an interrupt-driven
design (the complexity of code that could be preempted at any time,
thanks to UEFI timers).
This causes problems in particular for UEFI USB keyboards: the
keyboard driver calls UsbAsyncInterruptTransfer() to set up a periodic
timer which is used to poll the USB bus. This poll may interrupt a
critical section within iPXE, typically resulting in list corruption
and either a hang or reboot.
Work around this problem by mirroring the BIOS design, in which we run
with interrupts disabled almost all of the time.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
[efi] Expose unused USB devices via EFI_USB_IO_PROTOCOL
Allow the UEFI platform firmware to provide drivers for unrecognised
devices, by exposing our own implementation of EFI_USB_IO_PROTOCOL.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Michael Brown