libpayload: usb mass storage card hot plug

Mass storage devices such as card readers show up as
as USB devices. However the media not be inserted. In those
situations the previous code would just fake a disk and
call usbcreate_disk. This is inappropriate because it forms
a 1:1 mapping of USB device to disk leading to the inability
to remove the disk and/or handle "hot plug" card insertion
and removals.

To alleviate this issue introduce the notion of ready to the
usbmsc structure. It tracks detached, not ready, and ready
states. The polling routine is then used to track not ready
to ready transitions thereby creating and removing disks
appropriately. This handles the case of inserting and removing
a card that shows up as a new disk.

Booted recovery mode. Able to observe inerstion and removal
of sdcard. Also able to insert valid USB flash drive to boot
as well.

Change-Id: I3eefbe537ec1b9c975744b8984b06c17ae236f40
Signed-off-by: Aaron Durbin <>
Reviewed-by: Duncan Laurie <>
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <>
2 files changed