tree 73f2999a09067f70a74a52b073b78751af69d827
parent 954261595a1ca44378382408ca367dc70ca57d79
author Jack Pham <jackp@quicinc.com> 1621917170 -0700
committer Elliott Hughes <enh@google.com> 1624909555 -0700

adbd: Check USB disabled property after opening FFS

When a device with a DWC3 controller switches from host mode
back to peripheral mode, the USB HAL can set the sys.usb.adb.disabled
property to 0 to allow resumption of the usb_ffs_open_thread.

However when the kernel DWC3 driver switches modes it does the host
mode exit followed immediately by the gadget mode re-init in one fell
swoop. Furthermore, the re-adding of the gadget "UDC" device attempts
to immediately rebind the ConfigFS driver which is dependent on the
FunctionFS instance being ready to go, otherwise the operation fails.
Thus by the time USB HAL informs ADBD via the property change, there is
a race condition since the daemon must again open the FunctionFS
endpoints and reinitialize the descriptors before the kernel tries
to bind to the DWC3 gadget.

This can be avoided by moving the property check to after the
open_functionfs() call. This ensures ADBD will have prepared the
FFS descriptors and keeps the EP files open before pausing the thread
loop when in host mode. When leaving host mode the thread can pick
up from there and directly proceed to starting the monitor thread,
which satisfies the conditions needed for the gadget re-bind.

Bug: http://b/189256322
Change-Id: I57b0eede1ed14592d66065659d689285cae4102d