libpayload: usb: Try to avoid reusing device addresses

Hardware / Coreboot - Julius Werner [chromium.org] - 22 December 2014 14:44 UTC

We recently changed the USB stack to detach devices aggressively that we don't intend to use. This alone is not really a problem, but it exarcerbates the fact that our device detachment itself is not very good. We destroy any local info about the device, but we don't properly disable the offending port. The device keeps thinking that it's active, and if we later try to reuse that device address for another device things become confused.

The real fix would be to properly disable all ports that we don't intend to use. Unfortunately, this isn't really possible in our current device/hub polymorphism structure, and I don't want to hack a new disable_port() callback into usbdev_t that really doesn't belong there. We will only be able to fix this cleanly after we ported all root hubs to the generic_hub interface.

Until then, an easy workaround is to just avoid reusing addresses as long as possible. This is firmware, so the chance that we'll ever run through 127 devices is really small in practice. Even if we ever fix the underlying issue, it's probably a smart precaution to keep.

BRANCH=nyan,rambi BUG=chrome-os-partner:28328 TEST=Boot from a hub that has an "unknown" device in an earlier port than the stick you want to boot from, make sure you can still boot.

Original-Change-Id: I9b522dd8cbcd441e8c3b8781fcecd2effa0f23ee

6af4380 libpayload: usb: Try to avoid reusing device addresses
payloads/libpayload/drivers/usb/usb.c | 14 +++++++++++---
payloads/libpayload/include/usb/usb.h | 1 +
2 files changed, 12 insertions(+), 3 deletions(-)

Upstream: review.coreboot.org

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