On Wed, Nov 13, 2019 at 12:30:23PM -0700, Theo de Raadt wrote:
> These are usb devices.  There are multiple usb bus drivers, with
> usb2 and usb3 variations, and the usb subsystem itself.  The mailing
> lists are full of discussions of bugs in usb.
> But no, let's keep concluding these problems is narrowly restricted
> to a specific brand of device...

I have given up on trying to figure out non-obvious bugs in USB wifi
drivers for this reason. We need someone to look into USB issues in
order to make progress on the various hangs and power consumption
problems people have been reporting against drivers such as urtwn(4).

Granted, there could always be a bug in the wifi driver, but not having
reliable USB drivers beneath does not exactly help with debugging.

xhci(4) has problems on certain host controller models for instance.
We don't even have all the quirks and workarounds which other operating
systems apply to various host controller chipsets in our xhci(4) driver.
And then there are bugs specific to our implementation, such as this one
which was recently discovered by gerhard@:
We need more research into this area of bugs but we don't currently have
people who do it.

I also believe that bus power management in xhci(4) and ehci(4) is broken.
I cannot prove it, but it would be great if somebody looked into this to
find answers. athn(4) on USB seems to be suffering from something like this.

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