On 02/11/16 12:30, Dee Zay wrote:
Hello,
I am a bit confused about the resume problem and its procedures.
Could you explain briefly about the difference between resuming from
standby(powered) and completely off HC?
Thank you,
Julian
Hi,
Only the XHCI can resume completely off HC. It knows about which devices
are enumerated and so on. The other HC's don't.
You need to ensure that filesystem reloads everything when you resume.
No assumptions can be made about which disk is connected. A USB keyboard
is simpler, of course.
There is also something called a BIOS, which sometimes enable and
enumerate the USB devices before the OS is resuming. I think there is a
standard somewhere how the BIOS can handover enumerated devices to the
USB stack, but I'm not sure if it is public. In any case FreeBSD will
reset the HC and start from scratch when resuming. That always works.
--HPS
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