On Mon, Dec 31, 2018 at 12:34:31PM -0500, Alan Stern wrote:
> > Just a small addition, many Intel xHCI controllers now support 64 devices.
> >
> > It's possible to get the max device slots xHCI hardware supports from a xHC register.
> > (bits 7:0 of the HCSPARAMS1 capability register)
> >
> > This can be found from debugfs, but it's not very practical:
> >
> > mount -t debugfs none /sys/kernel/debug/
> > grep HCSPARAMS1 /sys/kernel/debug/usb/xhci/0000\:00\:14.0/reg-cap
> > HCSPARAMS1 = 0x1a000840
> >
> > We only care about bits 7:0, by ignoring the other bits we get 0x00000040,
> > which is 64 in decimal.
> >
> > So this xHCI supports 64 device slots.
>
> The limits that Marc encountered were on both the number of device
> slots and the number of endpoint slots. In his case, each device has 3
> endpoints.
For my own education, I was using USB/Serial converters and raw USB
(android fastboot).
Are there USB devices that only use 2 or 1 endpoint instead of 3 or
more?
Thanks,
Marc
--
"A mouse is a device used to point at the xterm you want to type in" - A.S.R.
Microsoft is to operating systems ....
.... what McDonalds is to gourmet cooking
Home page: http://marc.merlins.org/ | PGP 7F55D5F27AAF9D08
