Re: Warning! ehci_hcd should always be loaded before uhci_hcd and ohci_hcd

[Andrey Borzenkov <arvidjaar@mail.ru>]

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On Monday 22 of February 2010 10:00:53 Robby Workman wrote:
> On Mon, 22 Feb 2010 09:42:31 +0300
> 
> Andrey Borzenkov <arvidjaar@mail.ru> wrote:
> > ehci_hcd: USB 2.0 'Enhanced' Host Controller (EHCI) Driver
> > Warning! ehci_hcd should always be loaded before uhci_hcd and
> > ohci_hcd, not after
> > 
> > [snipped]
> > 
> > So my question is - is the warning still true? How serious problems
> > can result if uhci is loaded before ehci?
> > 
> > Does it make sense to workaround it in udev or may be trivial
> > 
> > install uhci_hcd mdprobe ehci_hcd; modprobe --ignore-install
> > uhci_hcd
> > 
> > would be enough?
> 
> That's basically what we did:
> 
> $ cat /etc/modprobe.d/usb-controller.conf
> # Make sure that ehci-hcd is always loaded before uhci-hci
> # # or ohci-hcd to prevent a kernel warning:
> install uhci-hcd /sbin/modprobe ehci-hcd ; /sbin/modprobe -i uhci-hcd
> install ohci-hcd /sbin/modprobe ehci-hcd ; /sbin/modprobe -i ohci-hcd
> 

The problem is this dependency strikes back in other places as well. 
E.g. I want to find out drivers for my USB keyboard to be loaded in 
initrd. Natural way is to walk up device tree collecting them - which 
leaves me with uhci (or ohci). Now I must manually do not forget to put 
in ehci, although strictly speaking I do not need it (in initrd) at all.

Kernel based solution would really be nice ...

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