Re: [PATCH v10 1/5] usb: xhci: Change the XHCI link order in the Makefile

[Andy Shevchenko]

On Wed, May 13, 2020 at 08:08:07AM -0700, Florian Fainelli wrote:
> On 5/13/2020 5:26 AM, Greg Kroah-Hartman wrote:
> > On Tue, May 12, 2020 at 11:00:15AM -0400, Al Cooper wrote:
> >> Some BRCMSTB USB chips have an XHCI, EHCI and OHCI controller
> >> on the same port where XHCI handles 3.0 devices, EHCI handles 2.0
> >> devices and OHCI handles <2.0 devices. Currently the Makefile
> >> has XHCI linking at the bottom which will result in the XHIC driver
> >> initalizing after the EHCI and OHCI drivers and any installed 3.0
> >> device will be seen as a 2.0 device. Moving the XHCI linking
> >> above the EHCI and OHCI linking fixes the issue.
> > 
> > What happens if all of these are modules and they are loaded in a
> > different order?  This makefile change will not help with that, you need
> > to have logic in the code in order to properly coordinate this type of
> > mess, sorry.
> 
> I believe we should be using module soft dependencies to instruct the
> module loaders to load the modules in the correct order, so something
> like this would do (not tested) for xhci-plat-hcd.c:
> 
> MODULE_SOFTDEP("post: ehci-hcd ohci-hcd");
> 
> and I am not sure whether we need to add the opposite for ehci-hcd and
> ohci-hcd:
> 
> MODULE_SOFTDEP("pre: xhci-plat-hcd");

JFYI: not all user space support this (alas, but that's current state of
affairs), OTOH I don't really care about those which do not support it
(Busybox).

-- 
With Best Regards,
Andy Shevchenko