mdev and post 3.6 kernels

Michael J. Hammel busybox at
Mon Feb 10 21:33:51 UTC 2014

On Mon, 2014-02-10 at 10:29 +0400, Michael Tokarev wrote:
> 09.02.2014 05:28, Michael J. Hammel wrote:
> > I've been using 3.2.27 from the RPi repos with mdev and usbfs.  This
> > worked fine to load drivers for wifi and webcams.  I'm trying to move to
> > RPi's "3.10.y" branch.  I've found that usbfs is deprecated and now I'm
> > not sure how to find the usb devices and load the drivers.  mdev doesn't
> > seem to report them.  I have it log every event at boot time and the usb
> > devices don't show up.  
> > 
> > Does anyone know if there are kernel config options that need to be
> > enabled in 3.6+ (when usbfs was deprecated) for mdev to be notified of
> > usb devices at boot time?  Or maybe suggestions on what mdev should be
> > looking at to find them?  I could dig into mdev but I'm not sure where
> > it should be looking for the devices.  lsusb shows them.  
> How about actually loading usb _controller_ drivers before trying to
> look up devices on usb bus?  Such as ehci_pci?
> (this has nothing to do with usbfs btw).

The RPi uses "Synopsis DWC host support" which is compiled into the
kernel for both 3.2.27 and 3.10.25 (aka RPis 3.10.y branch).
CONFIG_USB_ARCH_HAS_EHCI is not enabled in either kernel.  Other USB
options are also identical.  

I'm at work and can't get to my RPi to browse the USB device trees
under /sys/bus but I'm pretty sure the devices are there.  I believe
lsusb shows them.  I'll verify that tonight.  It appears, at least on
the surface, that its either some other kernel feature that needs to be
enabled in 3.10.x (that wasn't available or required in 3.2.27) or mdev
just isn't looking the right place for these devices.

I think these devices are there when mdev is run but the notification
mechanism between kernel and mdev is somehow changed in 3.10.x so mdev
isn't seeing them.

Michael J. Hammel <busybox at>

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