[Letux-kernel] [Staff] USB udc problem with 4.5-rc

H. Nikolaus Schaller hns at goldelico.com
Thu Mar 10 17:53:48 CET 2016

Hi Lukas,

> Am 10.03.2016 um 17:08 schrieb Lukas Maerdian <lukas at goldelico.com>:
> Hi,
> I did rebase my android kernel tree to letux-base (4.5-rc7) today.
> Unfortunately quite some stuff seems to be broken, so I only get access
> via the serial console.


> Most importantly the FunctionFS (used to access the device via USB/ADB)
> is not working. Whenever I try to restart the adb daemon on the GTA04 I
> can see the following error:
> root at android:/ # restart adbd
> root at android:/ # [  665.916717] read descriptors
> [  665.920257] read strings
> [  665.923217] udc-core: couldn't find an available UDC - added [g_ffs]
> to list of pending drivers


> This message comes from a change, which was introduced into the USB
> gadget subsystem during the 4.5 merge window and changes the UDC and
> Gadget registration process:
> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/drivers/usb/gadget/udc/udc-core.c?id=855ed04a3758b205e84b269f92d26ab36ed8e2f7
> It does not find any USB Device Controller (UDC), when loading the
> FunctionFS. What is the UDC used on our OMAP3?

I don't know... Even I don't know what UDC is...

> And is there a driver for
> it? I found an "omap_udc" driver in drivers/usb/gadget/udc, but this
> seems to be for OMAP1 only.

How did that work on the 4.4 kernel?

> Other than that the backlight driver is not working, too, even though
> the pwm_bl and pwm_omap_dmtimer modules are loaded. Are you aware of any
> relevant changes in the PWM subsystem?

No, it should work out of the box. It may be necessary to load some more
kernel modules.

I will boot my GTA04 and send the lsmod asap.


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