On 8/7/21 7:23 AM, Subhashini Rao Beerisetty wrote:

On Sat, Jul 31, 2021 at 11:12 AM Greg KH <gregkh@linuxfoundation.org> wrote:

...

On Fri, Jul 30, 2021 at 11:33:09PM +0530, Subhashini Rao Beerisetty wrote:

...

Hi All,

I'm currently looking for the Embedded USB Debug (EUD) interface driver.

For what specific hardware? Do you have the needed "special" cable? We have support in the kernel for some types of these cables, what kernel versions have you tried that did not work for this?

It's for MSM hardware and yes we have the "special" cable. I could not find the device driver for this in the mainline tree. It would be helpful if you could point me to the kernel tree which supports this feature. We will compile this suggested kernel and necessary drivers and then will give a try on our hardware

Hi, See USB_SERIAL_DEBUG in drivers/usb/serial/. That symbol builds usb_debug.c in that same directory. It may help to read Documentation/x86/earlyprintk.rst. My own cheat sheet (quick reference) says this: (it may or may not help you) (it might need some updating for XHCI): ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Using USB debug port (on a USB EHCI controller) On the system under test: CONFIG_USB_EHCI_HCD=y kernel command line: earlyprintk=dbgpN,keep With an XHCI controller, use: earlyprintk=xdbcN,keep Also add: console=tty0 or console=ttyUSB0 for console output to go to the serial port. Make sure that USB_SERIAL=y, USB_SERIAL_CONSOLE=y, and USB_SERIAL_DEBUG=y. ------ On the logging system: (requires CONFIG_USB_SERIAL_DEBUG=y) Run minicom and tell it to connect to /dev/ttyUSB#. Optionally have it log all messages to a file. ##### -- ~Randy