kgdb debug with ttyUSB0 instead of ttyS0
Hello list, i'am using a null modem cable with two usb to serial converts on both ends between my develop and my target machine. The connection is fine. On both machines the serial interface is /dev/ttyUSB0 for this connection. On the target machine I try to enable kgdboc echo ttyUSB0 > /sys/module/kgdboc/parameters/kgdboc but only got: echo write error: No such device if I try: echo ttyS0 > /sys/module/kgdboc/parameters/kgdboc is not complaining. Some ideas why ttyUSB0 can't be used with kgdb? Best regards, Oliver
echo ttyUSB0 > /sys/module/kgdboc/parameters/kgdboc
but only got:
echo write error: No such device
Is the USB-to-serial device detected on your target? Do you see a ttyUSB0 device node on your target? You can look at the kernel logs on your target when you insert the device. If the kernel has the drivers for it, you should see a device node being created. -mandeep
if I try:
echo ttyS0 > /sys/module/kgdboc/parameters/kgdboc
is not complaining. Some ideas why ttyUSB0 can't be used with kgdb?
Best regards,
Oliver
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On Tue, Apr 25, 2017 at 11:11:38PM +0200, Oliver Graute wrote:
Hello list,
i'am using a null modem cable with two usb to serial converts on both ends between my develop and my target machine. The connection is fine. On both machines the serial interface is /dev/ttyUSB0 for this connection.
On the target machine I try to enable kgdboc
echo ttyUSB0 > /sys/module/kgdboc/parameters/kgdboc
but only got:
echo write error: No such device
if I try:
echo ttyS0 > /sys/module/kgdboc/parameters/kgdboc
is not complaining. Some ideas why ttyUSB0 can't be used with kgdb?
USB needs interrupts in order to run properly, which kgdb doesn't enable when you stop the target, for obvious reasons :) Stick to a "real" serial connection and you should be fine. good luck! greg k-h
On 26/04/17, Greg KH wrote:
On Tue, Apr 25, 2017 at 11:11:38PM +0200, Oliver Graute wrote:
Hello list,
i'am using a null modem cable with two usb to serial converts on both ends between my develop and my target machine. The connection is fine. On both machines the serial interface is /dev/ttyUSB0 for this connection.
On the target machine I try to enable kgdboc
echo ttyUSB0 > /sys/module/kgdboc/parameters/kgdboc
but only got:
echo write error: No such device
if I try:
echo ttyS0 > /sys/module/kgdboc/parameters/kgdboc
is not complaining. Some ideas why ttyUSB0 can't be used with kgdb?
USB needs interrupts in order to run properly, which kgdb doesn't enable when you stop the target, for obvious reasons :)
ok that make sense
Stick to a "real" serial connection and you should be fine.
thats not so easy. Even the old notebooks today lacks a "real" serial connection. Perhaps I should use a raspberry as target. There I can get a serial over the gpios. Best Regards, Oliver
On Wed, Apr 26, 2017 at 01:23:55PM +0200, Oliver Graute wrote:
On 26/04/17, Greg KH wrote:
On Tue, Apr 25, 2017 at 11:11:38PM +0200, Oliver Graute wrote:
Hello list,
i'am using a null modem cable with two usb to serial converts on both ends between my develop and my target machine. The connection is fine. On both machines the serial interface is /dev/ttyUSB0 for this connection.
On the target machine I try to enable kgdboc
echo ttyUSB0 > /sys/module/kgdboc/parameters/kgdboc
but only got:
echo write error: No such device
if I try:
echo ttyS0 > /sys/module/kgdboc/parameters/kgdboc
is not complaining. Some ideas why ttyUSB0 can't be used with kgdb?
USB needs interrupts in order to run properly, which kgdb doesn't enable when you stop the target, for obvious reasons :)
ok that make sense
Stick to a "real" serial connection and you should be fine.
thats not so easy. Even the old notebooks today lacks a "real" serial connection. Perhaps I should use a raspberry as target. There I can get a serial over the gpios.
Why do you need to use a notebook where Linux works already for kgdb? That's traditionally only used to bring up new hardware platforms. Also, there is USB serial debugging cables as there is a special mode in the USB 2 and 3 controllers that can be enabled to handle serial messages without interrupts for console/printk early messages that people use. The cables are not cheap to enable this, but worth it if you have to debug this type of target system. Good luck! greg k-h
The options you suggested are not clear to me. Can you elaborate how I would debug live kernel when all I have on the two systems is usb. Can you list the cable that I can use/order. Thanks. On Wed, Apr 26, 2017 at 5:49 AM, Greg KH <greg@kroah.com> wrote:
On Wed, Apr 26, 2017 at 01:23:55PM +0200, Oliver Graute wrote:
On 26/04/17, Greg KH wrote:
On Tue, Apr 25, 2017 at 11:11:38PM +0200, Oliver Graute wrote:
Hello list,
i'am using a null modem cable with two usb to serial converts on both ends between my develop and my target machine. The connection is fine. On both machines the serial interface is /dev/ttyUSB0 for this connection.
On the target machine I try to enable kgdboc
echo ttyUSB0 > /sys/module/kgdboc/parameters/kgdboc
but only got:
echo write error: No such device
if I try:
echo ttyS0 > /sys/module/kgdboc/parameters/kgdboc
is not complaining. Some ideas why ttyUSB0 can't be used with kgdb?
USB needs interrupts in order to run properly, which kgdb doesn't enable when you stop the target, for obvious reasons :)
ok that make sense
Stick to a "real" serial connection and you should be fine.
thats not so easy. Even the old notebooks today lacks a "real" serial connection. Perhaps I should use a raspberry as target. There I can get a serial over the gpios.
Why do you need to use a notebook where Linux works already for kgdb? That's traditionally only used to bring up new hardware platforms.
Also, there is USB serial debugging cables as there is a special mode in the USB 2 and 3 controllers that can be enabled to handle serial messages without interrupts for console/printk early messages that people use. The cables are not cheap to enable this, but worth it if you have to debug this type of target system.
Good luck!
greg k-h
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-- JS
On 26/04/17, Greg KH wrote:
Why do you need to use a notebook where Linux works already for kgdb? That's traditionally only used to bring up new hardware platforms.
I just used a old notebook as target to learn how-to debug with kgdb. inspired by the debugging Chapter 4 in the LDD3 Book.
Also, there is USB serial debugging cables as there is a special mode in the USB 2 and 3 controllers that can be enabled to handle serial messages without interrupts for console/printk early messages that people use. The cables are not cheap to enable this, but worth it if you have to debug this type of target system.
can you point us to such a cable? Best Regards, Oliver
participants (4)
-
Greg KH -
Joe Smith -
Mandeep Sandhu -
Oliver Graute