<div dir="ltr"><div>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.<br><br></div>Thanks.<br></div><div class="gmail_extra"><br><div class="gmail_quote">On Wed, Apr 26, 2017 at 5:49 AM, Greg KH <span dir="ltr"><<a href="mailto:greg@kroah.com" target="_blank">greg@kroah.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><span class="">On Wed, Apr 26, 2017 at 01:23:55PM +0200, Oliver Graute wrote:<br>
> On 26/04/17, Greg KH wrote:<br>
> > On Tue, Apr 25, 2017 at 11:11:38PM +0200, Oliver Graute wrote:<br>
> > > Hello list,<br>
> > ><br>
> > > i'am using a null modem cable with two usb to serial converts on both<br>
> > > ends between my develop and my target machine. The connection is fine.<br>
> > > On both machines the serial interface is /dev/ttyUSB0 for this connection.<br>
> > ><br>
> > > On the target machine I try to enable kgdboc<br>
> > ><br>
> > > echo ttyUSB0 > /sys/module/kgdboc/parameters/<wbr>kgdboc<br>
> > ><br>
> > > but only got:<br>
> > ><br>
> > > echo write error: No such device<br>
> > ><br>
> > > if I try:<br>
> > ><br>
> > > echo ttyS0 > /sys/module/kgdboc/parameters/<wbr>kgdboc<br>
> > ><br>
> > > is not complaining. Some ideas why ttyUSB0 can't be used with kgdb?<br>
> ><br>
> > USB needs interrupts in order to run properly, which kgdb doesn't enable<br>
> > when you stop the target, for obvious reasons :)<br>
><br>
> ok that make sense<br>
><br>
> > Stick to a "real" serial connection and you should be fine.<br>
><br>
> thats not so easy. Even the old notebooks today lacks a "real" serial<br>
> connection. Perhaps I should use a raspberry as target. There I can get<br>
> a serial over the gpios.<br>
<br>
</span>Why do you need to use a notebook where Linux works already for kgdb?<br>
That's traditionally only used to bring up new hardware platforms.<br>
<br>
Also, there is USB serial debugging cables as there is a special mode in<br>
the USB 2 and 3 controllers that can be enabled to handle serial<br>
messages without interrupts for console/printk early messages that<br>
people use. The cables are not cheap to enable this, but worth it if<br>
you have to debug this type of target system.<br>
<br>
Good luck!<br>
<br>
greg k-h<br>
<div class="HOEnZb"><div class="h5"><br>
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</div></div></blockquote></div><br><br clear="all"><br>-- <br><div class="gmail_signature" data-smartmail="gmail_signature">JS</div>
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