kernel debugging

Richard A. Smith richard at
Tue Aug 4 11:47:05 EDT 2009

NoiseEHC wrote:

> Somehow every time I asked about debugging in these forums I have got no 
> answer at all. Now I have a weak feeling that Linux developers are "real 
> programmers" who do not use debuggers. I hope it is not the case...  :) 
>> > 2.

Or they are just busy...

>> Another issue is that this serial stuff will be loaded much later than 
>> kernel start so if I define "console=/dev/ttyUSB0" in the kernel 
>> parameters and the device will be created later then will Linux pick 
>> up the device at that time?

If you want a USB serial console early then you have to compile the USB 
serial drivers statically into the kernel and verify that your initrd 
will have a /dev/ttyUSB0 ready for use.

> plug into the serial cable, the serial cable's plug into the FTDI bridge 
> and the bridge into the XO-1. Then I started getty ttyS0 or something 
> similar and nothing happened. Exactly how could I test the setup?

You should spend some time with google learning about how rs232/serial 
connections work both hardware and software.  Otherwise there is a large 
amount of terminology that you won't understand in any help you receive.

Step one in debugging serial connections is a loopback device which 
shorts TX and RX so you can test each part of the chain.

Richard Smith  <richard at>
One Laptop Per Child

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