[plug] Kernel hacking advice needed

[Owain]

On 19 Apr 2013 01:39, "Andrew Cooks" <acooks at gmail.com> wrote:
>
> Hi Owain
>
> How's the kernel hacking going?

Not bad thanks! I felt a bit lost for a while, but once I started to get
actual debug information from the kernel things started to gel.

The chip I was planning on adding was an io expander which added to my
confusion as it was using spi and gpios to provide more gpios. With
hindsight I should have gone for an easier chip.

> >> Firstly I'm in embedded land and don't really have the full set of
> >> tools that I'm used to. When I modprobe the module I don't get any
> >> errors on my serial console, but I don't have access to dmesg - so I'm
> >> not too sure where any kernel messages are being put - I know that
> >> printk messages are sent to the serial console I'm monitoring.
>
> Do you mean that 'dmesg' is not included in your userland tools, or is
> it not available for a different reason?

Sorry, I forgot to mention I recompiled the busybox binary i was using to
include dmesg. It was a bit of a squeeze, but I got there.

> > That should be sufficient then. Might be good to put 'debug' on the
> > kernel command line so that you get all levels of printk messages.
>
> There's a slight gotcha with the 'debug' kernel parameter : you still
> won't see debug level messages during boot (but will see them using
> 'dmesg' iirc). To really see everything, you can use the
> 'ignore_loglevel' parameter, but I've found selective printing with
> 'dyndbg' much more useful.

Would that be available for the 2.6 kernel I'm stuck on?

> Cheers,
>
> a.

Thanks for the support. Getting the debug messages were the key :). Find a
book - Kernel device drivers, third edition, published by o'reilly helped
massively also.

Thanks,

Owain
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