On 7 July 2015 at 16:11, Sébastien Hinderer <Sebastien.Hinderer@ens-lyon.org> wrote:

Hi Luis,

Many thanks for your prompt and helpfulresponse!

> Do you have the relevant DEBUG macros activated in your kernel's
> configuration?

Perhaps not...

> https://www.kernel.org/doc/local/pr_debug.txt

Read this, thanks. But that has nothing to do with KConfigmacros, has
it?

> http://elinux.org/Debugging_by_printing
>
> If not, activate them. Or if in a pinch, switch to using pr_alert() for
> development.

What surprises me is that I made sue the message appears inthe .ko file
and it was there,whereas it seems pr_debug discards its argument at
compile time. Or is it at execution time?

Thanks!

Sébastien

Compile time. pr_debug() is meant only for development and discarded for "production" builds.

pr_debug(), which is ordinarily an empty macro that discards its arguments at compile time.
To enable debugging output, build the appropriate file with -DDEBUG by adding

CFLAGS_[filename].o := -DDEBUG

That is the key part there. But it is good to also check the options you have in:
make menuconfig-> Kernel Hacking

Enjoy,

Luis