[okl4-developer] serial driver l4_kdb

[Geoffrey Lee]

On Fri, May 16, 2008 at 05:34:29PM +0200, Lukas HANEL wrote:
> Hello
> 
> I am currently trying to get the iguana drivers example to work on my
> machine. Therefore
> I currently want to use the l4_kdb driver in v2 framework.
> 
> When testing the examples that do not need drivers, I was already seeing
> output. How does this go in line with the possibility to explicitly set
> the kernel debugger as serial console?

Your printf() gets routed to libs/c/sys-*/ 's appropriate write
functions.  For Iguana applications, this means going out via
kdb's character print functions.

> 
> If iguana is already using kdb, is it possible to also provide a virtual
> serial server using kdb, such that Linux can use it?
> 


Output via kdb can go out in one of the following two ways:

(1) your printf() or whatever libc print function gets routed to
libs/c/sys-*/ which ends up calling the kdb character print
functions, or you implement your own such as print function
and end up calling the kdb character print functions directly

(2) you use vserial for your i/o.  In this instance you don't
really care what the backend is.  If you choose to use l4kdb_uart,
it will do a cheesy emulation of a serial device, enough to
read and write, anyway.

OK Linux uses both methods, (1) for kernel message output and (2)
to implement consoles for, say, interactive shells.


> Problems:
> But there are two packages,
>   drv_l4_kdb,
>   l4kdb_uart.
> Which one do I want to use?

l4kdb_uart.  We deprecated the l4kdb_uart driver a while ago and
is no longer used in any supported configuration.  Having
said this this wasn't too long ago, the errors you see are probably
a result of bit-rot and it should not be too difficult to fix it
so it is up to date.  In any case I recommend implementing
a proper serial driver.

	-gl