[okl4-developer] serial driver l4_kdb

[Geoffrey Lee]

On Mon, May 26, 2008 at 01:09:43PM +1000, Josh Matthews wrote:

Hi Lukas,

> 
> 
> > Also, I am facing a problem with the kernel console. Iguana and the
> > Kernel use the same serial device, like in gumstix. When I send a char,
> > I get an interrupt delivered to my driver, but the data register of the
> > device is already empty. If, in the kernel's console.cc/get_c() function
> > I disable the reading of this register, it works. I programmed the
> > kernel timer for a 10ms tick.
> > Do you have an idea what I could do? E.g. is it possible to have kernel
> > and iguana use the same serial device?
> 
> 
> The problem you are seeing is a result of both the kernel and iguana using
> KDB for IO - I'd definitely recommend switching over to using a "real"
> serial device for applications.
> 

In addition to all of the points mentioned by Josh, I thought I would
just try to clear up this point.  We see similar problems on other 
boards as well.  This is mainly because there is a user level
driver for serial, but the kernel also has a driver for it, that is
independent of the one in user space.  Unfortunately at the moment
there is no way around this other than make the kernel and user space
serial driver use independent serial ports.

In practice the kernel driver gets removed in a production (no debug) 
build of OKL4, so this would not be an issue in a production environment.

	-gl



> Best regards,
> Josh Matthews

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