drivers/char/hvc_* and /Documentation/powerpc/hvcs.txt

drivers/char/hvc_* and /Documentation/powerpc/hvcs.txt

[Timur Tabi]

Hi,

I'm working on a console driver for the Freescale hypervisor.  I notice a bunch 
of hvc_* files in the drivers/char directory.  I also noticed 
/Documentation/powerpc/hvcs.txt.

My guess is that hvcs.txt talks about drivers/char/hvcs.c, which is a console 
driver specific to some IBM hypervisor.  The hvc_*.c files are based on that 
code but they're more generic and allow people to write console drivers for 
other hypervisors easliy.  Am I right?

If so, does this mean that I can take hvc_beat.c, modify it to make Freescale 
hypervisor calls instead, and presto, I'm done?

-- 
Timur Tabi
Linux kernel developer at Freescale

Re: drivers/char/hvc_* and /Documentation/powerpc/hvcs.txt

[Olof Johansson]

On Fri, Jan 25, 2008 at 04:39:27PM -0600, Timur Tabi wrote:
> Hi,
> 
> I'm working on a console driver for the Freescale hypervisor.  I notice a bunch 
> of hvc_* files in the drivers/char directory.  I also noticed 
> /Documentation/powerpc/hvcs.txt.
> 
> My guess is that hvcs.txt talks about drivers/char/hvcs.c, which is a console 
> driver specific to some IBM hypervisor.  The hvc_*.c files are based on that 
> code but they're more generic and allow people to write console drivers for 
> other hypervisors easliy.  Am I right?

Hvcs is the server-side driver in some environments. I.e. a hvc console
connects through the hypervisor to a hvcs in another partition.

> If so, does this mean that I can take hvc_beat.c, modify it to make Freescale 
> hypervisor calls instead, and presto, I'm done?

Yep, pretty much. It's real easy to write a new backend to hvc, I've got
a couple for various bringup environments here as well.


-Olof

Re: drivers/char/hvc_* and /Documentation/powerpc/hvcs.txt

[Timur Tabi]

Olof Johansson wrote:

> Yep, pretty much. It's real easy to write a new backend to hvc, I've got
> a couple for various bringup environments here as well.

Could you tell me which kernel options I need to set/unset in order to get my 
driver to be called?  My driver loads and initializes, but its put_char function 
is never called.  Trying to debug to the console subsystem is making me dizzy.

-- 
Timur Tabi
Linux kernel developer at Freescale