[linuxsh-dev] Re: [linux-sh:01337] Re: Debian GNU/Linux on Dreamcast

[M. R. B. <ma...@uw...>]

Hey guys,

On Wed, 25 Oct 2000, YAEGASHI Takeshi wrote:

> Hello Rene,
> 
> In the article <39F...@li...>,
> Rene Malmgren <re...@li...> wrote:
> 
> > Can someone please tell me what works and what doesn't yet, and how do
> > you get it to do? How far has the project come.
> 
> Linux is already ported to SEGA Dreamcast by me, privately.  It
> can boot from CD-R and have supports for serial port, frame
> buffer, and pad/keyboard.  Someone might see that Niibe gave a
> demonstration at Linux Kongress 2000.
> 
> Currently it can run only on the restricted environment with
> initrd.  It can handle none of GD-ROM, Audio or Ethernet yet
> from lack of sepcs...  Yes, all the information I could get was
> from Marcus Comstedt's DC site.
> 

Marcus Comstedt (http://mc.pp.se/dc/), Dan Potter (from this list) and
others on the dcdev list (at egroups) have exposed a lot of the
information necessary to write kernel drivers for various DC subsystems.
Info is available for:
  - Video modes: 320x240 565, 640x480 565, and 640x480 888.  That means a
    decent (albeit slow?) framebuffer can be constructed.
  - CD-ROM subsystem support.
  - Audio: I was thinking maybe a "generic" AICA firmware to emulate OSS
    or else a DC-specific audio spec.
  - Input: The DC's maple bus is spec'd, meaning keyboards, mice,
    controllers, VMUs are all avail.  The keyboard+fb is especially
    enticing.
  - Dan Potter has done some work regarding 2D-acceleration on the NEC
    PVR.  I haven't gotten a chance to really investigate this, but he
    suggested an accelerated framebuffer.

This is more than enough for us "hobbyists" to get started, other things
that could come later would be the expansion port (which gives us modem
and ethernet - eventually), better 3D support, etc.

> I'm sorry but I cannot release my port publicly, because I'm
> working for NAMCO, which has an NDA on Dreamcast with SEGA
> (actually I've not learned anything from SEGA under this NDA,
> but do they admit this fact?).  So I think I need SEGA's
> permission to release the port.

As far as kernel-specific (e.g. CONFIG_SH_DREAMCAST) stuff goes, do you
think you could release that?  I understand that you can't release
anything on the DC hardware, but could you give us some pointers on where
to get started on the actual port (e.g. how to structure devices, etc.).

> 
> 
> > First some DC / Linux questions:
> > 
> > Q1: Does someone have an ISO image to burn, or do you use the
> > serialslave to load the kernel from the DC?
> 
> I'm using GDB stub burned on CD-R to develop the kernel on
> Dremacast.
> 
>

Same here.  Still learning GDB though which is slowing me down a bit ;).
<leech> Do you have a .gdbinit you would recommend using? </leech>.
 
> > Q2: Is there an FB device that works with the PowerVR2 GFX. (As I
> > understand It the answer i NO)
> 
> Yes there is.  Framebuffer console is now working fine with
> SuperH Tux(many thanks to Greg:->).  We can login Dreamcast with
> keyboard or via serial port.
> 
>

I can't wait to get this working :)
 
> 
> Because Debian policy expects to be sh-linux-gcc(I heard gnu is
> reserved for Debian GNU/Hurd).  You can feel free to change the
> kernel's Makefile.
> 
> 
> > Q5: I have downloaded the kernel source from the CVS directory but fore
> > some reason it refuses to compile for GENERIC mode. Anyone who got a
> > clue why? Is it broken by default.
> 
> I cannot give any advice to you unless you tell me how it
> fails...
> 

It may be how the kernel include paths are setup, you have to make sure
that the kernel's includes are pointing to the sh-kernel directory and not
/usr/include or /usr/src/linux/include (if that's where your normal kernel
resides). 

> 
> > Q6: Are there any specific switches that should / shouldn't be used when
> > compiling the kernel to the DC. I thought of making a special "class"
> > fro the DC in the compiler script. Is this a good idea?
> 
> Agreed.  I've already added CONFIG_SH_DREAMCAST configuration to
> the kernel.
> 

Can you be more specific on this, without breaking NDA :)?

> 
> Any other comments, developers?
> 

It's cool that a licensed DC developer has ported Linux, but IMHO it would
benefit the community if hobbyists undertook this and got the kernel
stable on DC.  I'm very interested in pursuing this, anyone else up for
the challenge? :)

Those who are interested in Dreamcast programming at all should check out
the dcdev mailinglist at http://www.egroups.com.  Also good places to
start for info are Marcus's (not me) site: http://mc.pp.se/dc/, and Dan's
site: http://www.allusion.net/dcdev/.

> --
> YAEGASHI Takeshi <yae...@ma...>
> 
> 

M. R. Brown