tangobravo
Posts: 9
Joined: Sun Sep 04, 2011 7:27 pm

Re: Framebuffer for other OSes?

Sun Sep 04, 2011 9:14 pm

Hi all,

First off I think this is a great project. I'll definitely be buying a board.

I've read around and I realise that R-Pi isn't really aimed at people wanting a hardware platform to hack about on, but I'd be interested in looking at getting something non-linux running (specifically Haiku, but their ARM port isn't particularly advanced). I know the Videocore "firmware" will stay a binary blob, which is fine (as it sounds like that's loaded by the GPU itself before the ARM core is even booted), and that the advanced accelerated multimedia stuff is unlikely to be exposed, but is it plausible I'll be able to set up a 2D framebuffer and write into it without needing any Broadcom binary blobs?

I did Engineering at Cambridge and have a bit of ARM experience, but I'd be mostly poking around in the dark on this one!

Simon

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liz
Raspberry Pi Foundation Employee & Forum Moderator
Raspberry Pi Foundation Employee & Forum Moderator
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Joined: Thu Jul 28, 2011 7:22 pm
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Re: Framebuffer for other OSes?

Sun Sep 04, 2011 9:16 pm

Effectively, you'll just need to write a width, height and base pointer into a magic location in memory, and the blob grabs it and sticks it on the screen. Houpla!
Director of Communications, Raspberry Pi

tangobravo
Posts: 9
Joined: Sun Sep 04, 2011 7:27 pm

Re: Framebuffer for other OSes?

Mon Sep 05, 2011 7:07 am

Awesome, thanks for the reply.

There's a thread on the Haiku mailing list about R-pi currently (how I discovered you yesterday), and it sounds like there is plenty of work other than graphics that would be needed - timers, interrupt controllers, etc, but I assume all of the source for those bits would be open in the linux kernel, or with documentation available from Broadcom?

I've never really dabbled in anything kernel-level, but always been interested to have a go.

DOSGuy
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Joined: Tue Sep 06, 2011 1:33 pm
Contact: Website

Re: Framebuffer for other OSes?

Tue Sep 06, 2011 2:40 pm

There's also an ARM port of ReactOS, so there's at least a possibility of running a Windows-like OS on the R-Pi before Windows 8 arrives.

tangobravo
Posts: 9
Joined: Sun Sep 04, 2011 7:27 pm

Re: Framebuffer for other OSes?

Tue Sep 06, 2011 5:26 pm

I've read the long SoC thread, but I think that got a bit derailed, so I'm going to ask in this one instead.

I believe the Videocore architecture is a bit different in that the Videocore does all the GL state tracking and stuff that would usually be done in the host OS driver (or by Gallium3D). I believe the host OS just passes some messages to the GPU. Is that message-passing bit going to be covered in whatever datasheets get released publicly? The other avenue is to see the source for the linux host driver but I understand the decision on whether to open-source those bits or not hasn't been made yet.

rwaltman
Posts: 31
Joined: Mon Sep 05, 2011 3:16 pm

Re: Framebuffer for other OSes?

Tue Sep 06, 2011 10:06 pm

... need to write a width, height and base pointer into a ... location in memory, and the blob grabs it and sticks it on the screen.

Good to know. I can make the same memory area available via Ethernet to a VNC like interface, and have local and/or remote displays with little effort.
--
Roberto Waltman

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