framebuffer swap endianess

4 messages, 4 authors, 2008-01-23 · open the first message on its own page

framebuffer swap endianess

From: Angelo <hidden>
Date: 2008-01-22 15:53:29

Hi, i'm angelo.

I have just create a framebuffer for an embedded system:
- powerpc (little endian)  with  a GPU (big endian).

I'm working on linux 2.6.22

When i try to execute Xfbdev, it starts but with wrong colors.
I need to swap the RGB format (RRRRRGGGGGGBBBBB) to BGR, respecting the endianess (GGGRRRRRBBBBBGGG).

I know that X loads with some ioctl, the principal settings through framebuffer.
But i'm not sure if framebuffer can inform it on the RGB format.

I also tried to change something on cmap, but nothing changes on display;

So, i hope you can help me. 

Many thanks.


       
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Re: framebuffer swap endianess

From: Josh Boyer <hidden>
Date: 2008-01-22 16:45:52

On Tue, 22 Jan 2008 16:46:47 +0100 (CET)
Angelo [off-list ref] wrote:
Hi, i'm angelo.

I have just create a framebuffer for an embedded system:
- powerpc (little endian)  with  a GPU (big endian).
I think you have those backwards?  PowerPC is big-endian...

josh

Re: framebuffer swap endianess

From: Roman Fietze <hidden>
Date: 2008-01-23 07:46:10

Hello ANgelo,

On Tuesday 22 January 2008 16:46:47 Angelo wrote:
I have just create a framebuffer for an embedded system:
- powerpc (little endian)  with  a GPU (big endian).
Are you sure? Isn't it the other way around?
When i try to execute Xfbdev, it starts but with wrong colors.  I
need to swap the RGB format (RRRRRGGGGGGBBBBB) to BGR, respecting
the endianess (GGGRRRRRBBBBBGGG).
We modified the X Server and swapped when transferring from the shadow
buffer to the video buffer. That cured all our problems. This was on
the 2.4.25 from DENX and with Xfree86.

Other modifications like changing the RGB masks for the display/screen
only helped partwise, because some applications just ignored that when
using some image formats.


Roman

=2D-=20
Roman Fietze Telemotive AG B=FCro M=FChlhausen

Re: framebuffer swap endianess

From: Kumar Gala <hidden>
Date: 2008-01-23 16:39:18

On Jan 23, 2008, at 1:39 AM, Roman Fietze wrote:
Hello ANgelo,

On Tuesday 22 January 2008 16:46:47 Angelo wrote:
quoted
I have just create a framebuffer for an embedded system:
- powerpc (little endian)  with  a GPU (big endian).
Are you sure? Isn't it the other way around?
we are sure.  Linux only supports PPC in big endian mode.

  - k
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