FB endianness

[Thomas Winischhofer]

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Keith Packard wrote:
| Around 2 o'clock on Jan 21, Thomas Winischhofer wrote:
|
|
|>Is there any way to "trick" the server into using a little-endian
|>(shadow) framebuffer on a big endian machine? Thinking of RGB ordering
|>and the like.
|
|
| You can make fb access the frame buffer 32 bits at a time, which should
| let you set whatever bit/byte order you want.


Can you kindly elaborate on this? How? Does this work for 16fbpp and
32fbpp? 8bpp clearly wouldn't be a problem.


| Note that fb doesn't handle
| mixed endian formats though.

No mixing required. Just little-endian.

|
| Are you sure it wouldn't be easier to just flip pixels on the way to the
| frame buffer?

Well, since the (changed) data in the shadow framebuffer is directly
handed over to the kernel and then transferred by DMA, flipping would be
a more or less severe performance brake on an already slow bus.

Thomas

- --
Thomas Winischhofer
Vienna/Austria
thomas AT winischhofer DOT net          http://www.winischhofer.net/
twini AT xfree86 DOT org
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