Endianess problem in fbcon and cfbimgblt when using monochrome fb

Endianess problem in fbcon and cfbimgblt when using monochrome fb

[Mike Wolfram]

Hi,

I have written a framebuffer driver for an Epson SED1335 based LCD for the ARM 
platform. The LCD is monochrome, so the driver currently only supports 1 bpp. 
The ARM is little-endian.

Everything works fine except when using the fbcon. All text printed to that 
console appears with having each character mirrored on the y axis. So it 
looks like an endian problem.

I found a message from April ("[patch 19/26] fbcon: Fix big-endian bogosity in 
slow_imageblit()") which fixes a problem for big-endian machines. After 
reverting that patch and changing

#define FB_BIT_NR(b)              (b)

to

#define FB_BIT_NR(b)              (7 - (b))

the text appears as expected. So my question is if the patch might be wrong 
and should only change the defines for FB_BIT_NR? Or could the problem be 
somewhere else?

Regards,
Mike Wolfram
-- 
MicroDatec GmbH
Zeulenrodaer Str. 17, 99091 Erfurt, Germany
fon +49-361-77821-0, fax +49-361-77821-30
mobile +49-179-4902190

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Re: Endianess problem in fbcon and cfbimgblt when using monochrome fb

[Michel Dänzer]

On Mon, 2006-10-02 at 14:03 +0200, Mike Wolfram wrote:
> 
> I have written a framebuffer driver for an Epson SED1335 based LCD for the ARM 
> platform. The LCD is monochrome, so the driver currently only supports 1 bpp. 
> The ARM is little-endian.
> 
> Everything works fine except when using the fbcon. All text printed to that 
> console appears with having each character mirrored on the y axis. So it 
> looks like an endian problem.

No, endianness is only about byte order, not bit order.


-- 
Earthling Michel Dänzer           |          http://tungstengraphics.com
Libre software enthusiast         |          Debian, X and DRI developer


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