Bug 7691 - xf86-video-fbdev doesn't work with imacfb driver from linux-2.6.18-rcX
Summary: xf86-video-fbdev doesn't work with imacfb driver from linux-2.6.18-rcX
Alias: None
Product: xorg
Classification: Unclassified
Component: Driver/fbdev (show other bugs)
Version: 7.1 (2006.05)
Hardware: x86 (IA32) Linux (All)
: high normal
Assignee: Xorg Project Team
QA Contact:
Depends on:
Reported: 2006-07-30 04:46 UTC by Thomas Meyer
Modified: 2006-12-28 07:00 UTC (History)
1 user (show)

See Also:
i915 platform:
i915 features:


Description Thomas Meyer 2006-07-30 04:46:28 UTC
The imacfb driver from linux-2.6.16-rcX only works with the xf86-video-fbdev
driver with the option "ShadowFB "0". Without this option the display is kaputt.

See also http://bugs.gentoo.org/show_bug.cgi?id=140008.

This is maybe a problem in the imacfb driver, because it's to new?!
Comment 1 Thomas Meyer 2006-09-10 09:53:43 UTC
when i comment this in fbdev.c. the fbdev drvier is working with the shadow fb:
//      if (fPtr->shadowFB)
//              pScrn->displayWidth = pScrn->virtualX;  /* ShadowFB handles this
correctly */
//      else
                int fbbpp;
                /* FIXME: this doesn't work for all cases, e.g. when each scanline
                        has a padding which is independent from the depth
(controlfb) */
                pScrn->displayWidth = fbdevHWGetLineLength(pScrn)/(fbbpp >> 3);

So the value of pScrn->virtualX seems to be incorrect for a color depth of 24
bit and a bitsPerPixel = 32 bit.
and the comment "[..] handles this correclty" is obvious wrong.
Comment 2 Michel Dänzer 2006-09-10 14:20:07 UTC
The comment is correct. The fbdev driver can use whatever pitch it likes for the
shadow framebuffer. If ShadowFB doesn't work, that indicates a bug in either of

* the fbdev driver's use of the shadow module
* the shadow module
* the fbdevhw module
* imacfb

but not in this particular part of the fbdev driver code.
Comment 3 Vincent Rubiolo 2006-10-29 03:46:49 UTC

I can confirm I also have this bug on my Mactel 20' (I come from the
mactel-linux-devel ML). This is xorg 7.1.1 (Debian testing) w/ 2.6.18.

Is there anything we can do to help you diagnose the bug and find a fix?

Thanks for your guidance,

Comment 5 Thomas Meyer 2006-12-28 07:00:41 UTC
Excellent! Now the fbdev driver works correctly with the shadow framebuffer 
option. Many thanks for this fix.

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