Rotating the display via xrandr causes the X server to segfualt. This has
happened to me on both x86 ( Xvesa ) and ARM ( XFbdev ). 

Here is a backtrace caused by 'xrandr -o left'

--

Starting program: /usr/local/kx/bin/Xvesa -ac

Program received signal SIGSEGV, Segmentation fault.
0x0809489f in fbBlt (srcLine=0x824b410, srcStride=4, srcX=0, 
    dstLine=0x401d1b20, dstStride=80, dstX=4, width=128, height=31, 
    alu=136623108, pm=1075648992, bpp=4, reverse=0, upsidedown=458759)
    at fbblt.c:298
298                             dst++;
(gdb) bt
#0  0x0809489f in fbBlt (srcLine=0x824b410, srcStride=4, srcX=0, 
    dstLine=0x401d1b20, dstStride=80, dstX=4, width=128, height=31, 
    alu=136623108, pm=1075648992, bpp=4, reverse=0, upsidedown=458759)
    at fbblt.c:298
#1  0x0809c244 in fbCopyNtoN (pSrcDrawable=0x824b400, pDstDrawable=0x81204c0, 
    pGC=0x700070, pbox=0xbffff4d8, nbox=-1, dx=-305, dy=-225, reverse=0, 
    upsidedown=0, bitplane=0, closure=0x0) at fbcopy.c:71
#2  0x0809c9ad in fbCopyRegion (pSrcDrawable=0x824b3c8, 
    pDstDrawable=0x81204c0, pGC=0xf, pDstRegion=0xf, dx=-305, dy=-225, 
    copyProc=0x809c040 <fbCopyNtoN>, bitPlane=15, closure=0xf) at fbcopy.c:377
#3  0x0809ce38 in fbDoCopy (pSrcDrawable=0x824b3c8, pDstDrawable=0x81204c0, 
    pGC=0x8113f68, xIn=0, yIn=0, widthSrc=32, heightSrc=32, xOut=305, 
    yOut=225, copyProc=0xf, bitPlane=0, closure=0xf) at fbcopy.c:568
#4  0x0809d01e in fbCopyArea (pSrcDrawable=0xf, pDstDrawable=0xf, pGC=0xf, 
    xIn=15, yIn=15, widthSrc=15, heightSrc=15, xOut=15, yOut=15)
    at fbcopy.c:598
#5  0x080e8481 in damageCopyArea (pSrc=0xf, pDst=0x81204c0, pGC=0x8113f68, 
    srcx=15, srcy=15, width=32, height=32, dstx=305, dsty=225) at damage.c:673
#6  0x080b3d4a in miDCRestoreUnderCursor (pScreen=0x700070, x=15, y=15, w=15, 
    h=15) at midispcur.c:564
#7  0x080beed1 in miSpriteRemoveCursor (pScreen=0x8115260) at misprite.c:755
#8  0x080e74df in damageDamageRegion (pDrawable=0x81204c0, pRegion=0x8113f48, 
    clip=0) at damage.c:182
---Type <return> to continue, or q <return> to quit---
#9  0x080ea5cb in damagePaintWindow (pWindow=0x81204c0, prgn=0x8113f48, what=0)
    at damage.c:1450
#10 0x080e5a3f in compPaintWindowBackground (pWin=0x80e59e0, pRegion=0xf, 
    what=15) at compwindow.c:186
#11 0x080b5138 in miWindowExposures (pWin=0x81204c0, prgn=0x8113f48, 
    other_exposed=0x0) at miexpose.c:539
#12 0x080c56ce in miHandleValidateExposures (pWin=0x81204c0) at miwindow.c:471
#13 0x08085539 in KdSetRootClip (pScreen=0x8115260, enable=1 '\001')
    at kdrive.c:193
#14 0x080858f9 in KdEnableScreen (pScreen=0x8115260) at kdrive.c:296
#15 0x0804cc68 in vesaRandRSetConfig (pScreen=0x8115260, randr=2, rate=0, 
    pSize=0x700070) at vesa.c:1250
#16 0x080dfe23 in ProcRRSetScreenConfig (client=0x824bab8) at randr.c:827
#17 0x0805f52f in Dispatch () at dispatch.c:454
#18 0x08050215 in main (argc=2, argv=0xbffffe04, envp=0xf) at main.c:438

--

This is a real blocker for running the composite stuff on handhelds.