Comment 2 for bug 1301161

StacktraceTop:
 gl646_setup_registers (depth=8, color=1, endx=10887, startx=15, linecnt=10, move=0, resolution=300, slope_table2=0x7fbabc149334, slope_table1=0x7fbabc149134, regs=0x7fbabc148be8, dev=0x7fbabc148bc0, scan_settings=...) at genesys_gl646.c:748
 setup_for_scan (dev=dev@entry=0x7fbabc148bc0, split=split@entry=1, xcorrection=xcorrection@entry=0, ycorrection=ycorrection@entry=0, settings=...) at genesys_gl646.c:3509
 simple_scan (dev=dev@entry=0x7fbabc148bc0, move=move@entry=0, forward=forward@entry=1, data=data@entry=0x7fbac382e9c0, shading=0, settings=...) at genesys_gl646.c:4994
 gl646_offset_calibration (dev=0x7fbabc148bc0) at genesys_gl646.c:4088
 genesys_flatbed_calibration (dev=0x7fbabc148bc0) at genesys.c:3339