On Wed, 13 Feb 2019, Geert Uytterhoeven wrote: > On Wed, Feb 13, 2019 at 1:14 AM Finn Thain <fth...@telegraphics.com.au> wrote: > > On Tue, 12 Feb 2019, Geert Uytterhoeven wrote: > > > On Tue, Feb 12, 2019 at 6:31 AM Finn Thain <fth...@telegraphics.com.au> > > > wrote: > > > > There's an 'inverse' option in amifb, atafb, imstt, macfb, > > > > matroxfb, pvr2fb and vesafb. However, it's dead code in atafb, > > > > macfb, matroxfb and vesafb. The others use fb_invert_cmaps() but > > > > this has no effect on the framebuffer console. Does anyone know > > > > what this option is/was used for? > > > > > > To invert the console? ;-) > > > > > > Calling fb_invert_cmaps() inverts the default colormaps, and is thus > > > intended to have an effect on the frame buffer console. > > > > Calling fb_invert_cmaps() would affect all (new?) frame buffer > > consoles, right? If so, passing the same option to N drivers would > > defeat that setting, for even values of N. The effect of those > > settings would seem to depend on the driver probe order. > > True. This option dates back to the days only a single frame buffer > device could exist on the system. >
Makes sense. Many Linux systems still only support a single frame buffer. > > Anything we might do to fix this in matroxfb or vesafb has the potential > > to mess up someone's multi-driver setup. Is that why "inverse" is a no-op > > there? > > No idea. > > > > If this no longer works (due to some refactoring during the past +20 > > > years?), that's a bug. > > > > > > > Calling fb_invert_cmaps() doesn't seem to have any effect on aranym, qemu > > nor (I'm told) centris 650. Maybe the default cmap is never actually sent > > to the driver? > > Probably. Needs more investigation. I did some more investigation. When I tested macfb in qemu, I found that dafb_setpalette() is actually being called. And with this patch to add the missing call to fb_invert_cmaps(), the dafb_setpalette() parameters change accordingly. So I'll submit this patch again with signed-off-by. (The problem remains that dafb_setpalette() doesn't seem to have the desired effect on the hardware, but that's a separate issue.) > Or just remove the feature. Apparently no one used it during the last > +20 years, as no one complained. > On some powerbooks with greyscale LCD panels, the the black background is actually white, due to the backlight, and the white text is opaque black. This may or may not be optimal, depending on conditions etc. so I prefer not to remove macfb's 'inverse' option. -- > (Start of thread at https://www.spinics.net/lists/linux-m68k/msg13292.html) > > Gr{oetje,eeting}s, > > Geert > >
