Re: [PATCH v3] fbcon: add fbcon=margin:<color> command line option

[David Lechner]

On 08/18/2017 01:21 PM, Geert Uytterhoeven wrote:
> Hi David,
>
> On Tue, Aug 1, 2017 at 6:35 PM, David Lechner <david@xxxxxxxxxxxxxx> wrote:
> > This adds a new command line option to select the fbcon margin color.
> >
> > The motivation for this is screens where black does not blend into the
> > physical surroundings of the screen. For example, using an LCD (not the
> > backlit kind), white text on a black background is hard to read, so
> > inverting the colors is preferred. However, when you do this, most of the
> > screen is filled with white but the margins are still filled with black.
> > This makes a big, black, backwards 'L' on the screen. By setting
> > fbcon=margin:7, the margins will be filled with white and the LCD looks as
> > expected.
> >
> > Signed-off-by: David Lechner <david@xxxxxxxxxxxxxx>
>
> > --- a/Documentation/fb/fbcon.txt
> > +++ b/Documentation/fb/fbcon.txt
> > @@ -148,6 +148,13 @@ C. Boot options
> >          Actually, the underlying fb driver is totally ignorant of console
> >          rotation.
> >
> > +5. fbcon=margin:<color>
> > +
> > +       This option specifies the color of the margins. The margins are the
> > +       leftover area at the right and the bottom of the screen that are not
> > +       used by text. By default, this area will be black. The 'color' value
> > +       is 0 to 7 where 0 is black and 7 is white.
> > +
>
> Given the standard console palette contains 16 colors, why limit this to
> the first 8 colors, and not 0 to 15?

Good question. I think in some of my previous attempts there was a 0x7 
mask involved somewhere and this is a carryover from that. But, after 
having looked at this again, I don't see a reason for limiting to 7.