Re: [Linux-fbdev-devel] Supporting various depth

[Geert U. <ge...@li...>]

On Wed, 13 Jun 2001, Sven LUTHER wrote:
> On Wed, Jun 13, 2001 at 03:49:41PM +0200, Geert Uytterhoeven wrote:
> > On Wed, 13 Jun 2001, Romain Dolbeau wrote:
> > > Is there a way to distinguish 15 and 16 bpp in 16bits pixels in
> > > the fbdev/fbcon layer ?
> > 
> > Yes, by looking at the fb_var_screeninfo.{red,green,blue}.length fields.
> > 
> > > pm3fb support RGB565 in 16bpp, and I was just asked for 15bpp
> > > (RGB555 + 1 bit Alpha or whatever). Do I simply reuse CFB16
> > > and support both internally, is there a requirement that
> > > CFB16 is one or the other, ... ?
> > 
> > Cfb16 is the memory organization: packed 16 bits per pixel. How a pixel looks
> > like internally doesn't matter. So both RGB555 and RGB565 use fbcon-cfb16.c.
> 
> So i suppose saying fbset -depth 15 could be done to switch the fb to
> RGBA5551 mode ? 

No, -depth actually means bits-per-pixel in fbset (yes this is a bug).

> BTW, what is fbset -depth 24 supposed to do, especially if the chip only
> support 8, 16, and 32 bpp ?

Fbset should do nothing special, the fbdev should round up
fb_var_screeninfo.bpp to 32.

> should only fbset -depth 32 be supported ?

Huh?

> Also, i am experiencing some (maybe hardware) bugs, and would like to reset
> the graphic chip. Is there an existing way to do this kind of stuff via ioctl
> ore such (sure i could do it by hand under root, but i don't think fbcon/fbdev
> would be really happy with it).

You can add a fbdev specific ioctl until you fixed the bug/worked around it.

Gr{oetje,eeting}s,

						Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- ge...@li...

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
							    -- Linus Torvalds