Re: [Linux-fbdev-devel] fb_imageblit semantic

[Antonino D. <ad...@po...>]

On Mon, 2003-03-17 at 18:40, Petr Vandrovec wrote:
> On 17 Mar 03 at 11:31, Geert Uytterhoeven wrote:
> > On 17 Mar 2003, Antonino Daplas wrote:
> > > As Geert said, it's not just trivial, but logical to split fb_imageblit
> > > into two.
> > 
> > So, are we gonna split it? This will also make hardware acceleration support
> > more clean. E.g. most sbus drivers do color expansion in hardware, and fall
> > back to cfb_imageblit() for the logo.
> > 

It's up to James, though I vote for it.  And I don't think any driver
has accelerated versions of fb_imageblit for the logo, since any
performance gained is probably minimal and it will involve too much work
for something that's going to be done only once.
  
> > > > OK, so rule is that if depth=0, input is 1bpp with palette in bgcol/fgcol,
> > > > while if depth != 0, then palette is in info->pseudo_palette ?
> > > 
> > > Yes.  You can also say that if image->depth != var->bits_per_pixel, do
> > > color expansion or reduction, whatever the case may be.
> > 
> > Hmmm... Note that image->depth can be larger than 8, while the image data is
> > still 8-bit. This is an inconsistency.

I was thinking that if image->depth=8 and var->bits_per_pixel=4, then
the driver is in danger of going out of bounds when referring to the
pseudo_palette.  But I forgot that the fb_show_logo() takes care of
avoiding that :-)  And yes, current usage of image->depth is pretty
inconsistent and basically useless.

> 
> image->depth for logo must change to 8. Or remove depth completely after
> splitting imageblit to paintchar & paintlogo, as currently depth is
> useless anyway: target format is defined by framebuffer layout, not
> by image->depth, and source format is hardwired to the code.

You're correct.  If it's going to be split, image->depth becomes
redundant.

Tony