Re: [PATCH] smart blitter usage for scrolling

["Antonino A. Daplas" <adaplas@gmail.com>]

On Thu, 2007-05-10 at 13:50 +0800, Antonino A. Daplas wrote:
> On Thu, 2007-05-10 at 07:40 +0200, Krzysztof Helt wrote:
> > Dnia 9-05-2007 o godz. 16:19 Antonino A. Daplas napisał(a):
> > > This sounds quite logical to me.  However, I would rather that 
> > you
> > > create a new scrolling mode (ie SCROLL_MOVE_REDRAW and
> > > SCROLL_WRAP_REDRAW). Then create a new FBINFO_HWACCEL flag that 
> > will
> > > enable SCROLL_PAN/WRAP_MOVE_REDRAW and perhaps another one that 
> > will
> > > enable MERGE_BLIT.
> > > 
> > 
> > I understand that you want creating a new flag instead of ifdefs 
> > but this new method should not be much slower in the worst case 
> > and much faster on average. I would rather consider replacing the 
> > existing SCROLL_MOVE mode (so no ifdefs after some 
> > experimental/test period).
> > Also, the capabilities of hardware for the new method are exactly 
> > the same as for the old SCROLL_MOVE. Every time the 
> > HWACCEL_COPYAREA is selected the new scroll method should also be 
> > selected. The new HWACCEL flag seems to be alwyas a copy of 
> > HWACCEL_COPYAREA flag.
> > 
> 
> If you think that this can be a drop-in replacement for the old one,
> then let's do just that (replace the old code) and have it tested in the
> -mm tree.
> 
> > The MERGE_BLITS is a different story but my suspection is that 
> > does not give any real benefit (in the few % range plus or minus) 
> > and could be dropped completely. I left it to allow members of 
> > this list testing and return a feedback. If my supection is true 
> > the whole MERGE_BLITS can be dropped to simplify the code.
> > 
> 
> Yeah, even without the #ifdefs, the code is quite ugly.
> 
> Okay, let's go for the simplest, cleanest and clearest code then.
> 

BTW, it is indeed possible to have a blit engine that is so fast that
doing a single, dumb blit may be more efficient that doing multiple,
intelligent blits.  Thus, a new scrolling mode might be preferable over
a drop-in replacement, but I will leave this decision to you.

Tony


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