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Subject[PATCH] fbcon: prefer pan when available

Dear Andrew,

Thomas and Antonino are right; the following are better heuristics
than I had for interpreting the accel flags. please apply on top of
2.6.7-rc2-mm2

-dte

fbcon: improve heuristics to favor panning over copyarea()
thanks to pseudocode from Antonino Daplas <adaplas@hotpop.com>

Signed-off-by: David Eger <eger@havoc.gtf.org>

diff -Nru a/drivers/video/console/fbcon.c b/drivers/video/console/fbcon.c
--- a/drivers/video/console/fbcon.c Fri Jun 4 02:58:58 2004
+++ b/drivers/video/console/fbcon.c Fri Jun 4 02:58:58 2004
@@ -1469,22 +1469,26 @@
static __inline__ void updatescrollmode(struct display *p, struct fb_info *info, struct vc_data *vc)
{
int cap = info->flags;
+ int good_pan = (cap & FBINFO_HWACCEL_YPAN)
+ && divides(info->fix.ypanstep, vc->vc_font.height)
+ && info->var.yres_virtual >= 2*info->var.yres;
+ int good_wrap = (cap & FBINFO_HWACCEL_YWRAP)
+ && divides(info->fix.ywrapstep, vc->vc_font.height)
+ && divides(vc->vc_font.height, info->var.yres_virtual);
+ int reading_fast = cap & FBINFO_READS_FAST;
+ int fast_copyarea = (cap & FBINFO_HWACCEL_COPYAREA) && !(cap & FBINFO_HWACCEL_DISABLED);

- if ((cap & FBINFO_HWACCEL_COPYAREA) && !(cap & FBINFO_HWACCEL_DISABLED))
- p->scrollmode = SCROLL_ACCEL;
- else if ((cap & FBINFO_HWACCEL_YWRAP) &&
- divides(info->fix.ywrapstep, vc->vc_font.height) &&
- divides(vc->vc_font.height, info->var.yres_virtual))
- p->scrollmode = SCROLL_WRAP;
- else if ((cap & FBINFO_HWACCEL_YPAN) &&
- divides(info->fix.ypanstep, vc->vc_font.height) &&
- info->var.yres_virtual >= info->var.yres + vc->vc_font.height)
- p->scrollmode = SCROLL_PAN;
- else if (cap & FBINFO_READS_FAST)
- /* okay, we'll use software version of accel funcs... */
- p->scrollmode = SCROLL_ACCEL;
- else
- p->scrollmode = SCROLL_REDRAW;
+ if (good_wrap || good_pan) {
+ if (reading_fast || fast_copyarea)
+ p->scrollmode = good_wrap ? SCROLL_WRAP : SCROLL_PAN;
+ else
+ p->scrollmode = SCROLL_REDRAW;
+ } else {
+ if (reading_fast || fast_copyarea)
+ p->scrollmode = SCROLL_ACCEL;
+ else
+ p->scrollmode = SCROLL_REDRAW;
+ }
}

static int fbcon_resize(struct vc_data *vc, unsigned int width,
-
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