[Fair warning: This is pure conjecture right now.]
In
commit b8e2b0199cc377617dc238f5106352c06dcd3fa2
Author: Peter Rosin <peda@xxxxxxxxxx>
Date: Tue Jul 4 12:36:57 2017 +0200
drm/fb-helper: factor out pseudo-palette
Peter extracted the pseudo palette computation, but seems to have done
an off-by-one. I spotted that +1, but then noticed that we've passed
start++ to (now gone) setcolreg function, so it seemed to all match
up. Except post vs. pre-increment ftw.
Result is that the palette is off-by-one, and the forground color
(slot 0) ends up black, rendering a fairly unreadable console.
What baffles me is that on some systems it still seems to work
somehow, which lead us all down a wild goose chase trying to add
load_lut calls back in in various places (which was also intentionally
removed, but really doesn't seem to be the real root cause).
Fixes: b8e2b0199cc3 ("drm/fb-helper: factor out pseudo-palette")
Cc: Peter Rosin <peda@xxxxxxxxxx>
Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
Cc: Daniel Vetter <daniel.vetter@xxxxxxxxx>
Cc: Gustavo Padovan <gustavo@xxxxxxxxxxx>
Cc: Sean Paul <seanpaul@xxxxxxxxxxxx>
Cc: David Airlie <airlied@xxxxxxxx>
Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
Cc: <stable@xxxxxxxxxxxxxxx> # v4.14+
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=198123
Reported-by: Deposite Pirate <dpirate@xxxxxxxxxxxxxxx>
Reported-by: Bill Fraser <bill.fraser@xxxxxxxxx>
Cc: Deposite Pirate <dpirate@xxxxxxxxxxxxxxx>
Cc: Bill Fraser <bill.fraser@xxxxxxxxx>
Cc: Michel Dänzer <michel@xxxxxxxxxxx>
Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxxx>
---
drivers/gpu/drm/drm_fb_helper.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index 035784ddd133..1c3a200c4a10 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -1295,7 +1295,7 @@ static int setcmap_pseudo_palette(struct fb_cmap *cmap, struct fb_info *info)
mask <<= info->var.transp.offset;
value |= mask;
}
- palette[cmap->start + i] = value;
+ palette[cmap->start] = value;
}
return 0;
--
2.15.1
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