Messages in this thread | | | From | Doug Anderson <> | Date | Fri, 23 Apr 2021 09:46:57 -0700 | Subject | Re: [PATCH v4 27/27] drm/panel: panel-simple: Prepare/unprepare are refcounted, not forced |
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Hi,
On Fri, Apr 16, 2021 at 3:41 PM Douglas Anderson <dianders@chromium.org> wrote: > > Historically simple-panel had code to make sure that if prepare() was > called on an already-prepared panel that it was a no-op. Similarly if > unprepare() was called on an already-unprepared panel it was also a > no-op. Essentially it means that these functions always "forced" the > value to be whatever the caller wanted it to be. You can see that the > forcing behavior dates back at least as far as 2014 by looking at > commit 613a633e7a56 ("drm/panel: simple: Add proper definition for > prepare and unprepare"). > > Apparently the code supporting the historical behavior may not be > needed [1] and prepare() / unprepare() are supposed to be > balanced. Let's try removing it and see if anyone breaks! If they do > then we can have a debate about whether we should change that code or > revert this patch. :-) If nobody breaks then we've nicely saved a few > lines of code and some complexity. > > [1] https://lore.kernel.org/r/YHePsQgqOau1V5lD@pendragon.ideasonboard.com > > Suggested-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> > Signed-off-by: Douglas Anderson <dianders@chromium.org> > --- > > (no changes since v1) > > drivers/gpu/drm/panel/panel-simple.c | 14 -------------- > 1 file changed, 14 deletions(-)
So it turns out that when looking at panel_simple_remove() I already found a case that's not necessarily refcounting. There I see drm_panel_unprepare() just simply hardcoded, but (as I understand it) there's no reason to believe that the panel has been prepared at remove() time. Yes, I could fix panel_simple_remove() but instead, for now, I think I'm going to drop this patch from the series. If someone wants to pick it up then I certainly won't object, but for now keeping the way things are seems the best way to keep from getting shouted at.
-Doug
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