On Thu, Nov 06, 2014 at 12:35:48PM +0100, Andrzej Hajda wrote: > Exynos DSI driver uses DSI bus attach/detach callbacks to implement > panel hotplug mechanism. The patch moves panel attachment code > from .detect callback to DSI bus callbacks. It makes the code > simpler and more straightforward. > The patch removes also redundant and lock unprotected dpms_off call > from unbind code. > > Signed-off-by: Andrzej Hajda <a.hajda@xxxxxxxxxxx> > --- > Hi, > > This patch simplifies drm part of hotplug mechanism in dsi attach/detach callbacks. > It also fixes minor bug with unprotected dpms_off call, which is unneccesary anyway. > > But the main reason I have looked at this code again is to show that > we do not need zombie panels, we can kill panels properly if we have hot plug/unplug > callbacks. And it is quite simple: we just need to take mode_config.mutex locks > to synchronize dsi callbacks with drm, nothing more. > It works nicely because of two things: > - panel callbacks are called always under this lock, > - callbacks are installed after drmdev creation and deinstalled before drmdev destroy - > this way we assure drmdev is always present in callbacks. Again, something like what you propose is going to work only for DSI devices. What we need is a solution that works for all other types of panels, too. This is even more important when we consider bridges because they are less likely to be on a DSI bus. Thierry
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