On Tue, Jan 13, 2015 at 12:08:11AM +0100, Daniel Vetter wrote: > On Fri, Jan 9, 2015 at 1:50 PM, Jani Nikula <[email protected]> wrote: > > I have a slightly uneasy feeling about handing out drm_panel pointers > > (both from here and of_drm_find_panel) without refcounting. If the panel > > driver gets removed, whoever called the find functions will have a > > dangling pointer. I supposed this will be discussed on drm-devel. > > There's been some discussion already about exactly this problem (but > with drm bridges) with Thierry and some other people. Cc'ed them all > hopefully. Especially when the panel/bridge is a separate driver > there's imo indeed an issue.
I posted patches some time ago to create a generic registry to do the actual ref-counting[0]. It didn't seem to be very well received by Greg for the core, so perhaps we could test-drive it in DRM first for panels and bridges and once it's matured a bit it could still be promoted to the driver core, or maybe lib/. The difficult part about it is that while reference counting gives you the benefit of keeping a valid pointer around, you may still want to have a method of getting notified of the panel going away. I've thought a bit about that and I think we could probably integrate that into the registry, since that will notice anyway. Thierry [0]: http://www.spinics.net/linux/lists/kernel/msg1859333.html
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