On Wed, 06 Feb 2013, Tomi Valkeinen <tomi.valkeinen@xxxxxx> wrote: >> 6. Miscellaneous >> ---------------- >> >> - If the OMAP3 DSS driver is used as a model for the DSI support >> implementation, Daniel Vetter requested the DSI bus lock semaphore to be >> killed as it prevents lockdep from working correctly (reference needed ;-)). [...] > As for the semaphore, sure, it can be removed, although I'm not aware of > this lockdep problem. If there's a problem it should be fixed in any case. The problem is that lockdep does not support semaphores out of the box. I'm not sure how hard it would be to manually lockdep annotate the bus lock, and whether it would really work. In any case, as I think we learned in the past, getting locking right in a DSI command mode panel driver with an asynchronous update callback, DSI bus lock, and a driver data specific mutex can be a PITA. Lockdep would be extremely useful there. AFAICS simply replacing the semaphore with a mutex would work for all other cases except DSI command mode display update, unless you're prepared to wait in the call until the next tearing effect interrupt plus framedone. Which would suck. I think you and I have talked about this part in the past... BR, Jani. _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/dri-devel
