On Sun, 19 Dec 2010, Adam Baker wrote: > On Sunday 19 Dec 2010, Theodore Kilgore wrote: > > Finally, one concern that I have in the back of my mind is the question of > > control settings for a camera which streams in bulk mode and requires the > > setup of a workqueue. The owner of the camera says that he has > > "encountered no problems" with running the two controls mentioned above. > > Clearly, that is not a complete answer which overcomes all possible > > objections. Rather, things are OK if and only if we can ensure that these > > controls can be run only while the workqueue that does the streaming is > > inactive. Somehow, I suspect that the fact that a sensible user would only > > run such commands at camera setup is an insufficient guarantee that no > > problems will ever be encountered. > > > > So, as I said, the question of interaction of a control and a workqueue is > > another problem interesting little problem. Your thoughts on this > > interesting little problem would be appreciated. > > I don't think you can assume a user won't try to adjust such controls while > streaming - what I said, actually if I had one I'd certainly want to try swapping the control while > streaming to see if I could see any affect on the output. Yeah, I tell people that I like to see if I can hook things together and make something go "bang." Or, that I do research about locating that elusive magic smoke in the hardware, which makes it run. So maybe I would try that too, just for the pure hell of it. But I did say something about a "sensible user"? Neither of us, apparently. And come down to it, if one cannot trust you, and cannot trust me, as much work as we did together, then nobody can be trusted at all. :-} Even though sq905.c > doesn't have any controls on the camera it still ended up needing the locking > that would make this safe. See the header comment on sq905_dostream If the controls are locked while the workqueue is doing the streaming, then probably that does fix the problem? Most likely, that is the simplest thing to do. Theodore Kilgore -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
