Hi Sakari, On Tuesday 29 March 2011 13:51:38 Sakari Ailus wrote: > Sakari Ailus wrote: > > Hans Verkuil wrote: > >> On Tuesday, March 29, 2011 11:35:19 Sakari Ailus wrote: > >>> Hi Hans, > >>> > >>> Many thanks for the comments! > > > > ... > > > >>> It occurred to me that an application might want to turn off a flash > >>> which has been strobed on software. That can't be done on a single > >>> button control. > >>> > >>> V4L2_CID_FLASH_SHUTDOWN? > >>> > >>> The application would know the flash strobe is ongoing before it > >>> receives a timeout fault. I somehow feel that there should be a control > >>> telling that directly. > >>> > >>> What about using a bool control for the strobe? > >> > >> It depends: is the strobe signal just a pulse that kicks off the flash, > >> or is it active throughout the flash duration? In the latter case a > >> bool makes sense, in the first case an extra button control makes > >> sense. > > > > I like buttons since I associate them with action (like strobing) but on > > the other hand buttons don't allow querying the current state. On the > > other hand, the current state isn't always determinable, e.g. in the > > absence of the interrupt line from the flash controller interrupt pin > > (e.g. N900!). > > Oh, I need to take my words back a bit. > > There indeed is a way to get the on/off status for the flash, but that > involves I2C register access --- when you read the fault registers, you > do get the state, even if the interrupt linke is missing from the > device. At least I can't see why this wouldn't work, at least on this > particular chip. > > What you can't have in this case is the event. > > So, in my opinion this suggests that a single boolean control is the way > to go. Why would an application want to turn off a flash that has been strobbed in software ? Applications should set the flash duration and then strobe it. -- Regards, Laurent Pinchart -- 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
