Em 13-09-2010 10:49, Andy Walls escreveu: > On Mon, 2010-09-13 at 08:45 -0300, Mauro Carvalho Chehab wrote: >> Em 13-09-2010 05:06, Hans Verkuil escreveu: >>> On Monday, September 13, 2010 09:04:18 Laurent Pinchart wrote: >>>> Hi Hans, >>>> >>>> On Thursday 09 September 2010 13:48:58 Hans de Goede wrote: >>>>> On 09/09/2010 03:29 PM, Hans Verkuil wrote: >>>>>>> On 09/09/2010 08:55 AM, Peter Korsgaard wrote: >>>>>>>> "Hans" == Hans Verkuil<hverkuil@xxxxxxxxx> writes: >>>>>>>> >>>>>>>> I originally was in favor of controlling these through v4l as well, but >>>>>>>> people made some good arguments against that. The main one being: why >>>>>>>> would you want to show these as a control? What is the end user supposed >>>>>>>> to do with them? It makes little sense. >>>> >>>> Status LEDs reflect in glasses, making annoying color dots on webcam pictures. >>>> That's why Logitech allows to turn the status LED off on its webcams. >>> >>> That's a really good argument. I didn't think of that one. >> >> There's one difference between illuminators and leds and anything else that we use >> currently via CTRL interface: all other controls affects just an internal hardware >> capability that are not visible to the user, nor can cause any kind of damage or >> annoyance. >> >> On the other hand, a LED and an illuminator that an application may forget to turn >> off could be very annoying, and may eventually reduce the lifecycle or a device (in >> the case of non-LED illuminators, for example). > > Yes, I can appreciate that. On driver unload and suspend that should > certainly be the case for illuminators. > > However, I don't think that's a good idea for final close on a file > descriptor though. That's a departure from normal V4L2 behavior. This doesn't seem to be a good reason. Keeping a LED after its usage is annoying to the user, can cause damage on devices (reduce lifetime) and can draw lots of power from the batteries (on battery-powered devices). > For a USB connected device, turning off the illuminator after the fact > is simple, if the user has no other recourse: unplug the device. :) Try to unplug the flash led on your cell phone ;) >> So, a special treatment seems to be required for both cases: if the application that >> changed the LED or illuminator to ON dies or closes, the LED/illuminator should be >> turned off by the driver. > > That will break cases like these: > > $ v4l2-ctl -d /dev/video0 -c illuminator_2=1 > $ (command to run app that doesn't present all controls, e.g. cheese) True, but it may have an alternative syntax for it, like: v4l2-ctl -d /dev/video0 -c illuminator_2=1 --run cheese [<args>] This way, if cheese or v4l2-ctl abends, the illuminator will be turned off. Of course, we'll likely need to have a flag visible on userspace, to say that such control resets to an "off" state when the application dies, to avoid someone to use it like: v4l2-ctl -d /dev/video0 -c illuminator_2=1 Cheers, Mauro -- 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
