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. I'm happy with a menu control for LEDs, something like: Auto (default) Off and possibly: On Blink Although I'm not so sure we need/want these last two. It should be a control since otherwise v4l2 apps would need to add support for the LED interface just for this, whereas if it is a control it will 'just work'. I think it is up to the driver whether it wants to implement the LED interface as well. Regards, Hans > > [snip] > > > >> Reading this whole thread I have to agree that if we are going to expose > > >> camera status LEDs it would be done through the sysfs API. I think this > > >> can be done nicely for gspca based drivers (as we can put all the "crud" > > >> in the gspca core having to do it only once), but that is a low priority > > >> nice to have thingy. > > >> > > >> This does leave us with the problem of logitech uvc cams where the LED > > >> currently is exposed as a v4l2 control. > > > > > > Is it possible for the uvc driver to detect and use a LED control? That's > > > how I would expect this to work, but I know that uvc is a bit of a > > > strange beast. > > > > Unfortunately no, some uvc cameras have "proprietary" controls. The uvc > > driver knows nothing about these but offers an API to map these to v4l2 > > controls (where userspace tells it the v4l2 cid, type, min, max, etc.). > > > > Currently on logitech cameras the userspace tools if installed will map > > the led control to a private v4l2 menu control with the following options: > > On > > Off > > Auto > > Blink > > > > The cameras default to auto, where the led is turned on when video > > is being streamed and off when there is no streaming going on. > > I confirm this. If the UVC LED controls were standard the driver could expose > them through a LED-specific API. As UVC allows devices to implement private > controls, the driver needs to expose all those private controls (both LED and > non-LED) through the same API. > > -- Hans Verkuil - video4linux developer - sponsored by TANDBERG, part of Cisco -- 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
