On Mon August 13 2012 15:13:34 Hans de Goede wrote: > Hi, > > <snip> > > > 5) How to handle tuner ownership if both a video and radio node share the same > > tuner? > > > > Obvious rules: > > > > - Calling S_FREQ, S_TUNER, S_MODULATOR or S_HW_FREQ_SEEK will change owner > > or return EBUSY if streaming is in progress. > > That won't work, as there is no such thing as streaming from a radio node, There is, actually: read() for RDS data and alsa streaming (although that might be hard to detect in the case of USB audio). > I suggest we go with the simple approach we discussed at our last meeting in > your Dutch House: Calling S_FREQ, S_TUNER, S_MODULATOR or S_HW_FREQ_SEEK will > make an app the tuner-owner, and *closing* the device handle makes an app > release its tuner ownership. If an other app already is the tuner owner > -EBUSY is returned. So the ownership is associated with a filehandle? > > > - Ditto for STREAMON, read/write and polling for read/write. > > No, streaming and tuning are 2 different things, if an app does both, it > will likely tune before streaming, but in some cases a user may use a streaming > only app together with say v4l2-ctl to do the actual tuning. I think keeping > things simple here is key. Lets just treat the "tuner" and "stream" as 2 separate > entities with a separate ownership. That would work provided the ownership is associated with a filehandle. > > > - Ditto for ioctls that expect a valid tuner configuration like QUERYSTD. > > QUERY is a read only ioctl, so it should not be influenced by any ownership, nor > imply ownership. It is definitely influenced by ownership, since if the tuner is in radio mode, then it can't detect a standard. Neither is this necessarily a passive call as some (mostly older) drivers need to switch the receiver to different modes in order to try and detect the current standard. > > - Just opening a device node should *not* switch ownership. > Ack! > > > But it is not clear what to do when any of these ioctls are called: > > > > - G_FREQUENCY: could just return the last set frequency for radio or TV: > > requires that that is remembered when switching ownership. This is what > > happens today, so G_FREQUENCY does not have to switch ownership. > > Ack. > > > - G_TUNER: the rxsubchans, signal and afc fields all require ownership of > > the tuner. So in principle you would want to switch ownership when > > G_TUNER is called. On the other hand, that would mean that calling > > v4l2-ctl --all -d /dev/radio0 would change tuner ownership to radio for > > /dev/video0. That's rather unexpected. > > > > It is possible to just set rxsubchans, signal and afc to 0 if the device > > node doesn't own the tuner. I'm inclined to do that. > > Right, G_TUNER should not change ownership, if the tuner is currently in radio > mode and a G_TUNER is done on the video node just 0 out the fields which we cannot > fill with useful info. > > > - Should closing a device node switch ownership? E.g. if nobody has a radio > > device open, should the tuner switch back to TV mode automatically? I don't > > think it should. > > +1 on delaying the mode switch until it is actually necessary to switch mode. > > > - How about hybrid tuners? > > No opinion. Regards, Hans -- 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
