On Fri September 28 2012 17:30:05 Mauro Carvalho Chehab wrote: > Em Fri, 28 Sep 2012 16:21:35 +0200 > Hans Verkuil <hverkuil@xxxxxxxxx> escreveu: > > > On Fri September 28 2012 14:43:32 Hans Verkuil wrote: > > > Hi Antti, > > > > > > Mauro asked me to look into LNA as well, in particular how this could be done > > > on the analog side as well. > > Thanks for that! > > > > > > > While reading through this patch I noticed that the new property was added to > > > dtv_property_process_set, but not to dtv_property_process_get. Can you look > > > into that and add 'get' support for this property? > > > > It's a sign of insanity when you start replying to your own email, but so > > be it :-) > > :) > > > > > I've been thinking how this can be implemented in such a way that it works > > well in all the various board/tuner configurations. > > > > First, the property should be cached in dtv_frontend_properties, that way > > tuners with a built-in LNA can use it. The initial value should be AUTO, > > I guess. > > > > The property_process_set code changes to: > > > > case DTV_LNA: > > if (fe->ops.set_lna) > > r = fe->ops.set_lna(fe, tvp->u.data); > > if (!r) > > c->lna = tvp->u.data; > > break; > > > > Tuners can now check the c->lna value when set_params is called and take the > > appropriate steps if they have a built-in LNA. > > > > To be able to access the LNA from the V4L2 side you would need to add two > > new tuner ops in include/media/v4l2-subdev.h: > > > > int (*g_lna)(struct v4l2_subdev *sd, u32 *lna); > > int (*s_lna)(struct v4l2_subdev *sd, u32 lna); > > > > The tuner-core.c driver can implement these ops to get and set c->lna accordingly. > > > > A menu control would be needed to actually change the LNA. > > > > The code that handles that control would have to call a board-specific function > > if necessary (if the LNA is on the board), and call the tuner's s_lna op otherwise. > > > > Makes sense. > > > > The only question is whether the digital and analog APIs should share the same > > LNA setting or keep different LNA states for each. > > > > So if I call DTV_LNA to set the LNA, and then check the LNA control value from V4L2, > > should the two match? Or should we keep separate states and whenever you select > > digital or analog mode the LNA is updated with the corresponding LNA value for that > > mode. > > > > The latter is a bit more work (struct analog_parameters should probably be extended > > with an LNA value), but I do think it is a cleaner solution. > > I think they both should share the same LNA state, as this depends on the physical > connection (e. g. if the antenna has LNA; if the signal reception is weak or strong > with that particular antenna). > > > I am not sure if the LNA work on the analog side should be done without having > > hardware that actually uses it, but at least the LNA support on the digital side > > should be done in such a way that it can be extended for analog as well. > > There are several saa7134 hardware with LNA support. I have one of such boards > here, although never needed to dig into the LNA stuff on it. I'll wait until Antti makes the necessary changes on the digital side, after that I'll see if I can make a patch for the analog part, and post that. There is an outside chance that I have a board with an LNA as well: for ivtv there were issues with a Samsung TCPN 2121P30A tuner where the LNA had to be turned on or off manually (it should have been automatic but due to a hardware bug that didn't work). This was never supported in ivtv, but this would make a good test case. The only problem is that I don't know if I still have that card or if I gave it to Andy. I think it went to him, actually. 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
