Em Mon, 25 Mar 2013 12:32:31 +0100 Hans Verkuil <hverkuil@xxxxxxxxx> escreveu: > While testing the au0828 driver overhaul patch series: > > http://patchwork.linuxtv.org/patch/17576/ > > I discovered that the signal strength as reported by VIDIOC_G_TUNER was > always 0. Initially I thought it was related to the i2c gate, but after > testing some more that turned out to be wrong, although it did gave me the > clue that it was related to the order in which subdevs were called. If > the g_tuner op of au8522 was called before that of tuner-core, then it would > fail, if the order was the other way around then it would work. > > Some digging in tuner-core clarified it: if the has_signal callback is set, > then tuner-core would call 'vt->signal = analog_ops->has_signal(&t->fe);'. > But has_signal is always filled in, even if the frontend doesn't implement > get_rf_strength, as is the case for the xc5000. And in that case vt->signal > is overwritten with 0. > > Solution: don't set the has_signal callback if get_rf_strength is not > supported. Ditto for get_afc. It looks OK to me. > > Regards, > > Hans > > -------- patch ---------- > If the tuner frontend does not support get_rf_strength, then don't set > the has_signal callback. Ditto for get_afc. > > Both callbacks overwrite the signal and afc fields of struct v4l2_tuner > but that should only happen if the tuner can actually detect this. If > it can't, then it should leave those fields alone so other subdevices > can try and detect the signal/afc. > > This fixes the bug where the au8522 detected a signal and then tuner-core > overwrote it with 0 since the xc5000 tuner does not support get_rf_strength. > > Signed-off-by: Hans Verkuil <hans.verkuil@xxxxxxxxx> > --- > drivers/media/v4l2-core/tuner-core.c | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/drivers/media/v4l2-core/tuner-core.c b/drivers/media/v4l2-core/tuner-core.c > index f775768..dd8a803 100644 > --- a/drivers/media/v4l2-core/tuner-core.c > +++ b/drivers/media/v4l2-core/tuner-core.c > @@ -253,7 +253,7 @@ static int fe_set_config(struct dvb_frontend *fe, void *priv_cfg) > > static void tuner_status(struct dvb_frontend *fe); > > -static struct analog_demod_ops tuner_analog_ops = { > +static const struct analog_demod_ops tuner_analog_ops = { > .set_params = fe_set_params, > .standby = fe_standby, > .has_signal = fe_has_signal, > @@ -453,6 +453,11 @@ static void set_type(struct i2c_client *c, unsigned int type, > memcpy(analog_ops, &tuner_analog_ops, > sizeof(struct analog_demod_ops)); > > + if (fe_tuner_ops->get_rf_strength == NULL) > + analog_ops->has_signal = NULL; > + if (fe_tuner_ops->get_afc == NULL) > + analog_ops->get_afc = NULL; > + > } else { > t->name = analog_ops->info.name; > } -- 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
