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. 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; } -- 1.7.10.4 -- 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
