From 55f46d3887656ffb67c61cd9b44599c4cdfc65c7 Mon Sep 17 00:00:00 2001 From: wm4 Date: Wed, 13 Jan 2016 19:44:24 +0100 Subject: [PATCH] bcm2835: only allow stereo if analogue jack is selected Sending more than 2 channels to videocore while outputting to analogue mysteriously outputs heavy artifacts. So just paint it over with a hack: if analogue is explicitly selected as destination, do not reporting support for anything other than stereo. I'm not sure how to deal with the auto case (destination 0). There's probably way to retrieve this and even to listen to plug events, but I didn't find one yet, and it's probably not worth the trouble. Just don't use this setting, I guess. Unless you like noise. Changing the setting while an audio stream is active also doesn't work properly. We could probably interrupt running streams by returning ENODEV or using kernel hotplug stuff (maybe), but that also doesn't seem worth the trouble. --- sound/arm/bcm2835-ctl.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) --- a/sound/arm/bcm2835-ctl.c +++ b/sound/arm/bcm2835-ctl.c @@ -423,9 +423,16 @@ static struct cea_channel_speaker_alloca { .ca_index = 0x31, .speakers = { FRW, FLW, RR, RL, FC, LFE, FR, FL } }, }; +static int uses_analogue(bcm2835_chip_t *chip) +{ + return chip->dest == 1; +} + static int snd_bcm2835_chmap_ctl_tlv(struct snd_kcontrol *kcontrol, int op_flag, unsigned int size, unsigned int __user *tlv) { + struct snd_pcm_chmap *info = snd_kcontrol_chip(kcontrol); + bcm2835_chip_t *chip = info->private_data; unsigned int __user *dst; int count = 0; int i; @@ -442,6 +449,9 @@ static int snd_bcm2835_chmap_ctl_tlv(str int chs_bytes; int c; + if (i > 0 && uses_analogue(chip)) + break; + for (c = 0; c < 8; c++) { if (ch->speakers[c]) num_chs++; @@ -552,6 +562,8 @@ static int snd_bcm2835_chmap_ctl_put(str int matches = 1; int cur = 0; int x; + if (i > 0 && uses_analogue(chip)) + break; memset(remap, 0, sizeof(remap)); for (x = 0; x < substream->runtime->channels; x++) { int sp = ucontrol->value.integer.value[x];