[PATCH] [RFC] ALSA: hda: Fix the control element identification for multiple codecs

[Jaroslav Kysela]

[This is a RFC for the discussion]

Some motherboards have multiple HDA codecs connected to the serial bus.
The current code may create multiple mixer controls with the almost
identical identification.

The current code use id.device field from the control element structure
to store the codec address to avoid such clashes for multiple codecs.
Unfortunately, the user space do not handle this correctly. For mixer
controls, only name and index are used for the identifiers.

This patch fixes this problem to compose the index using the codec
address as an offset in case, when the control already exists. It is
really unlikely that one codec will create 10 similar controls.

This patch adds new kernel module parameter 'ctl_dev_id' to allow
select the old behaviour, too.

BugLink: https://github.com/alsa-project/alsa-lib/issues/294
BugLink: https://github.com/alsa-project/alsa-lib/issues/205
Fixes: 54d174031576 ("[ALSA] hda-codec - Fix connection list parsing")
Fixes: 1afe206ab699 ("ALSA: hda - Try to find an empty control index when it's occupied")
Signed-off-by: Jaroslav Kysela <perex at perex.cz>

--

Discussion:

There are several possibilities to handle the old behaviour - a kernel
module parameter (proposed), a kernel configuration option or drop
the old behaviour completely.
---
 include/sound/hda_codec.h      |  1 +
 sound/pci/hda/hda_codec.c      | 13 ++++++++++---
 sound/pci/hda/hda_controller.c |  1 +
 sound/pci/hda/hda_controller.h |  1 +
 sound/pci/hda/hda_intel.c      |  5 +++++
 5 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/include/sound/hda_codec.h b/include/sound/hda_codec.h
index eba23daf2c29..bbb7805e85d8 100644
--- a/include/sound/hda_codec.h
+++ b/include/sound/hda_codec.h
@@ -259,6 +259,7 @@ struct hda_codec {
 	unsigned int relaxed_resume:1;	/* don't resume forcibly for jack */
 	unsigned int forced_resume:1; /* forced resume for jack */
 	unsigned int no_stream_clean_at_suspend:1; /* do not clean streams at suspend */
+	unsigned int ctl_dev_id:1; /* old control element id build behaviour */
 
 #ifdef CONFIG_PM
 	unsigned long power_on_acct;
diff --git a/sound/pci/hda/hda_codec.c b/sound/pci/hda/hda_codec.c
index edd653ece70d..8f20abc036bf 100644
--- a/sound/pci/hda/hda_codec.c
+++ b/sound/pci/hda/hda_codec.c
@@ -3390,7 +3390,12 @@ int snd_hda_add_new_ctls(struct hda_codec *codec,
 			kctl = snd_ctl_new1(knew, codec);
 			if (!kctl)
 				return -ENOMEM;
-			if (addr > 0)
+			/* Do not use the id.device field for MIXER elements.
+			 * This field is for real device numbers (like PCM) but codecs
+			 * are hidden components from the user space view (unrelated
+			 * to the mixer element identification).
+			 */
+			if (addr > 0 && codec->ctl_dev_id)
 				kctl->id.device = addr;
 			if (idx > 0)
 				kctl->id.index = idx;
@@ -3401,9 +3406,11 @@ int snd_hda_add_new_ctls(struct hda_codec *codec,
 			 * the codec addr; if it still fails (or it's the
 			 * primary codec), then try another control index
 			 */
-			if (!addr && codec->core.addr)
+			if (!addr && codec->core.addr) {
 				addr = codec->core.addr;
-			else if (!idx && !knew->index) {
+				if (!codec->ctl_dev_id)
+					idx += 10 * addr;
+			} else if (!idx && !knew->index) {
 				idx = find_empty_mixer_ctl_idx(codec,
 							       knew->name, 0);
 				if (idx <= 0)
diff --git a/sound/pci/hda/hda_controller.c b/sound/pci/hda/hda_controller.c
index 0ff286b7b66b..083df287c1a4 100644
--- a/sound/pci/hda/hda_controller.c
+++ b/sound/pci/hda/hda_controller.c
@@ -1231,6 +1231,7 @@ int azx_probe_codecs(struct azx *chip, unsigned int max_slots)
 				continue;
 			codec->jackpoll_interval = chip->jackpoll_interval;
 			codec->beep_mode = chip->beep_mode;
+			codec->ctl_dev_id = chip->ctl_dev_id;
 			codecs++;
 		}
 	}
diff --git a/sound/pci/hda/hda_controller.h b/sound/pci/hda/hda_controller.h
index f5bf295eb830..8556031bcd68 100644
--- a/sound/pci/hda/hda_controller.h
+++ b/sound/pci/hda/hda_controller.h
@@ -124,6 +124,7 @@ struct azx {
 	/* HD codec */
 	int  codec_probe_mask; /* copied from probe_mask option */
 	unsigned int beep_mode;
+	bool ctl_dev_id;
 
 #ifdef CONFIG_SND_HDA_PATCH_LOADER
 	const struct firmware *fw;
diff --git a/sound/pci/hda/hda_intel.c b/sound/pci/hda/hda_intel.c
index 87002670c0c9..2ef57dfa81f1 100644
--- a/sound/pci/hda/hda_intel.c
+++ b/sound/pci/hda/hda_intel.c
@@ -119,6 +119,7 @@ static bool beep_mode[SNDRV_CARDS] = {[0 ... (SNDRV_CARDS-1)] =
 					CONFIG_SND_HDA_INPUT_BEEP_MODE};
 #endif
 static bool dmic_detect = 1;
+static bool ctl_dev_id[SNDRV_CARDS];
 
 module_param_array(index, int, NULL, 0444);
 MODULE_PARM_DESC(index, "Index value for Intel HD audio interface.");
@@ -157,6 +158,8 @@ module_param(dmic_detect, bool, 0444);
 MODULE_PARM_DESC(dmic_detect, "Allow DSP driver selection (bypass this driver) "
 			     "(0=off, 1=on) (default=1); "
 		 "deprecated, use snd-intel-dspcfg.dsp_driver option instead");
+module_param_array(ctl_dev_id, bool, NULL, 0444);
+MODULE_PARM_DESC(ctl_dev_id, "Use control device identifier (based on codec address).");
 
 #ifdef CONFIG_PM
 static int param_set_xint(const char *val, const struct kernel_param *kp);
@@ -2278,6 +2281,8 @@ static int azx_probe_continue(struct azx *chip)
 	chip->beep_mode = beep_mode[dev];
 #endif
 
+	chip->ctl_dev_id = ctl_dev_id[dev];
+
 	/* create codec instances */
 	if (bus->codec_mask) {
 		err = azx_probe_codecs(chip, azx_max_codecs[chip->driver_type]);
-- 
2.39.0