From 785b6f29a795f109685f286b91e0250c206fbffb Mon Sep 17 00:00:00 2001
From: Takashi Iwai <tiwai@suse.de>
Date: Wed, 23 Jun 2021 02:30:49 +0930
Subject: [PATCH] ALSA: usb-audio: scarlett2: Fix wrong resume call
Git-commit: 785b6f29a795f109685f286b91e0250c206fbffb
Patch-mainline: v5.14-rc1
References: git-fixes

The current way of the scarlett2 mixer code managing the
usb_mixer_elem_info object is wrong in two ways: it passes its
internal index to the head.id field, and the val_type field is
uninitialized.  This ended up with the wrong execution at the resume
because a bogus unit id is passed wrongly.  Also, in the later code
extensions, we'll have more mixer elements, and passing the index will
overflow the unit id size (of 256).

This patch corrects those issues.  It introduces a new value type,
USB_MIXER_BESPOKEN, which indicates a non-standard mixer element, and
use this type for all scarlett2 mixer elements, as well as
initializing the fixed unit id 0 for avoiding the overflow.

Tested-by: Geoffrey D. Bennett <g@b4.vu>
Signed-off-by: Geoffrey D. Bennett <g@b4.vu>
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/49721219f45b7e175e729b0d9d9c142fd8f4342a.1624379707.git.g@b4.vu
Signed-off-by: Takashi Iwai <tiwai@suse.de>

---
 sound/usb/mixer.c               | 3 +++
 sound/usb/mixer.h               | 1 +
 sound/usb/mixer_scarlett_gen2.c | 7 ++++++-
 3 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c
index 4ea4875abdf8..30b3e128e28d 100644
--- a/sound/usb/mixer.c
+++ b/sound/usb/mixer.c
@@ -3606,6 +3606,9 @@ static int restore_mixer_value(struct usb_mixer_elem_list *list)
 	struct usb_mixer_elem_info *cval = mixer_elem_list_to_info(list);
 	int c, err, idx;
 
+	if (cval->val_type == USB_MIXER_BESPOKEN)
+		return 0;
+
 	if (cval->cmask) {
 		idx = 0;
 		for (c = 0; c < MAX_CHANNELS; c++) {
diff --git a/sound/usb/mixer.h b/sound/usb/mixer.h
index e5a01f17bf3c..ea41e7a1f7bf 100644
--- a/sound/usb/mixer.h
+++ b/sound/usb/mixer.h
@@ -55,6 +55,7 @@ enum {
 	USB_MIXER_U16,
 	USB_MIXER_S32,
 	USB_MIXER_U32,
+	USB_MIXER_BESPOKEN,	/* non-standard type */
 };
 
 typedef void (*usb_mixer_elem_dump_func_t)(struct snd_info_buffer *buffer,
diff --git a/sound/usb/mixer_scarlett_gen2.c b/sound/usb/mixer_scarlett_gen2.c
index dde008ea21d7..c4689c401d6e 100644
--- a/sound/usb/mixer_scarlett_gen2.c
+++ b/sound/usb/mixer_scarlett_gen2.c
@@ -1136,10 +1136,15 @@ static int scarlett2_add_new_ctl(struct usb_mixer_interface *mixer,
 	if (!elem)
 		return -ENOMEM;
 
+	/* We set USB_MIXER_BESPOKEN type, so that the core USB mixer code
+	 * ignores them for resume and other operations.
+	 * Also, the head.id field is set to 0, as we don't use this field.
+	 */
 	elem->head.mixer = mixer;
 	elem->control = index;
-	elem->head.id = index;
+	elem->head.id = 0;
 	elem->channels = channels;
+	elem->val_type = USB_MIXER_BESPOKEN;
 
 	kctl = snd_ctl_new1(ncontrol, elem);
 	if (!kctl) {
-- 
2.26.2