ALSA: usb-audio: scarlett2: Fix wrong resume call

commit 785b6f29a795f109685f286b91e0250c206fbffb upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c
index cf0585053a957c2d600f70ab102e92cc8e01eacf..8e11582fbae984f448def61142190d3798a73225 100644 (file)
--- a/sound/usb/mixer.c
+++ b/sound/usb/mixer.c
@@ -3631,6 +3631,9 @@ 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 c29e27ac43a7a297d41c3a2a720d8172099a1cd2..6d20ba7ee88fdeabde51a95e069f8ec8169a58c3 100644 (file)
--- 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 9a98b0c048e33daf6fc5c6342d7ce58bb40f0373..97e72b3e06c2663cf6982bf436d11f16e6d388ed 100644 (file)
--- a/sound/usb/mixer_scarlett_gen2.c
+++ b/sound/usb/mixer_scarlett_gen2.c
@@ -949,10 +949,15 @@ 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) {