ALSA: scarlett2: Allow for interfaces without per-channel volume

Currently-supported interfaces with a mixer have per-channel volume
controls, but this changes in Gen 4. Add a check so that the Playback
Volume and associated controls don't get created unless the
SCARLETT2_CONFIG_LINE_OUT_VOLUME config item is present.

Signed-off-by: Geoffrey D. Bennett <g@b4.vu>
Link: https://lore.kernel.org/r/30f68cb311e27f2cc1351cb846218f7248a90263.1703444932.git.g@b4.vu
Signed-off-by: Takashi Iwai <tiwai@suse.de>

diff --git a/sound/usb/mixer_scarlett2.c b/sound/usb/mixer_scarlett2.c
index 0d86c41432fc42601ec980278dbe7f470c32fa31..95f6f1454fbfbe130728194ce12f28b9a3a1c9ba 100644 (file)
--- a/sound/usb/mixer_scarlett2.c
+++ b/sound/usb/mixer_scarlett2.c
@@ -3726,6 +3726,13 @@ static int scarlett2_add_line_out_ctls(struct usb_mixer_interface *mixer)
                        return err;
        }
 
+       /* Remaining controls are only applicable if the device
+        * has per-channel line-out volume controls.
+        */
+       if (!scarlett2_has_config_item(private,
+                                      SCARLETT2_CONFIG_LINE_OUT_VOLUME))
+               return 0;
+
        /* Add volume controls */
        for (i = 0; i < private->num_line_out; i++) {
                int index = line_out_remap(private, i);
@@ -4569,7 +4576,6 @@ static int scarlett2_read_configs(struct usb_mixer_interface *mixer)
 {
        struct scarlett2_data *private = mixer->private_data;
        int err, i;
-       s16 sw_vol[SCARLETT2_ANALOGUE_MAX];
 
        if (scarlett2_has_config_item(private, SCARLETT2_CONFIG_MSD_SWITCH)) {
                err = scarlett2_usb_get_config(
@@ -4608,41 +4614,47 @@ static int scarlett2_read_configs(struct usb_mixer_interface *mixer)
        if (err < 0)
                return err;
 
-       /* read SW line out volume */
-       err = scarlett2_usb_get_config(
-               mixer, SCARLETT2_CONFIG_LINE_OUT_VOLUME,
-               private->num_line_out, &sw_vol);
-       if (err < 0)
-               return err;
-
-       for (i = 0; i < private->num_line_out; i++)
-               private->vol[i] = clamp(
-                       sw_vol[i] + SCARLETT2_VOLUME_BIAS,
-                       0, SCARLETT2_VOLUME_BIAS);
+       if (scarlett2_has_config_item(private,
+                                     SCARLETT2_CONFIG_LINE_OUT_VOLUME)) {
+               s16 sw_vol[SCARLETT2_ANALOGUE_MAX];
 
-       /* read SW mute */
-       err = scarlett2_usb_get_config(
-               mixer, SCARLETT2_CONFIG_MUTE_SWITCH,
-               private->num_line_out, &private->mute_switch);
-       if (err < 0)
-               return err;
+               /* read SW line out volume */
+               err = scarlett2_usb_get_config(
+                       mixer, SCARLETT2_CONFIG_LINE_OUT_VOLUME,
+                       private->num_line_out, &sw_vol);
+               if (err < 0)
+                       return err;
 
-       for (i = 0; i < private->num_line_out; i++)
-               private->mute_switch[i] =
-                       !!private->mute_switch[i];
+               for (i = 0; i < private->num_line_out; i++)
+                       private->vol[i] = clamp(
+                               sw_vol[i] + SCARLETT2_VOLUME_BIAS,
+                               0, SCARLETT2_VOLUME_BIAS);
 
-       /* read SW/HW switches */
-       if (scarlett2_has_config_item(private,
-                                     SCARLETT2_CONFIG_SW_HW_SWITCH)) {
+               /* read SW mute */
                err = scarlett2_usb_get_config(
-                       mixer, SCARLETT2_CONFIG_SW_HW_SWITCH,
-                       private->num_line_out, &private->vol_sw_hw_switch);
+                       mixer, SCARLETT2_CONFIG_MUTE_SWITCH,
+                       private->num_line_out, &private->mute_switch);
                if (err < 0)
                        return err;
 
                for (i = 0; i < private->num_line_out; i++)
-                       private->vol_sw_hw_switch[i] =
-                               !!private->vol_sw_hw_switch[i];
+                       private->mute_switch[i] =
+                               !!private->mute_switch[i];
+
+               /* read SW/HW switches */
+               if (scarlett2_has_config_item(private,
+                                             SCARLETT2_CONFIG_SW_HW_SWITCH)) {
+                       err = scarlett2_usb_get_config(
+                               mixer, SCARLETT2_CONFIG_SW_HW_SWITCH,
+                               private->num_line_out,
+                               &private->vol_sw_hw_switch);
+                       if (err < 0)
+                               return err;
+
+                       for (i = 0; i < private->num_line_out; i++)
+                               private->vol_sw_hw_switch[i] =
+                                       !!private->vol_sw_hw_switch[i];
+               }
        }
 
        err = scarlett2_update_volumes(mixer);