diff mbox series

ALSA: usb-audio: Name feature ctl using output if input is PCM

Message ID 20240301231107.42679-1-kl@kl.wtf (mailing list archive)
State Accepted
Commit 1601cd53c7e3197181277326dbfc131d20a74e46
Headers show
Series ALSA: usb-audio: Name feature ctl using output if input is PCM | expand

Commit Message

Kenny Levinsen March 1, 2024, 11:11 p.m. UTC
When building feature controls from a unit without a name, we try to
derive a name first from the feature unit's input, then fall back to the
output terminal.

If a feature unit connects directly to a "USB Streaming" input terminal
rather than a mixer or other virtual type, the control receives the
somewhat meaningless name "PCM", even if the output had a descriptive
type such as "Headset" or "Speaker".

Here is an example of such AudioControl descriptor from a USB headset
which ends up named "PCM Playback" and is therefore not recognized as
headphones by userspace:

      AudioControl Interface Descriptor:
        bLength                12
        bDescriptorType        36
        bDescriptorSubtype      2 (INPUT_TERMINAL)
        bTerminalID             4
        wTerminalType      0x0101 USB Streaming
        bAssocTerminal          5
        bNrChannels             2
        wChannelConfig     0x0003
          Left Front (L)
          Right Front (R)
        iChannelNames           0
        iTerminal               0
      AudioControl Interface Descriptor:
        bLength                 9
        bDescriptorType        36
        bDescriptorSubtype      3 (OUTPUT_TERMINAL)
        bTerminalID             5
        wTerminalType      0x0402 Headset
        bAssocTerminal          4
        bSourceID               6
        iTerminal               0
      AudioControl Interface Descriptor:
        bLength                13
        bDescriptorType        36
        bDescriptorSubtype      6 (FEATURE_UNIT)
        bUnitID                 6
        bSourceID               4
        bControlSize            2
        bmaControls(0)     0x0002
          Volume Control
        bmaControls(1)     0x0000
        bmaControls(2)     0x0000
        iFeature                0

Other headsets and DACs I tried that used their output terminal for
naming only did so due to their input being an unnamed sidetone mixer.

Instead of always starting with the input terminal, check the type of it
first. If it seems uninteresting, invert the order and use the output
terminal first for naming.

This makes userspace recognize headsets with simple controls as
headphones, and leads to more consistent naming of playback devices
based on their outputs irrespective of sidetone mixers.

Signed-off-by: Kenny Levinsen <kl@kl.wtf>
---
 sound/usb/mixer.c | 49 +++++++++++++++++++++++++++++++++--------------
 1 file changed, 35 insertions(+), 14 deletions(-)

Comments

Takashi Iwai March 4, 2024, 8:15 a.m. UTC | #1
On Sat, 02 Mar 2024 00:11:07 +0100,
Kenny Levinsen wrote:
> 
> When building feature controls from a unit without a name, we try to
> derive a name first from the feature unit's input, then fall back to the
> output terminal.
> 
> If a feature unit connects directly to a "USB Streaming" input terminal
> rather than a mixer or other virtual type, the control receives the
> somewhat meaningless name "PCM", even if the output had a descriptive
> type such as "Headset" or "Speaker".
> 
> Here is an example of such AudioControl descriptor from a USB headset
> which ends up named "PCM Playback" and is therefore not recognized as
> headphones by userspace:
> 
>       AudioControl Interface Descriptor:
>         bLength                12
>         bDescriptorType        36
>         bDescriptorSubtype      2 (INPUT_TERMINAL)
>         bTerminalID             4
>         wTerminalType      0x0101 USB Streaming
>         bAssocTerminal          5
>         bNrChannels             2
>         wChannelConfig     0x0003
>           Left Front (L)
>           Right Front (R)
>         iChannelNames           0
>         iTerminal               0
>       AudioControl Interface Descriptor:
>         bLength                 9
>         bDescriptorType        36
>         bDescriptorSubtype      3 (OUTPUT_TERMINAL)
>         bTerminalID             5
>         wTerminalType      0x0402 Headset
>         bAssocTerminal          4
>         bSourceID               6
>         iTerminal               0
>       AudioControl Interface Descriptor:
>         bLength                13
>         bDescriptorType        36
>         bDescriptorSubtype      6 (FEATURE_UNIT)
>         bUnitID                 6
>         bSourceID               4
>         bControlSize            2
>         bmaControls(0)     0x0002
>           Volume Control
>         bmaControls(1)     0x0000
>         bmaControls(2)     0x0000
>         iFeature                0
> 
> Other headsets and DACs I tried that used their output terminal for
> naming only did so due to their input being an unnamed sidetone mixer.
> 
> Instead of always starting with the input terminal, check the type of it
> first. If it seems uninteresting, invert the order and use the output
> terminal first for naming.
> 
> This makes userspace recognize headsets with simple controls as
> headphones, and leads to more consistent naming of playback devices
> based on their outputs irrespective of sidetone mixers.
> 
> Signed-off-by: Kenny Levinsen <kl@kl.wtf>

Thanks, applied now to for-next branch.


Takashi
diff mbox series

Patch

diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c
index 409fc1164694..81256ab56835 100644
--- a/sound/usb/mixer.c
+++ b/sound/usb/mixer.c
@@ -1652,6 +1652,34 @@  static const struct usb_feature_control_info *get_feature_control_info(int contr
 	return NULL;
 }
 
+static int feature_unit_mutevol_ctl_name(struct usb_mixer_interface *mixer,
+					 struct snd_kcontrol *kctl,
+					 struct usb_audio_term *iterm,
+					 struct usb_audio_term *oterm)
+{
+	struct usb_audio_term *aterm, *bterm;
+	bool output_first;
+	int len = 0;
+
+	/*
+	 * If the input terminal is USB Streaming, we try getting the name of
+	 * the output terminal first in hopes of getting something more
+	 * descriptive than "PCM".
+	 */
+	output_first = iterm && !(iterm->type >> 16) && (iterm->type & 0xff00) == 0x0100;
+
+	aterm = output_first ? oterm : iterm;
+	bterm = output_first ? iterm : oterm;
+
+	if (aterm)
+		len = get_term_name(mixer->chip, aterm, kctl->id.name,
+				    sizeof(kctl->id.name), 1);
+	if (!len && bterm)
+		len = get_term_name(mixer->chip, bterm, kctl->id.name,
+				    sizeof(kctl->id.name), 1);
+	return len;
+}
+
 static void __build_feature_ctl(struct usb_mixer_interface *mixer,
 				const struct usbmix_name_map *imap,
 				unsigned int ctl_mask, int control,
@@ -1733,22 +1761,15 @@  static void __build_feature_ctl(struct usb_mixer_interface *mixer,
 	case UAC_FU_MUTE:
 	case UAC_FU_VOLUME:
 		/*
-		 * determine the control name.  the rule is:
-		 * - if a name id is given in descriptor, use it.
-		 * - if the connected input can be determined, then use the name
-		 *   of terminal type.
-		 * - if the connected output can be determined, use it.
-		 * - otherwise, anonymous name.
+		 * Determine the control name:
+		 * - If a name id is given in descriptor, use it.
+		 * - If input and output terminals are present, try to derive
+		 *   the name from either of these.
+		 * - Otherwise, make up a name using the feature unit ID.
 		 */
 		if (!len) {
-			if (iterm)
-				len = get_term_name(mixer->chip, iterm,
-						    kctl->id.name,
-						    sizeof(kctl->id.name), 1);
-			if (!len && oterm)
-				len = get_term_name(mixer->chip, oterm,
-						    kctl->id.name,
-						    sizeof(kctl->id.name), 1);
+			len = feature_unit_mutevol_ctl_name(mixer, kctl, iterm,
+							    oterm);
 			if (!len)
 				snprintf(kctl->id.name, sizeof(kctl->id.name),
 					 "Feature %d", unitid);