[PATCH] HID: input: map System Microphone Mute LED

[ait <ait@ait.place>]

From: Jonathan Jansen <jonathanjansen@ait.place>

HUTRR110 (approved 2022, part of HID Usage Tables since v1.4) defines:

  Generic Desktop (0x01)  0xa9  System Microphone Mute  OOC (input)
  LED Page (0x08)         0x57  System Microphone Mute  OOC (output)

The input usage already maps to KEY_MICMUTE, so the button works on
HUTRR110 devices.  The LED output usage is ignored, though, so the
indicator stays dark and userspace depends on per-vendor hacks
(hid-lenovo, hid-lg-g15, hid-playstation, hid-plantronics) or platform
drivers instead.

Map LED page usage 0x57 to a new LED_MICMUTE input LED.  It shows up
as /sys/class/leds/inputN::micmute with the "audio-micmute" trigger
that snd-ctl-led registers, so the LED tracks the audio stack's
system-wide microphone mute state, like the existing "Mute" (LED page
0x09) mapping does for speaker mute.

LED_MICMUTE takes the next free input LED code (0x0b, below LED_MAX
0x0f), so nothing existing breaks.

Link: https://www.usb.org/sites/default/files/hutrr110-systemmicrophonemute.pdf
Cc: Jiri Kosina <jikos@kernel.org>
Cc: Benjamin Tissoires <bentiss@kernel.org>
Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc: linux-input@vger.kernel.org
Cc: linux-api@vger.kernel.org
Signed-off-by: Your Name <you@example.com>
---
 drivers/hid/hid-debug.c                | 2 +-
 drivers/hid/hid-input.c                | 1 +
 drivers/input/input-leds.c             | 1 +
 include/uapi/linux/input-event-codes.h | 1 +
 4 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/hid/hid-debug.c b/drivers/hid/hid-debug.c
index f44e6e708..92a950105 100644
--- a/drivers/hid/hid-debug.c
+++ b/drivers/hid/hid-debug.c
@@ -3550,7 +3550,7 @@ static const char *leds[LED_MAX + 1] = {
 	[LED_KANA] = "Kana",		[LED_SLEEP] = "Sleep",
 	[LED_SUSPEND] = "Suspend",	[LED_MUTE] = "Mute",
 	[LED_MISC] = "Misc",		[LED_MAIL] = "Mail",
-	[LED_CHARGING] = "Charging",
+	[LED_CHARGING] = "Charging",	[LED_MICMUTE] = "Mic Mute",
 };
 
 static const char *repeats[REP_MAX + 1] = {
diff --git a/drivers/hid/hid-input.c b/drivers/hid/hid-input.c
index edd6bbf83..727374dd5 100644
--- a/drivers/hid/hid-input.c
+++ b/drivers/hid/hid-input.c
@@ -990,6 +990,7 @@ static void hidinput_configure_usage(struct hid_input *hidinput, struct hid_fiel
 		case 0x27:  map_led (LED_SLEEP);    break;    /*   "Stand-By"                 */
 		case 0x4c:  map_led (LED_SUSPEND);  break;    /*   "System Suspend"           */
 		case 0x09:  map_led (LED_MUTE);     break;    /*   "Mute"                     */
+		case 0x57:  map_led (LED_MICMUTE);  break;    /*   "System Microphone Mute"   */
 		case 0x4b:  map_led (LED_MISC);     break;    /*   "Generic Indicator"        */
 		case 0x19:  map_led (LED_MAIL);     break;    /*   "Message Waiting"          */
 		case 0x4d:  map_led (LED_CHARGING); break;    /*   "External Power Connected" */
diff --git a/drivers/input/input-leds.c b/drivers/input/input-leds.c
index b08d1d08d..6522079a4 100644
--- a/drivers/input/input-leds.c
+++ b/drivers/input/input-leds.c
@@ -36,6 +36,7 @@ static const struct {
 	[LED_SLEEP]	= { "sleep" } ,
 	[LED_SUSPEND]	= { "suspend" },
 	[LED_MUTE]	= { "mute", AUDIO_TRIGGER("audio-mute") },
+	[LED_MICMUTE]	= { "micmute", AUDIO_TRIGGER("audio-micmute") },
 	[LED_MISC]	= { "misc" },
 	[LED_MAIL]	= { "mail" },
 	[LED_CHARGING]	= { "charging" },
diff --git a/include/uapi/linux/input-event-codes.h b/include/uapi/linux/input-event-codes.h
index 3528168f7..bc374821c 100644
--- a/include/uapi/linux/input-event-codes.h
+++ b/include/uapi/linux/input-event-codes.h
@@ -983,6 +983,7 @@
 #define LED_MISC		0x08
 #define LED_MAIL		0x09
 #define LED_CHARGING		0x0a
+#define LED_MICMUTE		0x0b
 #define LED_MAX			0x0f
 #define LED_CNT			(LED_MAX+1)
 
-- 
2.51.0