From 861125a75eabf6b97891d2d6acdb00b1be26419f Mon Sep 17 00:00:00 2001
From: Alan Carvalho de Assis <acassis@gmail.com>
Date: Fri, 26 Jun 2026 10:38:31 -0300
Subject: [PATCH] drivers/audio: Fix audio tone generator

The audio tone generator stopped working with the 'echo' command
since https://github.com/apache/nuttx-apps/pull/1559

Before that PR:

nsh> echo "t120o1l16b9n0baan0bn0bn0baaan0b9n0baan0b" > /dev/tone0
tone_write: Received 41 bytes
nsh>

After that PR:

nsh> echo "t120o1l16b9n0baan0bn0bn0baaan0b9n0baan0b" > /dev/tone0
tone_write: Received 40 bytes
tone_write: Received 1 bytes
nsh>

Unfortunately the Audio Tone was not block new write attempts even
when it was already playing a melody.

This commit fix it and avoids the issue caused by that PR.

Signed-off-by: Alan C. Assis <acassis@gmail.com>
---
 drivers/audio/tone.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/drivers/audio/tone.c b/drivers/audio/tone.c
index 720d9c6ee9e..df4d4bafadd 100644
--- a/drivers/audio/tone.c
+++ b/drivers/audio/tone.c
@@ -86,6 +86,7 @@ struct tone_upperhalf_s
   uint8_t channel;                     /* Output channel that drives the tone. */
   volatile bool started;               /* True: pulsed output is being generated */
   mutex_t lock;                        /* Supports mutual exclusion */
+  sem_t  busysem;                      /* Don't accept new writes if busy */
   struct pwm_info_s tone;              /* Pulsed output for Audio Tone */
   struct pwm_lowerhalf_s *devtone;
   struct oneshot_lowerhalf_s *oneshot;
@@ -665,6 +666,10 @@ tune_end:
   else
     {
       g_tune = NULL;
+
+      /* Now the user can play again */
+
+      nxsem_post(&upper->busysem);
     }
 }
 
@@ -860,6 +865,7 @@ static ssize_t tone_write(FAR struct file *filep, FAR const char *buffer,
 {
   FAR struct inode *inode = filep->f_inode;
   FAR struct tone_upperhalf_s *upper = inode->i_private;
+  int ret;
 
   /* We need to receive a string #RRGGBB = 7 bytes */
 
@@ -877,6 +883,15 @@ static ssize_t tone_write(FAR struct file *filep, FAR const char *buffer,
       return -EINVAL;
     }
 
+  /* If it is playing, then ignore new write attempts */
+
+  ret = nxsem_wait_uninterruptible(&upper->busysem);
+  if (ret < 0)
+    {
+      auderr("ERROR: Audio Tone is already playing, try again later!\n");
+      return -EAGAIN;
+    }
+
   /* Copy music to internal buffer */
 
   memcpy(tune_buf, buffer, buflen);
@@ -940,6 +955,7 @@ int tone_register(FAR const char *path, FAR struct pwm_lowerhalf_s *tone,
    */
 
   nxmutex_init(&upper->lock);
+  nxsem_init(&upper->busysem, 0, 1);
   upper->devtone = tone;
   upper->oneshot = oneshot;
   upper->channel = (uint8_t)channel;