ALSA: core: pass audio tstamp config from userspace

Let userspace select audio timestamp config when the
STATUS_EXT ioctl is used, ignore and zero all
other fields
No change for the existing STATUS ioctl, parameters
are treated as read-only.
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/core/pcm_native.c

@@ -753,12 +753,21 @@ int snd_pcm_status(struct snd_pcm_substream *substream,
 }
 
 static int snd_pcm_status_user(struct snd_pcm_substream *substream,
-			       struct snd_pcm_status __user * _status)
+			       struct snd_pcm_status __user * _status,
+			       bool ext)
 {
 	struct snd_pcm_status status;
 	int res;
-	
+
 	memset(&status, 0, sizeof(status));
+	/*
+	 * with extension, parameters are read/write,
+	 * get audio_tstamp_data from user,
+	 * ignore rest of status structure
+	 */
+	if (ext && get_user(status.audio_tstamp_data,
+				(u32 __user *)(&_status->audio_tstamp_data)))
+		return -EFAULT;
 	res = snd_pcm_status(substream, &status);
 	if (res < 0)
 		return res;
@@ -2723,7 +2732,9 @@ static int snd_pcm_common_ioctl1(struct file *file,
 	case SNDRV_PCM_IOCTL_SW_PARAMS:
 		return snd_pcm_sw_params_user(substream, arg);
 	case SNDRV_PCM_IOCTL_STATUS:
-		return snd_pcm_status_user(substream, arg);
+		return snd_pcm_status_user(substream, arg, false);
+	case SNDRV_PCM_IOCTL_STATUS_EXT:
+		return snd_pcm_status_user(substream, arg, true);
 	case SNDRV_PCM_IOCTL_CHANNEL_INFO:
 		return snd_pcm_channel_info_user(substream, arg);
 	case SNDRV_PCM_IOCTL_PREPARE: