ALSA: pcm: Allow NULL ioctl ops

Currently PCM ioctl ops is a mandatory field but almost all drivers
simply pass snd_pcm_lib_ioctl.  For simplicity, allow to set NULL in
the field and call snd_pcm_lib_ioctl() as default.

Link: https://lore.kernel.org/r/20191117085308.23915-4-tiwai@suse.deSigned-off-by: Takashi Iwai <tiwai@suse.de>

sound/core/pcm_native.c

@@ -178,6 +178,16 @@ void snd_pcm_stream_unlock_irqrestore(struct snd_pcm_substream *substream,
 }
 EXPORT_SYMBOL_GPL(snd_pcm_stream_unlock_irqrestore);
 
+/* Run PCM ioctl ops */
+static int snd_pcm_ops_ioctl(struct snd_pcm_substream *substream,
+			     unsigned cmd, void *arg)
+{
+	if (substream->ops->ioctl)
+		return substream->ops->ioctl(substream, cmd, arg);
+	else
+		return snd_pcm_lib_ioctl(substream, cmd, arg);
+}
+
 int snd_pcm_info(struct snd_pcm_substream *substream, struct snd_pcm_info *info)
 {
 	struct snd_pcm *pcm = substream->pcm;
@@ -448,8 +458,9 @@ static int fixup_unreferenced_params(struct snd_pcm_substream *substream,
 		m = hw_param_mask_c(params, SNDRV_PCM_HW_PARAM_FORMAT);
 		i = hw_param_interval_c(params, SNDRV_PCM_HW_PARAM_CHANNELS);
 		if (snd_mask_single(m) && snd_interval_single(i)) {
-			err = substream->ops->ioctl(substream,
-					SNDRV_PCM_IOCTL1_FIFO_SIZE, params);
+			err = snd_pcm_ops_ioctl(substream,
+						SNDRV_PCM_IOCTL1_FIFO_SIZE,
+						params);
 			if (err < 0)
 				return err;
 		}
@@ -971,7 +982,7 @@ static int snd_pcm_channel_info(struct snd_pcm_substream *substream,
 		return -EINVAL;
 	memset(info, 0, sizeof(*info));
 	info->channel = channel;
-	return substream->ops->ioctl(substream, SNDRV_PCM_IOCTL1_CHANNEL_INFO, info);
+	return snd_pcm_ops_ioctl(substream, SNDRV_PCM_IOCTL1_CHANNEL_INFO, info);
 }
 
 static int snd_pcm_channel_info_user(struct snd_pcm_substream *substream,
@@ -1647,7 +1658,7 @@ static int snd_pcm_pre_reset(struct snd_pcm_substream *substream, int state)
 static int snd_pcm_do_reset(struct snd_pcm_substream *substream, int state)
 {
 	struct snd_pcm_runtime *runtime = substream->runtime;
-	int err = substream->ops->ioctl(substream, SNDRV_PCM_IOCTL1_RESET, NULL);
+	int err = snd_pcm_ops_ioctl(substream, SNDRV_PCM_IOCTL1_RESET, NULL);
 	if (err < 0)
 		return err;
 	runtime->hw_ptr_base = 0;