ALSA: usb-audio: Convert to the common vmalloc memalloc

The recent change (*) in the ALSA memalloc core allows us to drop the
special vmalloc-specific allocation and page handling.  This patch
coverts to the common code.
(*) 1fe7f397cfe2: ALSA: memalloc: Add vmalloc buffer allocation
                  support
    7e8edae39fd1: ALSA: pcm: Handle special page mapping in the
                  default mmap handler

Also, since the SG-buffer-specific PCM ops becomes identical with the
normal PCM ops, unify them again to the single ops, too.

Link: https://lore.kernel.org/r/20191105151856.10785-9-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/usb/pcm.c

@@ -785,12 +785,8 @@ static int snd_usb_hw_params(struct snd_pcm_substream *substream,
 	if (ret)
 		return ret;
 
-	if (snd_usb_use_vmalloc)
-		ret = snd_pcm_lib_alloc_vmalloc_buffer(substream,
-						       params_buffer_bytes(hw_params));
-	else
-		ret = snd_pcm_lib_malloc_pages(substream,
-					       params_buffer_bytes(hw_params));
+	ret = snd_pcm_lib_malloc_pages(substream,
+				       params_buffer_bytes(hw_params));
 	if (ret < 0)
 		goto stop_pipeline;
 
@@ -857,10 +853,7 @@ static int snd_usb_hw_free(struct snd_pcm_substream *substream)
 		snd_usb_unlock_shutdown(subs->stream->chip);
 	}
 
-	if (snd_usb_use_vmalloc)
-		return snd_pcm_lib_free_vmalloc_buffer(substream);
-	else
-		return snd_pcm_lib_free_pages(substream);
+	return snd_pcm_lib_free_pages(substream);
 }
 
 /*
@@ -1781,7 +1774,6 @@ static const struct snd_pcm_ops snd_usb_playback_ops = {
 	.prepare =	snd_usb_pcm_prepare,
 	.trigger =	snd_usb_substream_playback_trigger,
 	.pointer =	snd_usb_pcm_pointer,
-	.page =		snd_pcm_lib_get_vmalloc_page,
 };
 
 static const struct snd_pcm_ops snd_usb_capture_ops = {
@@ -1793,43 +1785,14 @@ static const struct snd_pcm_ops snd_usb_capture_ops = {
 	.prepare =	snd_usb_pcm_prepare,
 	.trigger =	snd_usb_substream_capture_trigger,
 	.pointer =	snd_usb_pcm_pointer,
-	.page =		snd_pcm_lib_get_vmalloc_page,
-};
-
-static const struct snd_pcm_ops snd_usb_playback_dev_ops = {
-	.open =		snd_usb_pcm_open,
-	.close =	snd_usb_pcm_close,
-	.ioctl =	snd_pcm_lib_ioctl,
-	.hw_params =	snd_usb_hw_params,
-	.hw_free =	snd_usb_hw_free,
-	.prepare =	snd_usb_pcm_prepare,
-	.trigger =	snd_usb_substream_playback_trigger,
-	.pointer =	snd_usb_pcm_pointer,
-	.page =		snd_pcm_sgbuf_ops_page,
-};
-
-static const struct snd_pcm_ops snd_usb_capture_dev_ops = {
-	.open =		snd_usb_pcm_open,
-	.close =	snd_usb_pcm_close,
-	.ioctl =	snd_pcm_lib_ioctl,
-	.hw_params =	snd_usb_hw_params,
-	.hw_free =	snd_usb_hw_free,
-	.prepare =	snd_usb_pcm_prepare,
-	.trigger =	snd_usb_substream_capture_trigger,
-	.pointer =	snd_usb_pcm_pointer,
-	.page =		snd_pcm_sgbuf_ops_page,
 };
 
 void snd_usb_set_pcm_ops(struct snd_pcm *pcm, int stream)
 {
 	const struct snd_pcm_ops *ops;
 
-	if (snd_usb_use_vmalloc)
-		ops = stream == SNDRV_PCM_STREAM_PLAYBACK ?
+	ops = stream == SNDRV_PCM_STREAM_PLAYBACK ?
 			&snd_usb_playback_ops : &snd_usb_capture_ops;
-	else
-		ops = stream == SNDRV_PCM_STREAM_PLAYBACK ?
-			&snd_usb_playback_dev_ops : &snd_usb_capture_dev_ops;
 	snd_pcm_set_ops(pcm, stream, ops);
 }
 
@@ -1839,7 +1802,10 @@ void snd_usb_preallocate_buffer(struct snd_usb_substream *subs)
 	struct snd_pcm_substream *s = pcm->streams[subs->direction].substream;
 	struct device *dev = subs->dev->bus->controller;
 
-	if (!snd_usb_use_vmalloc)
+	if (snd_usb_use_vmalloc)
+		snd_pcm_lib_preallocate_pages(s, SNDRV_DMA_TYPE_VMALLOC,
+					      NULL, 0, 0);
+	else
 		snd_pcm_lib_preallocate_pages(s, SNDRV_DMA_TYPE_DEV_SG,
 					      dev, 64*1024, 512*1024);
 }