ASoC: dmaengine: Convert to generic PCM copy ops

This patch converts the ASoC dmaenging driver code to use the new
unified PCM copy callback.  It's a straightforward conversion from
*_user() to *_iter() variants.

The process callback is still using the direct pointer as of now, but
it'll be converted in the next patch.

Note that copy_from/to_iter() returns the copied bytes, hence the
error condition is adjusted accordingly.
Reviewed-by: Mark Brown <broonie@kernel.org>
Cc: Lars-Peter Clausen <lars@metafoo.de>
Link: https://lore.kernel.org/r/20230815190136.8987-22-tiwai@suse.deSigned-off-by: Takashi Iwai <tiwai@suse.de>

sound/soc/soc-generic-dmaengine-pcm.c

@@ -287,10 +287,10 @@ static snd_pcm_uframes_t dmaengine_pcm_pointer(
 		return snd_dmaengine_pcm_pointer(substream);
 }
 
-static int dmaengine_copy_user(struct snd_soc_component *component,
-			       struct snd_pcm_substream *substream,
-			       int channel, unsigned long hwoff,
-			       void __user *buf, unsigned long bytes)
+static int dmaengine_copy(struct snd_soc_component *component,
+			  struct snd_pcm_substream *substream,
+			  int channel, unsigned long hwoff,
+			  struct iov_iter *buf, unsigned long bytes)
 {
 	struct snd_pcm_runtime *runtime = substream->runtime;
 	struct dmaengine_pcm *pcm = soc_component_to_pcm(component);
@@ -300,19 +300,20 @@ static int dmaengine_copy_user(struct snd_soc_component *component,
 	bool is_playback = substream->stream == SNDRV_PCM_STREAM_PLAYBACK;
 	void *dma_ptr = runtime->dma_area + hwoff +
 			channel * (runtime->dma_bytes / runtime->channels);
+	void *ptr = (void __force *)iter_iov_addr(buf);
 
 	if (is_playback)
-		if (copy_from_user(dma_ptr, buf, bytes))
+		if (copy_from_iter(dma_ptr, bytes, buf) != bytes)
 			return -EFAULT;
 
 	if (process) {
-		int ret = process(substream, channel, hwoff, (__force void *)buf, bytes);
+		int ret = process(substream, channel, hwoff, ptr, bytes);
 		if (ret < 0)
 			return ret;
 	}
 
 	if (!is_playback)
-		if (copy_to_user(buf, dma_ptr, bytes))
+		if (copy_to_iter(dma_ptr, bytes, buf) != bytes)
 			return -EFAULT;
 
 	return 0;
@@ -337,7 +338,7 @@ static const struct snd_soc_component_driver dmaengine_pcm_component_process = {
 	.hw_params	= dmaengine_pcm_hw_params,
 	.trigger	= dmaengine_pcm_trigger,
 	.pointer	= dmaengine_pcm_pointer,
-	.copy_user	= dmaengine_copy_user,
+	.copy		= dmaengine_copy,
 	.pcm_construct	= dmaengine_pcm_new,
 };