ASoC: Name iov_iter argument as iterator instead of buffer

While transitioning ASoC code for iov_iter usages, I kept the argument
name as "buf" as the original code. But, iov_iter is an iterator, and
using the name "buf" may be misleading: the crucial difference is that
iov_iter can be proceeded after the operation, hence it can't be
passed twice, while a simple "buffer" sounds as if reusable.

To make the usage clearer, rename the argument from "buf" to "iter".
There is no functional changes, just names.

Fixes: 66201cacc33d ("ASoC: component: Add generic PCM copy ops")
Suggested-by: Linus Torvalds <[e-mail]>
Link: https://lore.kernel.org/r/CAHk-=wje+VkXjjfVTmK-uJdG_M5=[e-mail]
Reviewed-by: Mark Brown <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Takashi Iwai <[e-mail]>

include/sound/soc-component.h

···
 		struct snd_pcm_audio_tstamp_report *audio_tstamp_report);
 	int (*copy)(struct snd_soc_component *component,
 		    struct snd_pcm_substream *substream, int channel,
-		    unsigned long pos, struct iov_iter *buf,
+		    unsigned long pos, struct iov_iter *iter,
 		    unsigned long bytes);
 	struct page *(*page)(struct snd_soc_component *component,
 			     struct snd_pcm_substream *substream,
···
 int snd_soc_pcm_component_sync_stop(struct snd_pcm_substream *substream);
 int snd_soc_pcm_component_copy(struct snd_pcm_substream *substream,
 			       int channel, unsigned long pos,
-			       struct iov_iter *buf, unsigned long bytes);
+			       struct iov_iter *iter, unsigned long bytes);
 struct page *snd_soc_pcm_component_page(struct snd_pcm_substream *substream,
 					unsigned long offset);
 int snd_soc_pcm_component_mmap(struct snd_pcm_substream *substream,

sound/soc/soc-component.c

···
 
 int snd_soc_pcm_component_copy(struct snd_pcm_substream *substream,
 			       int channel, unsigned long pos,
-			       struct iov_iter *buf, unsigned long bytes)
+			       struct iov_iter *iter, unsigned long bytes)
 {
 	struct snd_soc_pcm_runtime *rtd = asoc_substream_to_rtd(substream);
 	struct snd_soc_component *component;
···
 		if (component->driver->copy)
 			return soc_component_ret(component,
 				component->driver->copy(component, substream,
-					channel, pos, buf, bytes));
+					channel, pos, iter, bytes));
 
 	return -EINVAL;
 }

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

···
 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 iov_iter *iter, unsigned long bytes)
 {
 	struct snd_pcm_runtime *runtime = substream->runtime;
 	struct dmaengine_pcm *pcm = soc_component_to_pcm(component);
···
 			channel * (runtime->dma_bytes / runtime->channels);
 
 	if (is_playback)
-		if (copy_from_iter(dma_ptr, bytes, buf) != bytes)
+		if (copy_from_iter(dma_ptr, bytes, iter) != bytes)
 			return -EFAULT;
 
 	if (process) {
···
 	}
 
 	if (!is_playback)
-		if (copy_to_iter(dma_ptr, bytes, buf) != bytes)
+		if (copy_to_iter(dma_ptr, bytes, iter) != bytes)
 			return -EFAULT;
 
 	return 0;