ALSA: gus: Convert to generic PCM copy ops

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

Note that copy_from/to_iter() returns the copied bytes, hence the
error condition is adjusted accordingly.

Link: https://lore.kernel.org/r/20230815190136.8987-6-tiwai@suse.deSigned-off-by: Takashi Iwai <tiwai@suse.de>

sound/isa/gus/gus_pcm.c

@@ -369,7 +369,7 @@ static int playback_copy_ack(struct snd_pcm_substream *substream,
 
 static int snd_gf1_pcm_playback_copy(struct snd_pcm_substream *substream,
 				     int voice, unsigned long pos,
-				     void __user *src, unsigned long count)
+				     struct iov_iter *src, unsigned long count)
 {
 	struct snd_pcm_runtime *runtime = substream->runtime;
 	struct gus_pcm_private *pcmp = runtime->private_data;
@@ -379,27 +379,11 @@ static int snd_gf1_pcm_playback_copy(struct snd_pcm_substream *substream,
 	bpos = get_bpos(pcmp, voice, pos, len);
 	if (bpos < 0)
 		return pos;
-	if (copy_from_user(runtime->dma_area + bpos, src, len))
+	if (copy_from_iter(runtime->dma_area + bpos, len, src) != len)
 		return -EFAULT;
 	return playback_copy_ack(substream, bpos, len);
 }
 
-static int snd_gf1_pcm_playback_copy_kernel(struct snd_pcm_substream *substream,
-					    int voice, unsigned long pos,
-					    void *src, unsigned long count)
-{
-	struct snd_pcm_runtime *runtime = substream->runtime;
-	struct gus_pcm_private *pcmp = runtime->private_data;
-	unsigned int len = count;
-	int bpos;
-
-	bpos = get_bpos(pcmp, voice, pos, len);
-	if (bpos < 0)
-		return pos;
-	memcpy(runtime->dma_area + bpos, src, len);
-	return playback_copy_ack(substream, bpos, len);
-}
-
 static int snd_gf1_pcm_playback_silence(struct snd_pcm_substream *substream,
 					int voice, unsigned long pos,
 					unsigned long count)
@@ -830,8 +814,7 @@ static const struct snd_pcm_ops snd_gf1_pcm_playback_ops = {
 	.prepare =	snd_gf1_pcm_playback_prepare,
 	.trigger =	snd_gf1_pcm_playback_trigger,
 	.pointer =	snd_gf1_pcm_playback_pointer,
-	.copy_user =	snd_gf1_pcm_playback_copy,
-	.copy_kernel =	snd_gf1_pcm_playback_copy_kernel,
+	.copy =		snd_gf1_pcm_playback_copy,
 	.fill_silence =	snd_gf1_pcm_playback_silence,
 };