ALSA: Align the syntax of iov_iter helpers with standard ones

We introduced a couple of helpers for copying iomem over iov_iter, and
the functions were formed like the former copy_from/to_user(), and the
return value was adjusted to 0/-EFAULT, which made the code transition
a bit easier at that time.

OTOH, the standard copy_from/to_iter() functions have different
argument orders and the return value, and this difference can be
confusing. It's not only confusing but dangerous; actually I did
write a wrong code due to that once :-<

For reducing the confusion, this patch changes the syntax of those
helpers to align with the standard copy_from/to_iter(). The argument
order is changed and the return value is the size of copied bytes.
The callers of those functions are updated accordingly, too.

Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Takashi Iwai <[e-mail]>

include/sound/pcm.h

···
 	dev_dbg((pcm)->card->dev, fmt, ##args)
 
 /* helpers for copying between iov_iter and iomem */
-int copy_to_iter_fromio(struct iov_iter *itert, const void __iomem *src,
-			size_t count);
-int copy_from_iter_toio(void __iomem *dst, struct iov_iter *iter, size_t count);
+size_t copy_to_iter_fromio(const void __iomem *src, size_t bytes,
+			   struct iov_iter *iter) __must_check;
+size_t copy_from_iter_toio(void __iomem *dst, size_t bytes,
+			   struct iov_iter *iter) __must_check;
 
 struct snd_pcm_status64 {
 	snd_pcm_state_t state;		/* stream state */

sound/core/memory.c

···
 
 	if (import_ubuf(ITER_DEST, dst, count, &iter))
 		return -EFAULT;
-	return copy_to_iter_fromio(&iter, (const void __iomem *)src, count);
+	if (copy_to_iter_fromio((const void __iomem *)src, count, &iter) != count)
+		return -EFAULT;
+	return 0;
 }
 EXPORT_SYMBOL(copy_to_user_fromio);
 
 /**
  * copy_to_iter_fromio - copy data from mmio-space to iov_iter
- * @dst: the destination iov_iter
  * @src: the source pointer on mmio
  * @count: the data size to copy in bytes
+ * @dst: the destination iov_iter
  *
  * Copies the data from mmio-space to iov_iter.
  *
- * Return: Zero if successful, or non-zero on failure.
+ * Return: number of bytes to be copied
  */
-int copy_to_iter_fromio(struct iov_iter *dst, const void __iomem *src,
-			size_t count)
+size_t copy_to_iter_fromio(const void __iomem *src, size_t count,
+			   struct iov_iter *dst)
 {
 #if defined(__i386__) || defined(CONFIG_SPARC32)
-	return copy_to_iter((const void __force *)src, count, dst) == count ? 0 : -EFAULT;
+	return copy_to_iter((const void __force *)src, count, dst);
 #else
 	char buf[256];
+	size_t res = 0;
+
 	while (count) {
 		size_t c = count;
 		if (c > sizeof(buf))
 			c = sizeof(buf);
 		memcpy_fromio(buf, (void __iomem *)src, c);
 		if (copy_to_iter(buf, c, dst) != c)
-			return -EFAULT;
+			return res;
 		count -= c;
 		src += c;
+		res += c;
 	}
-	return 0;
+	return res;
 #endif
 }
 EXPORT_SYMBOL(copy_to_iter_fromio);
···
 
 	if (import_ubuf(ITER_SOURCE, (void __user *)src, count, &iter))
 		return -EFAULT;
-	return copy_from_iter_toio((void __iomem *)dst, &iter, count);
+	if (copy_from_iter_toio((void __iomem *)dst, count, &iter) != count)
+		return -EFAULT;
+	return 0;
 }
 EXPORT_SYMBOL(copy_from_user_toio);
 
 /**
  * copy_from_iter_toio - copy data from iov_iter to mmio-space
  * @dst: the destination pointer on mmio-space
- * @src: the source iov_iter
  * @count: the data size to copy in bytes
+ * @src: the source iov_iter
  *
  * Copies the data from iov_iter to mmio-space.
  *
- * Return: Zero if successful, or non-zero on failure.
+ * Return: number of bytes to be copied
  */
-int copy_from_iter_toio(void __iomem *dst, struct iov_iter *src, size_t count)
+size_t copy_from_iter_toio(void __iomem *dst, size_t count,
+			   struct iov_iter *src)
 {
 #if defined(__i386__) || defined(CONFIG_SPARC32)
-	return copy_from_iter((void __force *)dst, count, src) == count ? 0 : -EFAULT;
+	return copy_from_iter((void __force *)dst, count, src);
 #else
 	char buf[256];
+	size_t res = 0;
+
 	while (count) {
 		size_t c = count;
 		if (c > sizeof(buf))
 			c = sizeof(buf);
 		if (copy_from_iter(buf, c, src) != c)
-			return -EFAULT;
+			return res;
 		memcpy_toio(dst, buf, c);
 		count -= c;
 		dst += c;
+		res += c;
 	}
-	return 0;
+	return res;
 #endif
 }
 EXPORT_SYMBOL(copy_from_iter_toio);

sound/pci/nm256/nm256.c

···
 	struct snd_pcm_runtime *runtime = substream->runtime;
 	struct nm256_stream *s = runtime->private_data;
 
-	return copy_from_iter_toio(s->bufptr + pos, src, count);
+	if (copy_from_iter_toio(s->bufptr + pos, count, src) != count)
+		return -EFAULT;
+	return 0;
 }
 
 /*
···
 	struct snd_pcm_runtime *runtime = substream->runtime;
 	struct nm256_stream *s = runtime->private_data;
 
-	return copy_to_iter_fromio(dst, s->bufptr + pos, count);
+	if (copy_to_iter_fromio(s->bufptr + pos, count, dst) != count)
+		return -EFAULT;
+	return 0;
 }
 
 #endif /* !__i386__ */

sound/pci/rme32.c

···
 {
 	struct rme32 *rme32 = snd_pcm_substream_chip(substream);
 
-	return copy_from_iter_toio(rme32->iobase + RME32_IO_DATA_BUFFER + pos,
-				   src, count);
+	if (copy_from_iter_toio(rme32->iobase + RME32_IO_DATA_BUFFER + pos,
+				count, src) != count)
+		return -EFAULT;
+	return 0;
 }
 
 /* copy callback for halfduplex mode */
···
 {
 	struct rme32 *rme32 = snd_pcm_substream_chip(substream);
 
-	return copy_to_iter_fromio(dst,
-				   rme32->iobase + RME32_IO_DATA_BUFFER + pos,
-				   count);
+	if (copy_to_iter_fromio(rme32->iobase + RME32_IO_DATA_BUFFER + pos,
+				count, dst) != count)
+		return -EFAULT;
+	return 0;
 }
 
 /*

sound/pci/rme96.c

···
 {
 	struct rme96 *rme96 = snd_pcm_substream_chip(substream);
 
-	return copy_from_iter_toio(rme96->iobase + RME96_IO_PLAY_BUFFER + pos,
-				   src, count);
+	if (copy_from_iter_toio(rme96->iobase + RME96_IO_PLAY_BUFFER + pos,
+				count, src) != count)
+		return -EFAULT;
+	return 0;
 }
 
 static int
···
 {
 	struct rme96 *rme96 = snd_pcm_substream_chip(substream);
 
-	return copy_to_iter_fromio(dst,
-				   rme96->iobase + RME96_IO_REC_BUFFER + pos,
-				   count);
+	if (copy_to_iter_fromio(rme96->iobase + RME96_IO_REC_BUFFER + pos,
+				count, dst) != count)
+		return -EFAULT;
+	return 0;
 }
 
 /*

sound/soc/qcom/lpass-platform.c

···
 
 	if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) {
 		if (is_cdc_dma_port(dai_id)) {
-			ret = copy_from_iter_toio(dma_buf, buf, bytes);
+			if (copy_from_iter_toio(dma_buf, bytes, buf) != bytes)
+				ret = -EFAULT;
 		} else {
 			if (copy_from_iter((void __force *)dma_buf, bytes, buf) != bytes)
 				ret = -EFAULT;
 		}
 	} else if (substream->stream == SNDRV_PCM_STREAM_CAPTURE) {
 		if (is_cdc_dma_port(dai_id)) {
-			ret = copy_to_iter_fromio(buf, dma_buf, bytes);
+			if (copy_to_iter_fromio(dma_buf, bytes, buf) != bytes)
+				ret = -EFAULT;
 		} else {
 			if (copy_to_iter((void __force *)dma_buf, bytes, buf) != bytes)
 				ret = -EFAULT;