ALSA: core: Add memory copy helpers between iov_iter and iomem

Add two more helpers for copying memory between iov_iter and iomem,
which will be used by the new PCM copy ops in a few drivers.
The existing helpers became wrappers of those now.

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

Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Takashi Iwai <[e-mail]>

include/sound/pcm.h

···
 #define pcm_dbg(pcm, fmt, args...) \
 	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);
+
 struct snd_pcm_status64 {
 	snd_pcm_state_t state;		/* stream state */
 	u8 rsvd[4];

sound/core/memory.c

···
 #include <linux/io.h>
 #include <linux/uaccess.h>
 #include <sound/core.h>
+#include <sound/pcm.h>
 
 /**
  * copy_to_user_fromio - copy data from mmio-space to user-space
···
  */
 int copy_to_user_fromio(void __user *dst, const volatile void __iomem *src, size_t count)
 {
+	struct iov_iter iter;
+
+	if (import_ubuf(ITER_DEST, dst, count, &iter))
+		return -EFAULT;
+	return copy_to_iter_fromio(&iter, (const void __iomem *)src, count);
+}
+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
+ *
+ * Copies the data from mmio-space to iov_iter.
+ *
+ * Return: Zero if successful, or non-zero on failure.
+ */
+int copy_to_iter_fromio(struct iov_iter *dst, const void __iomem *src,
+			size_t count)
+{
 #if defined(__i386__) || defined(CONFIG_SPARC32)
-	return copy_to_user(dst, (const void __force*)src, count) ? -EFAULT : 0;
+	return copy_to_iter((const void __force *)src, count, dst) == count ? 0 : -EFAULT;
 #else
 	char buf[256];
 	while (count) {
···
 		if (c > sizeof(buf))
 			c = sizeof(buf);
 		memcpy_fromio(buf, (void __iomem *)src, c);
-		if (copy_to_user(dst, buf, c))
+		if (copy_to_iter(buf, c, dst) != c)
 			return -EFAULT;
 		count -= c;
-		dst += c;
 		src += c;
 	}
 	return 0;
 #endif
 }
-EXPORT_SYMBOL(copy_to_user_fromio);
+EXPORT_SYMBOL(copy_to_iter_fromio);
 
 /**
  * copy_from_user_toio - copy data from user-space to mmio-space
···
  */
 int copy_from_user_toio(volatile void __iomem *dst, const void __user *src, size_t count)
 {
+	struct iov_iter iter;
+
+	if (import_ubuf(ITER_SOURCE, (void __user *)src, count, &iter))
+		return -EFAULT;
+	return copy_from_iter_toio((void __iomem *)dst, &iter, count);
+}
+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
+ *
+ * Copies the data from iov_iter to mmio-space.
+ *
+ * Return: Zero if successful, or non-zero on failure.
+ */
+int copy_from_iter_toio(void __iomem *dst, struct iov_iter *src, size_t count)
+{
 #if defined(__i386__) || defined(CONFIG_SPARC32)
-	return copy_from_user((void __force *)dst, src, count) ? -EFAULT : 0;
+	return copy_from_iter((void __force *)dst, count, src) == count ? 0 : -EFAULT;
 #else
 	char buf[256];
 	while (count) {
 		size_t c = count;
 		if (c > sizeof(buf))
 			c = sizeof(buf);
-		if (copy_from_user(buf, src, c))
+		if (copy_from_iter(buf, c, src) != c)
 			return -EFAULT;
 		memcpy_toio(dst, buf, c);
 		count -= c;
 		dst += c;
-		src += c;
 	}
 	return 0;
 #endif
 }
-EXPORT_SYMBOL(copy_from_user_toio);
+EXPORT_SYMBOL(copy_from_iter_toio);