1 files changed, 144 insertions, 0 deletions
diff --git a/drivers/misc/cb710/sgbuf2.c b/drivers/misc/cb710/sgbuf2.c
new file mode 100644
index 0000000000..a798fad5f0
--- /dev/null
+++ b/drivers/misc/cb710/sgbuf2.c
@@ -0,0 +1,144 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *  cb710/sgbuf2.c
+ *
+ *  Copyright by Michał Mirosław, 2008-2009
+ */
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/cb710.h>
+
+static bool sg_dwiter_next(struct sg_mapping_iter *miter)
+{
+	if (sg_miter_next(miter)) {
+		miter->consumed = 0;
+		return true;
+	} else
+		return false;
+}
+
+static bool sg_dwiter_is_at_end(struct sg_mapping_iter *miter)
+{
+	return miter->length == miter->consumed && !sg_dwiter_next(miter);
+}
+
+static uint32_t sg_dwiter_read_buffer(struct sg_mapping_iter *miter)
+{
+	size_t len, left = 4;
+	uint32_t data;
+	void *addr = &data;
+
+	do {
+		len = min(miter->length - miter->consumed, left);
+		memcpy(addr, miter->addr + miter->consumed, len);
+		miter->consumed += len;
+		left -= len;
+		if (!left)
+			return data;
+		addr += len;
+	} while (sg_dwiter_next(miter));
+
+	memset(addr, 0, left);
+	return data;
+}
+
+static inline bool needs_unaligned_copy(const void *ptr)
+{
+#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
+	return false;
+#else
+	return ((uintptr_t)ptr & 3) != 0;
+#endif
+}
+
+static bool sg_dwiter_get_next_block(struct sg_mapping_iter *miter, uint32_t **ptr)
+{
+	size_t len;
+
+	if (sg_dwiter_is_at_end(miter))
+		return true;
+
+	len = miter->length - miter->consumed;
+
+	if (likely(len >= 4 && !needs_unaligned_copy(
+			miter->addr + miter->consumed))) {
+		*ptr = miter->addr + miter->consumed;
+		miter->consumed += 4;
+		return true;
+	}
+
+	return false;
+}
+
+/**
+ * cb710_sg_dwiter_read_next_block() - get next 32-bit word from sg buffer
+ * @miter: sg mapping iterator used for reading
+ *
+ * Description:
+ *   Returns 32-bit word starting at byte pointed to by @miter@
+ *   handling any alignment issues.  Bytes past the buffer's end
+ *   are not accessed (read) but are returned as zeroes.  @miter@
+ *   is advanced by 4 bytes or to the end of buffer whichever is
+ *   closer.
+ *
+ * Context:
+ *   Same requirements as in sg_miter_next().
+ *
+ * Returns:
+ *   32-bit word just read.
+ */
+uint32_t cb710_sg_dwiter_read_next_block(struct sg_mapping_iter *miter)
+{
+	uint32_t *ptr = NULL;
+
+	if (likely(sg_dwiter_get_next_block(miter, &ptr)))
+		return ptr ? *ptr : 0;
+
+	return sg_dwiter_read_buffer(miter);
+}
+EXPORT_SYMBOL_GPL(cb710_sg_dwiter_read_next_block);
+
+static void sg_dwiter_write_slow(struct sg_mapping_iter *miter, uint32_t data)
+{
+	size_t len, left = 4;
+	void *addr = &data;
+
+	do {
+		len = min(miter->length - miter->consumed, left);
+		memcpy(miter->addr, addr, len);
+		miter->consumed += len;
+		left -= len;
+		if (!left)
+			return;
+		addr += len;
+	} while (sg_dwiter_next(miter));
+}
+
+/**
+ * cb710_sg_dwiter_write_next_block() - write next 32-bit word to sg buffer
+ * @miter: sg mapping iterator used for writing
+ * @data: data to write to sg buffer
+ *
+ * Description:
+ *   Writes 32-bit word starting at byte pointed to by @miter@
+ *   handling any alignment issues.  Bytes which would be written
+ *   past the buffer's end are silently discarded. @miter@ is
+ *   advanced by 4 bytes or to the end of buffer whichever is closer.
+ *
+ * Context:
+ *   Same requirements as in sg_miter_next().
+ */
+void cb710_sg_dwiter_write_next_block(struct sg_mapping_iter *miter, uint32_t data)
+{
+	uint32_t *ptr = NULL;
+
+	if (likely(sg_dwiter_get_next_block(miter, &ptr))) {
+		if (ptr)
+			*ptr = data;
+		else
+			return;
+	} else
+		sg_dwiter_write_slow(miter, data);
+}
+EXPORT_SYMBOL_GPL(cb710_sg_dwiter_write_next_block);
+