greybus: kernel_ver: add sg copy operations for kernel < 3.11

For older kernel, < 3.11, no copy to/from buffer with skip support was
defined. This could break builds for this versions of kernel.
Add them here.

Signed-off-by: Rui Miguel Silva <rui.silva@linaro.org>
Tested-by: Mark Greer <mgreer@animalcreek.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

1 files changed, 100 insertions, 0 deletions

diff --git a/drivers/staging/greybus/kernel_ver.h b/drivers/staging/greybus/kernel_ver.h
index f95f302b2b2d..4fb949ba9b51 100644
--- a/drivers/staging/greybus/kernel_ver.h
+++ b/drivers/staging/greybus/kernel_ver.h
@@ -135,4 +135,104 @@ static inline void sysfs_remove_groups(struct kobject *kobj,
 #if LINUX_VERSION_CODE >= KERNEL_VERSION(3, 17, 0)
 #define MMC_POWER_UNDEFINED_SUPPORTED
 #endif
+
+#if LINUX_VERSION_CODE < KERNEL_VERSION(3, 11, 0)
+#include <linux/scatterlist.h>
+static inline bool sg_miter_get_next_page(struct sg_mapping_iter *miter)
+{
+	if (!miter->__remaining) {
+		struct scatterlist *sg;
+		unsigned long pgoffset;
+
+		if (!__sg_page_iter_next(&miter->piter))
+			return false;
+
+		sg = miter->piter.sg;
+		pgoffset = miter->piter.sg_pgoffset;
+
+		miter->__offset = pgoffset ? 0 : sg->offset;
+		miter->__remaining = sg->offset + sg->length -
+				(pgoffset << PAGE_SHIFT) - miter->__offset;
+		miter->__remaining = min_t(unsigned long, miter->__remaining,
+					   PAGE_SIZE - miter->__offset);
+	}
+
+	return true;
+}
+
+static inline bool sg_miter_skip(struct sg_mapping_iter *miter, off_t offset)
+{
+	sg_miter_stop(miter);
+
+	while (offset) {
+		off_t consumed;
+
+		if (!sg_miter_get_next_page(miter))
+			return false;
+
+		consumed = min_t(off_t, offset, miter->__remaining);
+		miter->__offset += consumed;
+		miter->__remaining -= consumed;
+		offset -= consumed;
+	}
+
+	return true;
+}
+
+static inline size_t _sg_copy_buffer(struct scatterlist *sgl,
+				     unsigned int nents, void *buf,
+				     size_t buflen, off_t skip,
+				     bool to_buffer)
+{
+	unsigned int offset = 0;
+	struct sg_mapping_iter miter;
+	unsigned long flags;
+	unsigned int sg_flags = SG_MITER_ATOMIC;
+
+	if (to_buffer)
+		sg_flags |= SG_MITER_FROM_SG;
+	else
+		sg_flags |= SG_MITER_TO_SG;
+
+	sg_miter_start(&miter, sgl, nents, sg_flags);
+
+	if (!sg_miter_skip(&miter, skip))
+		return false;
+
+	local_irq_save(flags);
+
+	while (sg_miter_next(&miter) && offset < buflen) {
+		unsigned int len;
+
+		len = min(miter.length, buflen - offset);
+
+		if (to_buffer)
+			memcpy(buf + offset, miter.addr, len);
+		else
+			memcpy(miter.addr, buf + offset, len);
+
+		offset += len;
+	}
+
+	sg_miter_stop(&miter);
+
+	local_irq_restore(flags);
+	return offset;
+}
+
+static inline size_t sg_pcopy_to_buffer(struct scatterlist *sgl,
+					unsigned int nents, void *buf,
+					size_t buflen, off_t skip)
+{
+	return _sg_copy_buffer(sgl, nents, buf, buflen, skip, true);
+}
+
+static inline size_t sg_pcopy_from_buffer(struct scatterlist *sgl,
+					  unsigned int nents, void *buf,
+					  size_t buflen, off_t skip)
+{
+	return _sg_copy_buffer(sgl, nents, buf, buflen, skip, false);
+}
+#endif
+
 #endif	/* __GREYBUS_KERNEL_VER_H */