[PATCH v9 1/3] fpga: fpga-mgr: support bitstream offset in image buffer

[Ivan Bornyakov <i.bornyakov@metrotek.ru>]

It is not always whole FPGA image buffer meant to be written to the
device.

Add bitstream_start and bitstream_size to the fpga_image_info struct and
adjust fpga_mgr_write() callers with respect to them.

If initial_header_size is not known beforehand, pass whole buffer to low
level driver's write_init() so it could setup info->bitstream_start and
info->bitstream_size regardless.

Signed-off-by: Ivan Bornyakov <i.bornyakov@metrotek.ru>
---
 drivers/fpga/fpga-mgr.c       | 48 +++++++++++++++++++++++++++++------
 include/linux/fpga/fpga-mgr.h |  5 ++++
 2 files changed, 45 insertions(+), 8 deletions(-)

diff --git a/drivers/fpga/fpga-mgr.c b/drivers/fpga/fpga-mgr.c
index d49a9ce34568..c64e60e23a71 100644
--- a/drivers/fpga/fpga-mgr.c
+++ b/drivers/fpga/fpga-mgr.c
@@ -139,7 +139,8 @@ EXPORT_SYMBOL_GPL(fpga_image_info_free);
  * Call the low level driver's write_init function.  This will do the
  * device-specific things to get the FPGA into the state where it is ready to
  * receive an FPGA image. The low level driver only gets to see the first
- * initial_header_size bytes in the buffer.
+ * initial_header_size bytes in the buffer, if initial_header_size is set.
+ * Otherwise, the whole buffer will be passed.
  */
 static int fpga_mgr_write_init_buf(struct fpga_manager *mgr,
 				   struct fpga_image_info *info,
@@ -148,12 +149,10 @@ static int fpga_mgr_write_init_buf(struct fpga_manager *mgr,
 	int ret;
 
 	mgr->state = FPGA_MGR_STATE_WRITE_INIT;
-	if (!mgr->mops->initial_header_size)
-		ret = fpga_mgr_write_init(mgr, info, NULL, 0);
-	else
-		ret = fpga_mgr_write_init(
-		    mgr, info, buf, min(mgr->mops->initial_header_size, count));
+	if (mgr->mops->initial_header_size)
+		count = min(mgr->mops->initial_header_size, count);
 
+	ret = fpga_mgr_write_init(mgr, info, buf, count);
 	if (ret) {
 		dev_err(&mgr->dev, "Error preparing FPGA for writing\n");
 		mgr->state = FPGA_MGR_STATE_WRITE_INIT_ERR;
@@ -235,13 +234,33 @@ static int fpga_mgr_buf_load_sg(struct fpga_manager *mgr,
 	if (mgr->mops->write_sg) {
 		ret = fpga_mgr_write_sg(mgr, sgt);
 	} else {
+		size_t offset, count, length, bitstream_size;
 		struct sg_mapping_iter miter;
 
+		offset = info->bitstream_start;
+		bitstream_size = info->bitstream_size;
+		count = 0;
+
 		sg_miter_start(&miter, sgt->sgl, sgt->nents, SG_MITER_FROM_SG);
 		while (sg_miter_next(&miter)) {
-			ret = fpga_mgr_write(mgr, miter.addr, miter.length);
-			if (ret)
+			if (offset >= miter.length) {
+				offset -= miter.length;
+				continue;
+			}
+
+			if (bitstream_size)
+				length = min(miter.length - offset,
+					     bitstream_size - count);
+			else
+				length = miter.length - offset;
+
+			count += length;
+
+			ret = fpga_mgr_write(mgr, miter.addr + offset, length);
+			if (ret || count == bitstream_size)
 				break;
+
+			offset = 0;
 		}
 		sg_miter_stop(&miter);
 	}
@@ -265,6 +284,19 @@ static int fpga_mgr_buf_load_mapped(struct fpga_manager *mgr,
 	if (ret)
 		return ret;
 
+	if (info->bitstream_start > count) {
+		dev_err(&mgr->dev,
+			"Bitstream start %zd outruns firmware image %zd\n",
+			info->bitstream_start, count);
+		return -EINVAL;
+	}
+
+	if (info->bitstream_size)
+		count = min(info->bitstream_start + info->bitstream_size, count);
+
+	buf += info->bitstream_start;
+	count -= info->bitstream_start;
+
 	/*
 	 * Write the FPGA image to the FPGA.
 	 */
diff --git a/include/linux/fpga/fpga-mgr.h b/include/linux/fpga/fpga-mgr.h
index 0f9468771bb9..32464fd10cca 100644
--- a/include/linux/fpga/fpga-mgr.h
+++ b/include/linux/fpga/fpga-mgr.h
@@ -85,6 +85,9 @@ enum fpga_mgr_states {
  * @sgt: scatter/gather table containing FPGA image
  * @buf: contiguous buffer containing FPGA image
  * @count: size of buf
+ * @bitstream_start: offset in image buffer where bitstream data starts
+ * @bitstream_size: size of bitstream.
+ *	If 0, (count - bitstream_start) will be used.
  * @region_id: id of target region
  * @dev: device that owns this
  * @overlay: Device Tree overlay
@@ -98,6 +101,8 @@ struct fpga_image_info {
 	struct sg_table *sgt;
 	const char *buf;
 	size_t count;
+	size_t bitstream_start;
+	size_t bitstream_size;
 	int region_id;
 	struct device *dev;
 #ifdef CONFIG_OF
-- 
2.25.1