fpga: fpga-mgr: wrap the write_init() op

An FPGA manager should not be required to provide a
write_init() op if there is nothing for it do.
So add a wrapper and move the op checking.
Default to success.

[mdf@kernel.org: Reworded first line]
Signed-off-by: Tom Rix <trix@redhat.com>
Signed-off-by: Moritz Fischer <mdf@kernel.org>

drivers/fpga/fpga-mgr.c

@@ -25,6 +25,15 @@ struct fpga_mgr_devres {
 	struct fpga_manager *mgr;
 };
 
+static inline int fpga_mgr_write_init(struct fpga_manager *mgr,
+				      struct fpga_image_info *info,
+				      const char *buf, size_t count)
+{
+	if (mgr->mops->write_init)
+		return  mgr->mops->write_init(mgr, info, buf, count);
+	return 0;
+}
+
 /**
  * fpga_image_info_alloc - Allocate an FPGA image info struct
  * @dev: owning device
@@ -83,9 +92,9 @@ static int fpga_mgr_write_init_buf(struct fpga_manager *mgr,
 
 	mgr->state = FPGA_MGR_STATE_WRITE_INIT;
 	if (!mgr->mops->initial_header_size)
-		ret = mgr->mops->write_init(mgr, info, NULL, 0);
+		ret = fpga_mgr_write_init(mgr, info, NULL, 0);
 	else
-		ret = mgr->mops->write_init(
+		ret = fpga_mgr_write_init(
 		    mgr, info, buf, min(mgr->mops->initial_header_size, count));
 
 	if (ret) {
@@ -569,7 +578,7 @@ struct fpga_manager *fpga_mgr_create(struct device *parent, const char *name,
 	int id, ret;
 
 	if (!mops || !mops->write_complete || !mops->state ||
-	    !mops->write_init || (!mops->write && !mops->write_sg) ||
+	    (!mops->write && !mops->write_sg) ||
 	    (mops->write && mops->write_sg)) {
 		dev_err(parent, "Attempt to register without fpga_manager_ops\n");
 		return NULL;