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

An FPGA manager should not be required to provide a
write function. Move the op check to the wrapper.
Default to -EOPNOTSUP so its users will fail
gracefully.

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

drivers/fpga/fpga-mgr.c

@@ -25,6 +25,13 @@ struct fpga_mgr_devres {
 	struct fpga_manager *mgr;
 };
 
+static inline int fpga_mgr_write(struct fpga_manager *mgr, const char *buf, size_t count)
+{
+	if (mgr->mops->write)
+		return  mgr->mops->write(mgr, buf, count);
+	return -EOPNOTSUPP;
+}
+
 /*
  * After all the FPGA image has been written, do the device specific steps to
  * finish and set the FPGA into operating mode.
@@ -204,7 +211,7 @@ static int fpga_mgr_buf_load_sg(struct fpga_manager *mgr,
 
 		sg_miter_start(&miter, sgt->sgl, sgt->nents, SG_MITER_FROM_SG);
 		while (sg_miter_next(&miter)) {
-			ret = mgr->mops->write(mgr, miter.addr, miter.length);
+			ret = fpga_mgr_write(mgr, miter.addr, miter.length);
 			if (ret)
 				break;
 		}
@@ -234,7 +241,7 @@ static int fpga_mgr_buf_load_mapped(struct fpga_manager *mgr,
 	 * Write the FPGA image to the FPGA.
 	 */
 	mgr->state = FPGA_MGR_STATE_WRITE;
-	ret = mgr->mops->write(mgr, buf, count);
+	ret = fpga_mgr_write(mgr, buf, count);
 	if (ret) {
 		dev_err(&mgr->dev, "Error while writing image data to FPGA\n");
 		mgr->state = FPGA_MGR_STATE_WRITE_ERR;
@@ -578,9 +585,7 @@ struct fpga_manager *fpga_mgr_create(struct device *parent, const char *name,
 	struct fpga_manager *mgr;
 	int id, ret;
 
-	if (!mops || !mops->state ||
-	    (!mops->write && !mops->write_sg) ||
-	    (mops->write && mops->write_sg)) {
+	if (!mops || !mops->state) {
 		dev_err(parent, "Attempt to register without fpga_manager_ops\n");
 		return NULL;
 	}