Add separate functions, feature_dev_{register,unregister}(), that wrap
platform_device_add() and platform_device_unregister(), respectively.
These are invoked once per feature device in this commit but will be
reused in a subsequent commit to destroy and recreate the platform
device when the corresponding port is released and reassigned.

The function feature_dev_register() will be extended in subsequent
commits to allocate the platform device, add resources and platform
data, and finally add the platform device to the device hierarchy.

Signed-off-by: Peter Colberg <peter.colberg@intel.com>
Reviewed-by: Matthew Gerlach <matthew.gerlach@linux.intel.com>
Reviewed-by: Basheer Ahmed Muddebihal <basheer.ahmed.muddebihal@linux.intel.com>
Acked-by: Xu Yilun <yilun.xu@intel.com>
---
Changes since v4:
- Move reset of device pointer in feature data to NULL in the function
  feature_dev_unregister() from this patch to the patch "allocate
  platform device after feature device data", which contains the
  corresponding initialization of the device pointer in
  feature_dev_register().

Changes since v3:
- New patch extracted from last patch of v3 series.
---
 drivers/fpga/dfl.c | 30 ++++++++++++++++++++++++++----
 1 file changed, 26 insertions(+), 4 deletions(-)

diff --git a/drivers/fpga/dfl.c b/drivers/fpga/dfl.c
index e8488a771337..e681b100524c 100644
--- a/drivers/fpga/dfl.c
+++ b/drivers/fpga/dfl.c
@@ -872,12 +872,34 @@ build_info_create_dev(struct build_feature_devs_info *binfo)
 	if (fdev->id < 0)
 		return fdev->id;
 
-	fdev->dev.parent = &binfo->cdev->region->dev;
-	fdev->dev.devt = dfl_get_devt(dfl_devs[type].devt_type, fdev->id);
+	return 0;
+}
+
+/*
+ * register current feature device, it is called when we need to switch to
+ * another feature parsing or we have parsed all features on given device
+ * feature list.
+ */
+static int feature_dev_register(struct dfl_feature_dev_data *fdata)
+{
+	struct platform_device *fdev = fdata->dev;
+	int ret;
+
+	fdev->dev.parent = &fdata->dfl_cdev->region->dev;
+	fdev->dev.devt = dfl_get_devt(dfl_devs[fdata->type].devt_type, fdev->id);
+
+	ret = platform_device_add(fdev);
+	if (ret)
+		return ret;
 
 	return 0;
 }
 
+static void feature_dev_unregister(struct dfl_feature_dev_data *fdata)
+{
+	platform_device_unregister(fdata->dev);
+}
+
 static int build_info_commit_dev(struct build_feature_devs_info *binfo)
 {
 	struct dfl_feature_dev_data *fdata;
@@ -887,7 +909,7 @@ static int build_info_commit_dev(struct build_feature_devs_info *binfo)
 	if (IS_ERR(fdata))
 		return PTR_ERR(fdata);
 
-	ret = platform_device_add(binfo->feature_dev);
+	ret = feature_dev_register(fdata);
 	if (ret)
 		return ret;
 
@@ -1519,7 +1541,7 @@ static int remove_feature_dev(struct device *dev, void *data)
 	struct platform_device *pdev = to_platform_device(dev);
 	int id = pdev->id;
 
-	platform_device_unregister(pdev);
+	feature_dev_unregister(fdata);
 
 	dfl_id_free(fdata->type, id);
 
-- 
2.47.0