[PATCH v3 1/3] fpga: dfl: add the match() ops for dfl driver

[Xu Yilun <yilun.xu@xxxxxxxxx>]

The match ops allows dfl drivers have their own matching algorithem
instead of the standard id_table matching.

This is to support the DFL UIO driver. It intends to match any DFL
device which could not be handled by other DFL drivers.

Signed-off-by: Xu Yilun <yilun.xu@xxxxxxxxx>
---
v3: this patch is splited out from DFL UIO patch.
    move the declarations of exported symbols from include/linux/dfl.h
     to driver/fpga/dfl.h
    fix some comments.
---
 drivers/fpga/dfl.c  | 22 +++++++++++++++++-----
 drivers/fpga/dfl.h  |  5 +++++
 include/linux/dfl.h |  3 +++
 3 files changed, 25 insertions(+), 5 deletions(-)

diff --git a/drivers/fpga/dfl.c b/drivers/fpga/dfl.c
index 511b20f..dd90111 100644
--- a/drivers/fpga/dfl.c
+++ b/drivers/fpga/dfl.c
@@ -256,12 +256,13 @@ dfl_match_one_device(const struct dfl_device_id *id, struct dfl_device *ddev)
 	return NULL;
 }
 
-static int dfl_bus_match(struct device *dev, struct device_driver *drv)
+int dfl_match_device(struct dfl_device *ddev, struct dfl_driver *ddrv)
 {
-	struct dfl_device *ddev = to_dfl_dev(dev);
-	struct dfl_driver *ddrv = to_dfl_drv(drv);
 	const struct dfl_device_id *id_entry;
 
+	if (ddrv->match)
+		return ddrv->match(ddev);
+
 	id_entry = ddrv->id_table;
 	if (id_entry) {
 		while (id_entry->feature_id) {
@@ -275,6 +276,15 @@ static int dfl_bus_match(struct device *dev, struct device_driver *drv)
 
 	return 0;
 }
+EXPORT_SYMBOL_GPL(dfl_match_device);
+
+static int dfl_bus_match(struct device *dev, struct device_driver *drv)
+{
+	struct dfl_device *ddev = to_dfl_dev(dev);
+	struct dfl_driver *ddrv = to_dfl_drv(drv);
+
+	return dfl_match_device(ddev, ddrv);
+}
 
 static int dfl_bus_probe(struct device *dev)
 {
@@ -328,7 +338,7 @@ static struct attribute *dfl_dev_attrs[] = {
 };
 ATTRIBUTE_GROUPS(dfl_dev);
 
-static struct bus_type dfl_bus_type = {
+struct bus_type dfl_bus_type = {
 	.name		= "dfl",
 	.match		= dfl_bus_match,
 	.probe		= dfl_bus_probe,
@@ -336,6 +346,7 @@ static struct bus_type dfl_bus_type = {
 	.uevent		= dfl_bus_uevent,
 	.dev_groups	= dfl_dev_groups,
 };
+EXPORT_SYMBOL_GPL(dfl_bus_type);
 
 static void release_dfl_dev(struct device *dev)
 {
@@ -469,7 +480,8 @@ static int dfl_devs_add(struct dfl_feature_platform_data *pdata)
 
 int __dfl_driver_register(struct dfl_driver *dfl_drv, struct module *owner)
 {
-	if (!dfl_drv || !dfl_drv->probe || !dfl_drv->id_table)
+	if (!dfl_drv || !dfl_drv->probe ||
+	    (!dfl_drv->id_table && !dfl_drv->match))
 		return -EINVAL;
 
 	dfl_drv->drv.owner = owner;
diff --git a/drivers/fpga/dfl.h b/drivers/fpga/dfl.h
index 2b82c96..01c43d8 100644
--- a/drivers/fpga/dfl.h
+++ b/drivers/fpga/dfl.h
@@ -17,6 +17,7 @@
 #include <linux/bitfield.h>
 #include <linux/cdev.h>
 #include <linux/delay.h>
+#include <linux/dfl.h>
 #include <linux/eventfd.h>
 #include <linux/fs.h>
 #include <linux/interrupt.h>
@@ -517,4 +518,8 @@ long dfl_feature_ioctl_set_irq(struct platform_device *pdev,
 			       struct dfl_feature *feature,
 			       unsigned long arg);
 
+extern struct bus_type dfl_bus_type;
+
+int dfl_match_device(struct dfl_device *ddev, struct dfl_driver *ddrv);
+
 #endif /* __FPGA_DFL_H */
diff --git a/include/linux/dfl.h b/include/linux/dfl.h
index 6cc1098..cfd98a4 100644
--- a/include/linux/dfl.h
+++ b/include/linux/dfl.h
@@ -51,6 +51,8 @@ struct dfl_device {
  * @drv: driver model structure.
  * @id_table: pointer to table of device IDs the driver is interested in.
  *	      { } member terminated.
+ * @match: returns one if given device can be handled by the driver and zero
+ *	   otherwise. If NULL, matching is based on id_table.
  * @probe: mandatory callback for device binding.
  * @remove: callback for device unbinding.
  */
@@ -58,6 +60,7 @@ struct dfl_driver {
 	struct device_driver drv;
 	const struct dfl_device_id *id_table;
 
+	int (*match)(struct dfl_device *dfl_dev);
 	int (*probe)(struct dfl_device *dfl_dev);
 	void (*remove)(struct dfl_device *dfl_dev);
 };
-- 
2.7.4