[RFC PATCH] fpga: fpga-bridge: Add manual set option via sysfs

[Nava kishore Manne]

This patch is intended for manual testing only.
It is provide an option to manually test bridges.

Enabling bridge (!0 values are handled)
br1# echo 1 > /sys/class/fpga_bridge/<bridge>/set

Disable bridge
br1# echo 0 > /sys/class/fpga_bridge/<bridge>/set

Signed-off-by: Nava kishore Manne <nava.kishore.manne@xxxxxxx>
---
 .../ABI/testing/sysfs-class-fpga-bridge       |  9 ++++++
 drivers/fpga/fpga-bridge.c                    | 30 +++++++++++++++++++
 2 files changed, 39 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-class-fpga-bridge b/Documentation/ABI/testing/sysfs-class-fpga-bridge
index 312ae2c579d8..e157eb737bfb 100644
--- a/Documentation/ABI/testing/sysfs-class-fpga-bridge
+++ b/Documentation/ABI/testing/sysfs-class-fpga-bridge
@@ -9,3 +9,12 @@ Date:		January 2016
 KernelVersion:	4.5
 Contact:	Alan Tull <atull@xxxxxxxxxxxxxxxxxxxxx>
 Description:	Show bridge state as "enabled" or "disabled"
+
+What:		/sys/class/fpga_bridge/<bridge>/set
+Date:		May 2023
+KernelVersion:	6.4
+Contact:	Nava kishore Manne <nava.kishore.manne@xxxxxxx>
+Description:	Manual set bridge state (0-disable, !0 enable).
+		Enabling this option requires that the module is
+		compiled with #define DEBUG which is enabled by default
+		when CONFIG_DEBUG_KERNEL is setup.
diff --git a/drivers/fpga/fpga-bridge.c b/drivers/fpga/fpga-bridge.c
index a6c25dee9cc1..54d15b709b10 100644
--- a/drivers/fpga/fpga-bridge.c
+++ b/drivers/fpga/fpga-bridge.c
@@ -13,6 +13,12 @@
 #include <linux/slab.h>
 #include <linux/spinlock.h>
 
+/* For enabling manual bridge set(enable/disable) function */
+#ifdef CONFIG_DEBUG_KERNEL
+#undef DEBUG
+#define DEBUG
+#endif
+
 static DEFINE_IDA(fpga_bridge_ida);
 static struct class *fpga_bridge_class;
 
@@ -307,9 +313,33 @@ static ssize_t state_show(struct device *dev,
 static DEVICE_ATTR_RO(name);
 static DEVICE_ATTR_RO(state);
 
+#ifdef DEBUG
+static ssize_t set_store(struct device *dev,
+			 struct device_attribute *attr,
+			 const char *buf, size_t count)
+{
+	struct fpga_bridge *bridge = to_fpga_bridge(dev);
+	long enable;
+	int ret;
+
+	ret = kstrtol(buf, 16, &enable);
+	if (ret)
+		return ret;
+
+	if (bridge->br_ops && bridge->br_ops->enable_set)
+		enable = bridge->br_ops->enable_set(bridge, !!enable);
+
+	return count;
+}
+static DEVICE_ATTR_WO(set);
+#endif
+
 static struct attribute *fpga_bridge_attrs[] = {
 	&dev_attr_name.attr,
 	&dev_attr_state.attr,
+#ifdef DEBUG
+	&dev_attr_set.attr,
+#endif
 	NULL,
 };
 ATTRIBUTE_GROUPS(fpga_bridge);
-- 
2.25.1