linux-kernel - [PATCH] fpga manager: add notifier for manager register and unregister events

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Date:   Thu,  6 Jul 2017 18:02:57 +0200
From:   Anatolij Gustschin <agust@...x.de>
To:     Alan Tull <atull@...nel.org>
Cc:     Moritz Fischer <moritz.fischer@...us.com>,
        linux-fpga@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] fpga manager: add notifier for manager register and unregister events

Add API functions for registering and removing a notifier for FPGA
manager register/unregister events. Notify when a new FPGA manager
has been registered or when an existing manager is being removed.
This will help configuration interface drivers to get the notion
of low-level FPGA managers popping up or disappearing, when using
hotpluggable FPGA configuration devices (e.g. via USB-SPI adapters).

Signed-off-by: Anatolij Gustschin <agust@...x.de>
---
 Documentation/fpga/fpga-mgr.txt |  8 ++++++++
 drivers/fpga/fpga-mgr.c         | 34 ++++++++++++++++++++++++++++++++++
 include/linux/fpga/fpga-mgr.h   | 13 +++++++++++++
 3 files changed, 55 insertions(+)

diff --git a/Documentation/fpga/fpga-mgr.txt b/Documentation/fpga/fpga-mgr.txt
index 78f197f..e81d566 100644
--- a/Documentation/fpga/fpga-mgr.txt
+++ b/Documentation/fpga/fpga-mgr.txt
@@ -73,6 +73,14 @@ Use of these two functions is described below in "How To Support a new FPGA
 device."
 
 
+To register or unregister the notifier callback for signalling
+about the low level FPGA-Managers being added or removed:
+----------------------------------------------------------
+
+	void fpga_mgr_register_mgr_notifier(struct notifier_block *nb);
+	void fpga_mgr_unregister_mgr_notifier(struct notifier_block *nb);
+
+
 How to write an image buffer to a supported FPGA
 ================================================
 /* Include to get the API */
diff --git a/drivers/fpga/fpga-mgr.c b/drivers/fpga/fpga-mgr.c
index 188ffef..7362bb4 100644
--- a/drivers/fpga/fpga-mgr.c
+++ b/drivers/fpga/fpga-mgr.c
@@ -27,10 +27,39 @@
 #include <linux/slab.h>
 #include <linux/scatterlist.h>
 #include <linux/highmem.h>
+#include <linux/notifier.h>
 
 static DEFINE_IDA(fpga_mgr_ida);
 static struct class *fpga_mgr_class;
 
+static BLOCKING_NOTIFIER_HEAD(fpga_mgr_notifier_list);
+
+/**
+ * fpga_mgr_register_mgr_notifier() - register fpga manager notifier callback
+ * @nb: pointer to the notifier block for the callback events.
+ *
+ * Add a notifier callback for FPGA manager changes. These changes are
+ * either FPGA manager being added or removed.
+ */
+void fpga_mgr_register_mgr_notifier(struct notifier_block *nb)
+{
+	blocking_notifier_chain_register(&fpga_mgr_notifier_list, nb);
+}
+EXPORT_SYMBOL_GPL(fpga_mgr_register_mgr_notifier);
+
+/**
+ * fpga_mgr_unregister_mgr_notifier() - unregister a notifier callback
+ * @nb: pointer to the notifier block for the callback events.
+ *
+ * Remove a notifier callback. fpga_mgr_register_mgr_notifier() must have
+ * been previously called for this function to work properly.
+ */
+void fpga_mgr_unregister_mgr_notifier(struct notifier_block *nb)
+{
+	blocking_notifier_chain_unregister(&fpga_mgr_notifier_list, nb);
+}
+EXPORT_SYMBOL_GPL(fpga_mgr_unregister_mgr_notifier);
+
 /*
  * Call the low level driver's write_init function.  This will do the
  * device-specific things to get the FPGA into the state where it is ready to
@@ -518,6 +547,8 @@ int fpga_mgr_register(struct device *dev, const char *name,
 
 	dev_info(&mgr->dev, "%s registered\n", mgr->name);
 
+	blocking_notifier_call_chain(&fpga_mgr_notifier_list,
+				     FPGA_MGR_ADD, mgr);
 	return 0;
 
 error_device:
@@ -539,6 +570,9 @@ void fpga_mgr_unregister(struct device *dev)
 
 	dev_info(&mgr->dev, "%s %s\n", __func__, mgr->name);
 
+	blocking_notifier_call_chain(&fpga_mgr_notifier_list,
+				     FPGA_MGR_REMOVE, mgr);
+
 	/*
 	 * If the low level driver provides a method for putting fpga into
 	 * a desired state upon unregister, do it.
diff --git a/include/linux/fpga/fpga-mgr.h b/include/linux/fpga/fpga-mgr.h
index b4ac24c..7ed4f68 100644
--- a/include/linux/fpga/fpga-mgr.h
+++ b/include/linux/fpga/fpga-mgr.h
@@ -17,6 +17,7 @@
  */
 #include <linux/mutex.h>
 #include <linux/platform_device.h>
+#include <linux/notifier.h>
 
 #ifndef _LINUX_FPGA_MGR_H
 #define _LINUX_FPGA_MGR_H
@@ -154,4 +155,16 @@ int fpga_mgr_register(struct device *dev, const char *name,
 
 void fpga_mgr_unregister(struct device *dev);
 
+/*
+ * FPGA Manager register notifier events
+ * FPGA_MGR_ADD: a new fpga manager has been registered
+ * FPGA_MGR_REMOVE: a registered fpga manager is being removed
+ */
+#define FPGA_MGR_ADD	1
+#define FPGA_MGR_REMOVE	2
+
+void fpga_mgr_register_mgr_notifier(struct notifier_block *nb);
+
+void fpga_mgr_unregister_mgr_notifier(struct notifier_block *nb);
+
 #endif /*_LINUX_FPGA_MGR_H */
-- 
2.7.4