fpga: mgr: separate getting/locking FPGA manager

Previously when the user gets a FPGA manager, it was locked
and nobody else could use it for programming.

This commit makes it straightforward to save a reference to an
FPGA manager and only lock it when programming the FPGA.

Add functions that get an FPGA manager's mutex for exclusive use:
* fpga_mgr_lock
* fpga_mgr_unlock

The following functions no longer lock an FPGA manager's mutex:
* of_fpga_mgr_get
* fpga_mgr_get
* fpga_mgr_put

Signed-off-by: Alan Tull <atull@kernel.org>
Acked-by: Moritz Fischer <mdf@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 36 insertions, 16 deletions

diff --git a/drivers/fpga/fpga-mgr.c b/drivers/fpga/fpga-mgr.c
index a8dd54945470..d27e8d2a149c 100644
--- a/drivers/fpga/fpga-mgr.c
+++ b/drivers/fpga/fpga-mgr.c
@@ -410,28 +410,19 @@ ATTRIBUTE_GROUPS(fpga_mgr);
 static struct fpga_manager *__fpga_mgr_get(struct device *dev)
 {
         struct fpga_manager *mgr;
-        int ret = -ENODEV;
 
         mgr = to_fpga_manager(dev);
         if (!mgr)
                 goto err_dev;
 
-        /* Get exclusive use of fpga manager */
-        if (!mutex_trylock(&mgr->ref_mutex)) {
-                ret = -EBUSY;
-                goto err_dev;
-        }
-
         if (!try_module_get(dev->parent->driver->owner))
-                goto err_ll_mod;
+                goto err_dev;
 
         return mgr;
 
-err_ll_mod:
-        mutex_unlock(&mgr->ref_mutex);
 err_dev:
         put_device(dev);
-        return ERR_PTR(ret);
+        return ERR_PTR(-ENODEV);
 }
 
 static int fpga_mgr_dev_match(struct device *dev, const void *data)
@@ -440,10 +431,10 @@ static int fpga_mgr_dev_match(struct device *dev, const void *data)
 }
 
 /**
- * fpga_mgr_get - get an exclusive reference to a fpga mgr
+ * fpga_mgr_get - get a reference to a fpga mgr
  * @dev:        parent device that fpga mgr was registered with
  *
- * Given a device, get an exclusive reference to a fpga mgr.
+ * Given a device, get a reference to a fpga mgr.
  *
  * Return: fpga manager struct or IS_ERR() condition containing error code.
  */
@@ -464,10 +455,10 @@ static int fpga_mgr_of_node_match(struct device *dev, const void *data)
 }
 
 /**
- * of_fpga_mgr_get - get an exclusive reference to a fpga mgr
+ * of_fpga_mgr_get - get a reference to a fpga mgr
  * @node:       device node
  *
- * Given a device node, get an exclusive reference to a fpga mgr.
+ * Given a device node, get a reference to a fpga mgr.
  *
  * Return: fpga manager struct or IS_ERR() condition containing error code.
  */
@@ -491,12 +482,41 @@ EXPORT_SYMBOL_GPL(of_fpga_mgr_get);
 void fpga_mgr_put(struct fpga_manager *mgr)
 {
         module_put(mgr->dev.parent->driver->owner);
-        mutex_unlock(&mgr->ref_mutex);
         put_device(&mgr->dev);
 }
 EXPORT_SYMBOL_GPL(fpga_mgr_put);
 
 /**
+ * fpga_mgr_lock - Lock FPGA manager for exclusive use
+ * @mgr:        fpga manager
+ *
+ * Given a pointer to FPGA Manager (from fpga_mgr_get() or
+ * of_fpga_mgr_put()) attempt to get the mutex.
+ *
+ * Return: 0 for success or -EBUSY
+ */
+int fpga_mgr_lock(struct fpga_manager *mgr)
+{
+        if (!mutex_trylock(&mgr->ref_mutex)) {
+                dev_err(&mgr->dev, "FPGA manager is in use.\n");
+                return -EBUSY;
+        }
+
+        return 0;
+}
+EXPORT_SYMBOL_GPL(fpga_mgr_lock);
+
+/**
+ * fpga_mgr_unlock - Unlock FPGA manager
+ * @mgr:        fpga manager
+ */
+void fpga_mgr_unlock(struct fpga_manager *mgr)
+{
+        mutex_unlock(&mgr->ref_mutex);
+}
+EXPORT_SYMBOL_GPL(fpga_mgr_unlock);
+
+/**
  * fpga_mgr_register - register a low level fpga manager driver
  * @dev:        fpga manager device from pdev
  * @name:       fpga manager name