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Subject[PATCH 3/5] staging: vme: add functions for bridge module refcounting
Date
This patch adds functions that allow for reference counting
bridge modules. The patch introduces the functions
'vme_bridge_get()' and 'vme_bridge_put()'.

The functions are automatically called during .probe and .remove
for drivers.

This patch is based on the changes introduced by Emilio G. Cota
in the patch:

https://lkml.org/lkml/2010/10/25/492

Signed-off-by: Manohar Vanga <manohar.vanga@cern.ch>
---
drivers/staging/vme/bridges/vme_ca91cx42.c | 2 +
drivers/staging/vme/bridges/vme_tsi148.c | 2 +
drivers/staging/vme/vme.c | 54 ++++++++++++++++++++++++++-
drivers/staging/vme/vme.h | 1 -
drivers/staging/vme/vme_bridge.h | 1 +
5 files changed, 57 insertions(+), 3 deletions(-)
diff --git a/drivers/staging/vme/bridges/vme_ca91cx42.c b/drivers/staging/vme/bridges/vme_ca91cx42.c
index 0e4feac..b80cb12 100644
--- a/drivers/staging/vme/bridges/vme_ca91cx42.c
+++ b/drivers/staging/vme/bridges/vme_ca91cx42.c
@@ -1673,6 +1673,8 @@ static int ca91cx42_probe(struct pci_dev *pdev, const struct pci_device_id *id)
ca91cx42_bridge->parent = &pdev->dev;
strcpy(ca91cx42_bridge->name, driver_name);

+ ca91cx42_bridge->owner = THIS_MODULE;
+
/* Setup IRQ */
retval = ca91cx42_irq_init(ca91cx42_bridge);
if (retval != 0) {
diff --git a/drivers/staging/vme/bridges/vme_tsi148.c b/drivers/staging/vme/bridges/vme_tsi148.c
index 6c1167c..b0b434a 100644
--- a/drivers/staging/vme/bridges/vme_tsi148.c
+++ b/drivers/staging/vme/bridges/vme_tsi148.c
@@ -2312,6 +2312,8 @@ static int tsi148_probe(struct pci_dev *pdev, const struct pci_device_id *id)
tsi148_bridge->parent = &pdev->dev;
strcpy(tsi148_bridge->name, driver_name);

+ tsi148_bridge->owner = THIS_MODULE;
+
/* Setup IRQ */
retval = tsi148_irq_init(tsi148_bridge);
if (retval != 0) {
diff --git a/drivers/staging/vme/vme.c b/drivers/staging/vme/vme.c
index feb2d00..664eae0 100644
--- a/drivers/staging/vme/vme.c
+++ b/drivers/staging/vme/vme.c
@@ -52,6 +52,48 @@ static struct vme_bridge *dev_to_bridge(struct device *dev)
}

/*
+ * Increments the reference count of a VME bridge.
+ *
+ * On success, it can be assumed that the bridge won't be removed until
+ * the corresponding call to vme_put_bridge(). This along with
+ * vme_bridge_put are automatically called and VME device drivers need
+ * not worry about using this.
+ */
+int vme_bridge_get(unsigned int bus_id)
+{
+ int ret = -1;
+ struct vme_bridge *bridge;
+
+ mutex_lock(&vme_buses_lock);
+ list_for_each_entry(bridge, &vme_bus_list, bus_list) {
+ if (bridge->num == bus_id) {
+ if (!bridge->owner)
+ dev_warn(bridge->parent,
+ "bridge->owner not set\n");
+ else if (try_module_get(bridge->owner))
+ ret = 0;
+ break;
+ }
+ }
+ mutex_unlock(&vme_buses_lock);
+ return ret;
+}
+
+/*
+ * Decrements the reference count of a bridge
+ *
+ * This function decrements the reference count of the module that controls
+ * the bridge. It must come after a call to vme_get_bridge().
+ */
+void vme_bridge_put(struct vme_bridge *bridge)
+{
+ if (!bridge->owner)
+ dev_warn(bridge->parent, "bridge->owner not set\n");
+ else
+ module_put(bridge->owner);
+}
+
+/*
* Find the bridge that the resource is associated with.
*/
static struct vme_bridge *find_bridge(struct vme_resource *resource)
@@ -1496,14 +1538,20 @@ static int vme_bus_probe(struct device *dev)
{
struct vme_bridge *bridge;
struct vme_driver *driver;
- int retval = -ENODEV;
+ int retval = 0;

driver = dev_to_vme_driver(dev);
bridge = dev_to_bridge(dev);

+ if (vme_bridge_get(bridge->num))
+ return -ENXIO;
+
if (driver->probe != NULL)
retval = driver->probe(dev, bridge->num, vme_calc_slot(dev));

+ if (driver->probe && retval)
+ vme_bridge_put(bridge);
+
return retval;
}

@@ -1511,7 +1559,7 @@ static int vme_bus_remove(struct device *dev)
{
struct vme_bridge *bridge;
struct vme_driver *driver;
- int retval = -ENODEV;
+ int retval = 0;

driver = dev_to_vme_driver(dev);
bridge = dev_to_bridge(dev);
@@ -1519,6 +1567,8 @@ static int vme_bus_remove(struct device *dev)
if (driver->remove != NULL)
retval = driver->remove(dev, bridge->num, vme_calc_slot(dev));

+ vme_bridge_put(bridge);
+
return retval;
}

diff --git a/drivers/staging/vme/vme.h b/drivers/staging/vme/vme.h
index 4155d8c..eb00a5e 100644
--- a/drivers/staging/vme/vme.h
+++ b/drivers/staging/vme/vme.h
@@ -165,6 +165,5 @@ int vme_slot_get(struct device *);
int vme_register_driver(struct vme_driver *);
void vme_unregister_driver(struct vme_driver *);

-
#endif /* _VME_H_ */

diff --git a/drivers/staging/vme/vme_bridge.h b/drivers/staging/vme/vme_bridge.h
index 8959670..ef751a4 100644
--- a/drivers/staging/vme/vme_bridge.h
+++ b/drivers/staging/vme/vme_bridge.h
@@ -113,6 +113,7 @@ struct vme_bridge {
struct device *parent; /* Parent device (eg. pdev->dev for PCI) */
void *driver_priv; /* Private pointer for the bridge driver */
struct list_head bus_list; /* list of VME buses */
+ struct module *owner; /* module that owns the bridge */

struct device dev[VME_SLOTS_MAX]; /* Device registered with
* device model on VME bus
--
1.7.4.1


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