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Message-ID: <1312194053-32310-6-git-send-email-manohar.vanga@cern.ch>
Date: Mon, 1 Aug 2011 12:20:50 +0200
From: Manohar Vanga <manohar.vanga@...n.ch>
To: <gregkh@...e.de>
CC: <martyn.welch@...com>, <cota@...ap.org>,
<devel@...verdev.osuosl.org>, <linux-kernel@...r.kernel.org>,
Manohar Vanga <manohar.vanga@...n.ch>
Subject: [PATCH 5/8] staging: vme: add functions for bridge module refcounting
This patch adds functions that allow for reference counting
bridge modules. The patch introduces the functions
'vme_bridge_get()' and 'vme_bridge_put()'.
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@...n.ch>
---
drivers/staging/vme/bridges/vme_ca91cx42.c | 2 +
drivers/staging/vme/bridges/vme_tsi148.c | 2 +
drivers/staging/vme/devices/vme_user.c | 20 +++++++++++
drivers/staging/vme/vme.c | 48 ++++++++++++++++++++++++++++
drivers/staging/vme/vme.h | 2 +
drivers/staging/vme/vme_bridge.h | 1 +
6 files changed, 75 insertions(+), 0 deletions(-)
diff --git a/drivers/staging/vme/bridges/vme_ca91cx42.c b/drivers/staging/vme/bridges/vme_ca91cx42.c
index 15a0b19..2f9c22b 100644
--- a/drivers/staging/vme/bridges/vme_ca91cx42.c
+++ b/drivers/staging/vme/bridges/vme_ca91cx42.c
@@ -1680,6 +1680,8 @@ 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 5c147d6..9db89dc 100644
--- a/drivers/staging/vme/bridges/vme_tsi148.c
+++ b/drivers/staging/vme/bridges/vme_tsi148.c
@@ -2320,6 +2320,8 @@ 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/devices/vme_user.c b/drivers/staging/vme/devices/vme_user.c
index 3cbeb2a..7ed4a5c 100644
--- a/drivers/staging/vme/devices/vme_user.c
+++ b/drivers/staging/vme/devices/vme_user.c
@@ -118,6 +118,8 @@ static struct cdev *vme_user_cdev; /* Character device */
static struct class *vme_user_sysfs_class; /* Sysfs class */
static struct device *vme_user_bridge; /* Pointer to bridge device */
+static struct vme_bridge *vme_user_bus; /* Pointer to bridge */
+
static const int type[VME_DEVS] = { MASTER_MINOR, MASTER_MINOR,
MASTER_MINOR, MASTER_MINOR,
@@ -824,10 +826,25 @@ static int __devinit vme_user_probe(struct device *dev, int cur_bus,
}
}
+ /*
+ * Increment reference count of bridge module. We don't want things
+ * to fall over in case the bridge module is removed while the vme_user
+ * driver is still loaded.
+ */
+ vme_user_bus = vme_bridge_get(cur_bus);
+ if (!vme_user_bus) {
+ printk(KERN_ERR "%s: vme_bridge_get failed\n", driver_name);
+ err = -EINVAL;
+ goto err_bridge_get;
+ }
+
return 0;
/* Ensure counter set correcty to destroy all sysfs devices */
i = VME_DEVS;
+err_bridge_get:
+ for (i = 0; i < VME_DEVS; i++)
+ device_destroy(vme_user_sysfs_class, MKDEV(VME_MAJOR, i));
err_sysfs:
while (i > 0) {
i--;
@@ -892,6 +909,9 @@ static int __devexit vme_user_remove(struct device *dev, int cur_bus,
/* Unregiser the major and minor device numbers */
unregister_chrdev_region(MKDEV(VME_MAJOR, 0), VME_DEVS);
+ /* decrement bridge module reference */
+ vme_bridge_put(vme_user_bus);
+
return 0;
}
diff --git a/drivers/staging/vme/vme.c b/drivers/staging/vme/vme.c
index 11e28ca..759ec2b 100644
--- a/drivers/staging/vme/vme.c
+++ b/drivers/staging/vme/vme.c
@@ -52,6 +52,54 @@ static struct vme_bridge *dev_to_bridge(struct device *dev)
}
/*
+ * Increments the reference count of a VME bridge.
+ *
+ * If found, a pointer to the bridge is returned and the reference count
+ * of the module that owns it is incremented.
+ *
+ * On success, it can be assumed that the bridge won't be removed until
+ * the corresponding call to vme_put_bridge().
+ *
+ * Normally drivers should call vme_get_bridge() on a successfull .probe,
+ * and vme_put_bridge() when releasing the device, e.g. in .remove.
+ */
+struct vme_bridge *vme_bridge_get(unsigned int bus_id)
+{
+ struct vme_bridge *bridge;
+ struct vme_bridge *retp = NULL;
+
+ 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))
+ retp = bridge;
+ break;
+ }
+ }
+ mutex_unlock(&vme_buses_lock);
+ return retp;
+}
+EXPORT_SYMBOL(vme_bridge_get);
+
+/*
+ * 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);
+}
+EXPORT_SYMBOL(vme_bridge_put);
+
+/*
* Find the bridge that the resource is associated with.
*/
static struct vme_bridge *find_bridge(struct vme_resource *resource)
diff --git a/drivers/staging/vme/vme.h b/drivers/staging/vme/vme.h
index 3ccb497..8fb35e2 100644
--- a/drivers/staging/vme/vme.h
+++ b/drivers/staging/vme/vme.h
@@ -167,6 +167,8 @@ int vme_slot_get(struct device *);
int vme_register_driver(struct vme_driver *);
void vme_unregister_driver(struct vme_driver *);
+struct vme_bridge *vme_bridge_get(unsigned int bus_id);
+void vme_bridge_put(struct vme_bridge *bridge);
#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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