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    SubjectRe: [PATCH 5/8] staging: vme: add functions for bridge module refcounting
    On 01/08/11 11:20, Manohar Vanga wrote:
    > 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@cern.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;
    > + }
    > +

    Can we not do this inside vme_master_request, vme_slave_request, etc?

    I.e. Add reference count when resources are given out.

    > 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);
    > +

    This would then be done in the vme_*_free routines.

    Martyn

    > 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


    --
    Martyn Welch (Principal Software Engineer) | Registered in England and
    GE Intelligent Platforms | Wales (3828642) at 100
    T +44(0)127322748 | Barbirolli Square, Manchester,
    E martyn.welch@ge.com | M2 3AB VAT:GB 927559189


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