Re: [PATCH 4/6] staging: vme: add functions for bridge module refcounting

From: Martyn Welch
Date: Wed Aug 10 2011 - 06:10:08 EST

On 10/08/11 10:33, 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()'.
>
> 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@xxxxxxx>
> ---
> 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 | 2 +
> drivers/staging/vme/vme_bridge.h | 1 +
> 5 files changed, 61 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/vme.c b/drivers/staging/vme/vme.c
> index f811d07..0504007 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)
> @@ -1525,9 +1573,13 @@ static int vme_bus_probe(struct device *dev)
> driver = dev_to_vme_driver(dev);
> bridge = dev_to_bridge(dev);
>
> + vme_bridge_get(bridge->num);
> if (driver->probe != NULL)
> retval = driver->probe(dev, bridge->num, vme_calc_slot(dev));
>
> + if (retval)
> + vme_bridge_put(bridge);
> +
> return retval;
> }
>
> @@ -1543,6 +1595,8 @@ 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 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);
>

Given that we are recounting automatically in probe and remove, under what
circumstances would we need to call them separately?

Martyn

> #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@xxxxxx | M2 3AB VAT:GB 927559189
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