This function will call a bus-specific prepare_remove callback. If this call is not successful, the device cannot be safely removed, or the driver cannot be safely unbound. This operation is needed to safely execute OSPM-induced unbind or rebind of ACPI memory devices e.g. echo "PNP0C80:00" > /sys/bus/acpi/drivers/acpi_memhotplug/unbind driver_unbind and device_reprobe will use the new callback before calling device_release_driver() PROBLEM: bus_remove_device and bus_remove_driver also call device_release_driver but these functions always succeed under the core device-driver model i.e. there is no possibility of failure. These functions do not call the prepare_remove callback currently. This creates an unwanted assymetry between device/driver removal and driver unbinding. Suggestions to fix welcome. Signed-off-by: Vasilis Liaskovitis <vasilis.liaskovitis@xxxxxxxxxxxxxxxx> --- drivers/base/bus.c | 36 ++++++++++++++++++++++++++++++++++++ include/linux/device.h | 2 ++ 2 files changed, 38 insertions(+), 0 deletions(-) diff --git a/drivers/base/bus.c b/drivers/base/bus.c index 181ed26..c5dad55 100644 --- a/drivers/base/bus.c +++ b/drivers/base/bus.c @@ -34,6 +34,7 @@ static struct kset *system_kset; static int __must_check bus_rescan_devices_helper(struct device *dev, void *data); +static int bus_prepare_remove_device(struct device *dev); static struct bus_type *bus_get(struct bus_type *bus) { @@ -178,11 +179,18 @@ static ssize_t driver_unbind(struct device_driver *drv, if (dev && dev->driver == drv) { if (dev->parent) /* Needed for USB */ device_lock(dev->parent); + err = bus_prepare_remove_device(dev); + if (err) { + if (dev->parent) + device_unlock(dev->parent); + goto out; + } device_release_driver(dev); if (dev->parent) device_unlock(dev->parent); err = count; } +out: put_device(dev); bus_put(bus); return err; @@ -587,6 +595,26 @@ void bus_remove_device(struct device *dev) bus_put(dev->bus); } +/** + * device_prepare_release_driver - call driver specific operations to prepare + * for manually detaching device from driver. + * @dev: device. + * + * Prepare for detaching device from driver. + * When called for a USB interface, @dev->parent lock must be held. + * This function returns 0 if preparation is successful, non-zero error value + * otherwise. + */ +static int bus_prepare_remove_device(struct device *dev) +{ + int ret = 0; + device_lock(dev); + if (dev->bus) + ret = dev->bus->prepare_remove(dev); + device_unlock(dev); + return ret; +} + static int driver_add_attrs(struct bus_type *bus, struct device_driver *drv) { int error = 0; @@ -820,9 +848,17 @@ EXPORT_SYMBOL_GPL(bus_rescan_devices); */ int device_reprobe(struct device *dev) { + int ret; + if (dev->driver) { if (dev->parent) /* Needed for USB */ device_lock(dev->parent); + ret = bus_prepare_remove_device(dev); + if (ret) { + if (dev->parent) + device_unlock(dev->parent); + return ret; + } device_release_driver(dev); if (dev->parent) device_unlock(dev->parent); diff --git a/include/linux/device.h b/include/linux/device.h index cc3aee5..8e7055b 100644 --- a/include/linux/device.h +++ b/include/linux/device.h @@ -104,6 +104,7 @@ struct bus_type { int (*suspend)(struct device *dev, pm_message_t state); int (*resume)(struct device *dev); + int (*prepare_remove) (struct device *dev); const struct dev_pm_ops *pm; @@ -853,6 +854,7 @@ extern void device_release_driver(struct device *dev); extern int __must_check device_attach(struct device *dev); extern int __must_check driver_attach(struct device_driver *drv); extern int __must_check device_reprobe(struct device *dev); +extern int device_prepare_release_driver(struct device *dev); /* * Easy functions for dynamically creating devices on the fly -- 1.7.9 -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html