diff options
Diffstat (limited to 'drivers/base/core.c')
| -rw-r--r-- | drivers/base/core.c | 83 |
1 files changed, 83 insertions, 0 deletions
diff --git a/drivers/base/core.c b/drivers/base/core.c index 90f2dd4661f5..18e04ca1de13 100644 --- a/drivers/base/core.c +++ b/drivers/base/core.c @@ -44,6 +44,8 @@ early_param("sysfs.deprecated", sysfs_deprecated_setup); #endif /* Device links support. */ +static LIST_HEAD(wait_for_suppliers); +static DEFINE_MUTEX(wfs_lock); #ifdef CONFIG_SRCU static DEFINE_MUTEX(device_links_lock); @@ -418,6 +420,51 @@ struct device_link *device_link_add(struct device *consumer, } EXPORT_SYMBOL_GPL(device_link_add); +/** + * device_link_wait_for_supplier - Mark device as waiting for supplier + * @consumer: Consumer device + * + * Marks the consumer device as waiting for suppliers to become available. The + * consumer device will never be probed until it's unmarked as waiting for + * suppliers. The caller is responsible for adding the link to the supplier + * once the supplier device is present. + * + * This function is NOT meant to be called from the probe function of the + * consumer but rather from code that creates/adds the consumer device. + */ +static void device_link_wait_for_supplier(struct device *consumer) +{ + mutex_lock(&wfs_lock); + list_add_tail(&consumer->links.needs_suppliers, &wait_for_suppliers); + mutex_unlock(&wfs_lock); +} + +/** + * device_link_check_waiting_consumers - Try to unmark waiting consumers + * + * Loops through all consumers waiting on suppliers and tries to add all their + * supplier links. If that succeeds, the consumer device is unmarked as waiting + * for suppliers. Otherwise, they are left marked as waiting on suppliers, + * + * The add_links bus callback is expected to return 0 if it has found and added + * all the supplier links for the consumer device. It should return an error if + * it isn't able to do so. + * + * The caller of device_link_wait_for_supplier() is expected to call this once + * it's aware of potential suppliers becoming available. + */ +static void device_link_check_waiting_consumers(void) +{ + struct device *dev, *tmp; + + mutex_lock(&wfs_lock); + list_for_each_entry_safe(dev, tmp, &wait_for_suppliers, + links.needs_suppliers) + if (!dev->bus->add_links(dev)) + list_del_init(&dev->links.needs_suppliers); + mutex_unlock(&wfs_lock); +} + static void device_link_free(struct device_link *link) { while (refcount_dec_not_one(&link->rpm_active)) @@ -552,6 +599,19 @@ int device_links_check_suppliers(struct device *dev) struct device_link *link; int ret = 0; + /* + * If a device is waiting for one or more suppliers (in + * wait_for_suppliers list), it is not ready to probe yet. So just + * return -EPROBE_DEFER without having to check the links with existing + * suppliers. + */ + mutex_lock(&wfs_lock); + if (!list_empty(&dev->links.needs_suppliers)) { + mutex_unlock(&wfs_lock); + return -EPROBE_DEFER; + } + mutex_unlock(&wfs_lock); + device_links_write_lock(); list_for_each_entry(link, &dev->links.suppliers, c_node) { @@ -836,6 +896,10 @@ static void device_links_purge(struct device *dev) { struct device_link *link, *ln; + mutex_lock(&wfs_lock); + list_del(&dev->links.needs_suppliers); + mutex_unlock(&wfs_lock); + /* * Delete all of the remaining links from this device to any other * devices (either consumers or suppliers). @@ -1697,6 +1761,7 @@ void device_initialize(struct device *dev) #endif INIT_LIST_HEAD(&dev->links.consumers); INIT_LIST_HEAD(&dev->links.suppliers); + INIT_LIST_HEAD(&dev->links.needs_suppliers); dev->links.status = DL_DEV_NO_DRIVER; } EXPORT_SYMBOL_GPL(device_initialize); @@ -2132,6 +2197,24 @@ int device_add(struct device *dev) BUS_NOTIFY_ADD_DEVICE, dev); kobject_uevent(&dev->kobj, KOBJ_ADD); + + /* + * Check if any of the other devices (consumers) have been waiting for + * this device (supplier) to be added so that they can create a device + * link to it. + * + * This needs to happen after device_pm_add() because device_link_add() + * requires the supplier be registered before it's called. + * + * But this also needs to happe before bus_probe_device() to make sure + * waiting consumers can link to it before the driver is bound to the + * device and the driver sync_state callback is called for this device. + */ + device_link_check_waiting_consumers(); + + if (dev->bus && dev->bus->add_links && dev->bus->add_links(dev)) + device_link_wait_for_supplier(dev); + bus_probe_device(dev); if (parent) klist_add_tail(&dev->p->knode_parent, |