/********************************************************************* * * sir_dongle.c: manager for serial dongle protocol drivers * * Copyright (c) 2002 Martin Diehl * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License as * published by the Free Software Foundation; either version 2 of * the License, or (at your option) any later version. * ********************************************************************/ #include <linux/module.h> #include <linux/kernel.h> #include <linux/init.h> #include <linux/smp_lock.h> #include <linux/kmod.h> #include <net/irda/irda.h> #include "sir-dev.h" /************************************************************************** * * dongle registration and attachment * */ static LIST_HEAD(dongle_list); /* list of registered dongle drivers */ static DECLARE_MUTEX(dongle_list_lock); /* protects the list */ int irda_register_dongle(struct dongle_driver *new) { struct list_head *entry; struct dongle_driver *drv; IRDA_DEBUG(0, "%s : registering dongle \"%s\" (%d).\n", __FUNCTION__, new->driver_name, new->type); down(&dongle_list_lock); list_for_each(entry, &dongle_list) { drv = list_entry(entry, struct dongle_driver, dongle_list); if (new->type == drv->type) { up(&dongle_list_lock); return -EEXIST; } } list_add(&new->dongle_list, &dongle_list); up(&dongle_list_lock); return 0; } int irda_unregister_dongle(struct dongle_driver *drv) { down(&dongle_list_lock); list_del(&drv->dongle_list); up(&dongle_list_lock); return 0; } int sirdev_get_dongle(struct sir_dev *dev, IRDA_DONGLE type) { struct list_head *entry; const struct dongle_driver *drv = NULL; int err = -EINVAL; #ifdef CONFIG_KMOD request_module("irda-dongle-%d", type); #endif if (dev->dongle_drv != NULL) return -EBUSY; /* serialize access to the list of registered dongles */ down(&dongle_list_lock); list_for_each(entry, &dongle_list) { drv = list_entry(entry, struct dongle_driver, dongle_list); if (drv->type == type) break; else drv = NULL; } if (!drv) { err = -ENODEV; goto out_unlock; /* no such dongle */ } /* handling of SMP races with dongle module removal - three cases: * 1) dongle driver was already unregistered - then we haven't found the * requested dongle above and are already out here * 2) the module is already marked deleted but the driver is still * registered - then the try_module_get() below will fail * 3) the try_module_get() below succeeds before the module is marked * deleted - then sys_delete_module() fails and prevents the removal * because the module is in use. */ if (!try_module_get(drv->owner)) { err = -ESTALE; goto out_unlock; /* rmmod already pending */ } dev->dongle_drv = drv; if (!drv->open || (err=drv->open(dev))!=0) goto out_reject; /* failed to open driver */ up(&dongle_list_lock); return 0; out_reject: dev->dongle_drv = NULL; module_put(drv->owner); out_unlock: up(&dongle_list_lock); return err; } int sirdev_put_dongle(struct sir_dev *dev) { const struct dongle_driver *drv = dev->dongle_drv; if (drv) { if (drv->close) drv->close(dev); /* close this dongle instance */ dev->dongle_drv = NULL; /* unlink the dongle driver */ module_put(drv->owner);/* decrement driver's module refcount */ } return 0; }