Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757900Ab3CDDyo (ORCPT ); Sun, 3 Mar 2013 22:54:44 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:33068 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756919Ab3CDDo2 (ORCPT ); Sun, 3 Mar 2013 22:44:28 -0500 Message-Id: <20130304033712.861646866@decadent.org.uk> User-Agent: quilt/0.60-1 Date: Mon, 04 Mar 2013 03:38:00 +0000 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: akpm@linux-foundation.org, George Spelvin , Rodolfo Giometti , Greg Kroah-Hartman Subject: [ 053/153] pps: Add pps_lookup_dev() function In-Reply-To: <20130304033707.648729212@decadent.org.uk> X-SA-Exim-Connect-IP: 2001:470:1f08:1539:a11:96ff:fec6:70c4 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4262 Lines: 131 3.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: George Spelvin commit 513b032c98b4b9414aa4e9b4a315cb1bf0380101 upstream. The PPS serial line discipline wants to attach a PPS device to a tty without changing the tty code to add a struct pps_device * pointer. Since the number of PPS devices in a typical system is generally very low (n=1 is by far the most common), it's practical to search the entire list of allocated pps devices. (We capture the timestamp before the lookup, so the timing isn't affected.) It is a bit ugly that this function, which is part of the in-kernel PPS API, has to be in pps.c as opposed to kapi,c, but that's not something that affects users. Signed-off-by: George Spelvin Acked-by: Rodolfo Giometti Signed-off-by: Greg Kroah-Hartman Signed-off-by: Ben Hutchings --- drivers/pps/pps.c | 33 +++++++++++++++++++++++++++++++++ include/linux/pps_kernel.h | 17 ++++++++++++++--- 2 files changed, 47 insertions(+), 3 deletions(-) --- a/drivers/pps/pps.c +++ b/drivers/pps/pps.c @@ -350,11 +350,44 @@ free_idr: void pps_unregister_cdev(struct pps_device *pps) { + pps->lookup_cookie = NULL; device_destroy(pps_class, pps->dev->devt); cdev_del(&pps->cdev); } /* + * Look up a pps device by magic cookie. + * The cookie is usually a pointer to some enclosing device, but this + * code doesn't care; you should never be dereferencing it. + * + * This is a bit of a kludge that is currently used only by the PPS + * serial line discipline. It may need to be tweaked when a second user + * is found. + * + * There is no function interface for setting the lookup_cookie field. + * It's initialized to NULL when the pps device is created, and if a + * client wants to use it, just fill it in afterward. + * + * The cookie is automatically set to NULL in pps_unregister_source() + * so that it will not be used again, even if the pps device cannot + * be removed from the idr due to pending references holding the minor + * number in use. + */ +struct pps_device *pps_lookup_dev(void const *cookie) +{ + struct pps_device *pps; + unsigned id; + + rcu_read_lock(); + idr_for_each_entry(&pps_idr, pps, id) + if (cookie == pps->lookup_cookie) + break; + rcu_read_unlock(); + return pps; +} +EXPORT_SYMBOL(pps_lookup_dev); + +/* * Module stuff */ --- a/include/linux/pps_kernel.h +++ b/include/linux/pps_kernel.h @@ -43,7 +43,7 @@ struct pps_source_info { int event, void *data); /* PPS echo function */ struct module *owner; - struct device *dev; + struct device *dev; /* Parent device for device_create */ }; struct pps_event_time { @@ -69,6 +69,7 @@ struct pps_device { wait_queue_head_t queue; /* PPS event queue */ unsigned int id; /* PPS source unique ID */ + void const *lookup_cookie; /* pps_lookup_dev only */ struct cdev cdev; struct device *dev; struct fasync_struct *async_queue; /* fasync method */ @@ -82,16 +83,26 @@ struct pps_device { extern struct device_attribute pps_attrs[]; /* + * Internal functions. + * + * These are not actually part of the exported API, but this is a + * convenient header file to put them in. + */ + +extern int pps_register_cdev(struct pps_device *pps); +extern void pps_unregister_cdev(struct pps_device *pps); + +/* * Exported functions */ extern struct pps_device *pps_register_source( struct pps_source_info *info, int default_params); extern void pps_unregister_source(struct pps_device *pps); -extern int pps_register_cdev(struct pps_device *pps); -extern void pps_unregister_cdev(struct pps_device *pps); extern void pps_event(struct pps_device *pps, struct pps_event_time *ts, int event, void *data); +/* Look up a pps device by magic cookie */ +struct pps_device *pps_lookup_dev(void const *cookie); static inline void timespec_to_pps_ktime(struct pps_ktime *kt, struct timespec ts) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/