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Commit 513b032c authored by George Spelvin's avatar George Spelvin Committed by Greg Kroah-Hartman
Browse files

pps: Add pps_lookup_dev() function 



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: default avatarGeorge Spelvin <linux@horizon.com>
Acked-by: default avatarRodolfo Giometti <giometti@enneenne.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 6d53c3b7

drivers/pps/pps.c

+33 −0
Original line number Diff line number Diff line
@@ -352,10 +352,43 @@ 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

 */

include/linux/pps_kernel.h

+14 −3
Original line number Diff line number Diff line
@@ -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 */
@@ -81,6 +82,16 @@ 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

 */
@@ -88,10 +99,10 @@ extern struct device_attribute pps_attrs[]; 
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)