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

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 <>
Acked-by: default avatarRodolfo Giometti <>
Cc: stable <>
Signed-off-by: default avatarGreg Kroah-Hartman <>
parent 6d53c3b7
......@@ -352,10 +352,43 @@ int pps_register_cdev(struct pps_device *pps)
void pps_unregister_cdev(struct pps_device *pps)
pps->lookup_cookie = NULL;
device_destroy(pps_class, pps->dev->devt);
* 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;
idr_for_each_entry(&pps_idr, pps, id)
if (cookie == pps->lookup_cookie)
return pps;
* Module stuff
......@@ -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)
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