This is a note to let you know that I've just added the patch titled
pps: Add pps_lookup_dev() function
to my tty git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty.git
in the tty-next branch.
The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)
The patch will also be merged in the next major kernel release
during the merge window.
If you have any questions about this process, please let me know.
>From 513b032c98b4b9414aa4e9b4a315cb1bf0380101 Mon Sep 17 00:00:00 2001
From: George Spelvin <[email protected]>
Date: Sun, 10 Feb 2013 04:08:32 -0500
Subject: 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: George Spelvin <[email protected]>
Acked-by: Rodolfo Giometti <[email protected]>
Cc: stable <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
drivers/pps/pps.c | 33 +++++++++++++++++++++++++++++++++
include/linux/pps_kernel.h | 17 ++++++++++++++---
2 files changed, 47 insertions(+), 3 deletions(-)
diff --git a/drivers/pps/pps.c b/drivers/pps/pps.c
index 2420d5a..a70e384 100644
--- a/drivers/pps/pps.c
+++ b/drivers/pps/pps.c
@@ -352,11 +352,44 @@ 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
*/
diff --git a/include/linux/pps_kernel.h b/include/linux/pps_kernel.h
index 0cc45ae..7db3eb9 100644
--- 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)
--
1.8.1.rc1.5.g7e0651a
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