[PATCH 3/4] pps: Use lookup list to reduce ldisc coupling

Peter Hurley
2013-02-06T15:57:08Z

Now that N_TTY uses tty->disc_data for its private data,
'subclass' ldiscs cannot use ->disc_data for their own private data.

Use a lookup list to associate the tty with the pps source.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
---
drivers/pps/clients/pps-ldisc.c | 64 +++++++++++++++++++++++++++++++++++++----
1 file changed, 59 insertions(+), 5 deletions(-)

diff --git a/drivers/pps/clients/pps-ldisc.c b/drivers/pps/clients/pps-ldisc.c
index 0b91d91..a36d42b 100644
--- a/drivers/pps/clients/pps-ldisc.c
+++ b/drivers/pps/clients/pps-ldisc.c
@@ -25,17 +25,47 @@
#include <linux/serial_core.h>
#include <linux/tty.h>
#include <linux/pps_kernel.h>
+#include <linux/list.h>
+#include <linux/spinlock.h>
+#include <linux/slab.h>
#include <linux/bug.h>

#define PPS_TTY_MAGIC 0x0001

+struct pps_data {
+ struct pps_device *pps;
+ struct tty_struct *tty;
+ struct list_head link;
+};
+
+DEFINE_SPINLOCK(pps_lock);
+static LIST_HEAD(pps_list);
+
+static struct pps_device *lookup_pps_by_tty(struct tty_struct *tty,
+ struct pps_data **p)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&pps_lock, flags);
+ list_for_each_entry((*p), &pps_list, link) {
+ if ((*p)->tty == tty) {
+ spin_unlock_irqrestore(&pps_lock, flags);
+ return (*p)->pps;
+ }
+ }
+ spin_unlock_irqrestore(&pps_lock, flags);
+ return NULL;
+}
+
static void pps_tty_dcd_change(struct tty_struct *tty, unsigned int status)
{
struct pps_event_time ts;
- struct pps_device *pps = (struct pps_device *)tty->disc_data;
+ struct pps_device *pps;
+ struct pps_data *data;

pps_get_ts(&ts);

+ pps = lookup_pps_by_tty(tty, &data);
if (WARN_ON_ONCE(pps == NULL))
return;

@@ -55,6 +85,8 @@ static int pps_tty_open(struct tty_struct *tty)
struct tty_driver *drv = tty->driver;
int index = tty->index + drv->name_base;
struct pps_device *pps;
+ struct pps_data *data;
+ unsigned long flags;
int ret;

info.owner = THIS_MODULE;
@@ -71,7 +103,12 @@ static int pps_tty_open(struct tty_struct *tty)
pr_err("cannot register PPS source \"%s\"\n", info.path);
return -ENOMEM;
}
- tty->disc_data = pps;
+
+ data = kzalloc(sizeof(*data), GFP_KERNEL);
+ if (!data) {
+ ret = -ENOMEM;
+ goto err_unregister;
+ }

/* Should open N_TTY ldisc too */
ret = alias_n_tty_open(tty);
@@ -80,12 +117,19 @@ static int pps_tty_open(struct tty_struct *tty)
goto err_unregister;
}

+ data->pps = pps;
+ data->tty = tty;
+ INIT_LIST_HEAD(&data->link);
+ spin_lock_irqsave(&pps_lock, flags);
+ list_add(&data->link, &pps_list);
+ spin_unlock_irqrestore(&pps_lock, flags);
+
dev_info(pps->dev, "source \"%s\" added\n", info.path);

return 0;

err_unregister:
- tty->disc_data = NULL;
+ kfree(data);
pps_unregister_source(pps);
return ret;
}
@@ -94,13 +138,23 @@ static void (*alias_n_tty_close)(struct tty_struct *tty);

static void pps_tty_close(struct tty_struct *tty)
{
- struct pps_device *pps = (struct pps_device *)tty->disc_data;
+ struct pps_device *pps;
+ struct pps_data *data;
+ unsigned long flags;

alias_n_tty_close(tty);

- tty->disc_data = NULL;
+ pps = lookup_pps_by_tty(tty, &data);
+ if (!pps)
+ return;
+
dev_info(pps->dev, "removed\n");
pps_unregister_source(pps);
+
+ spin_lock_irqsave(&pps_lock, flags);
+ list_del(&data->link);
+ spin_unlock_irqrestore(&pps_lock, flags);
+ kfree(data);
}

static struct tty_ldisc_ops pps_ldisc_ops;
--
1.8.1.2