CAPI: Rework controller state notifier

Another step towards proper locking: Rework the callback provided to
capidrv for controller state changes. This is so far attached to an
application, which would require us to hold the corresponding lock
across notification calls.

But there is no direct relation between a controller up/down event and
an application, so let's decouple them and provide a notifier call chain
for those events instead. This notifier chain is first of all used
internally. Here we request the highest priority to unsure that
housekeeping work is done before any other notifications. The chain is
exported via [un]register_capictr_notifier to our only user, capidrv, to
replace the racy and unfixable capi20_set_callback.

Signed-off-by: Jan Kiszka <jan.kiszka@web.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 16 insertions, 6 deletions

diff --git a/drivers/isdn/capi/capidrv.c b/drivers/isdn/capi/capidrv.c
index 7d8899ad5796..bf55ed5f38e3 100644
--- a/drivers/isdn/capi/capidrv.c
+++ b/drivers/isdn/capi/capidrv.c
@@ -2210,19 +2210,24 @@ static int capidrv_delcontr(u16 contr)
 }
 
 
-static void lower_callback(unsigned int cmd, u32 contr, void *data)
+static int
+lower_callback(struct notifier_block *nb, unsigned long val, void *v)
 {
+	capi_profile profile;
+	u32 contr = (long)v;
 
-	switch (cmd) {
-	case KCI_CONTRUP:
+	switch (val) {
+	case CAPICTR_UP:
 		printk(KERN_INFO "capidrv: controller %hu up\n", contr);
-		(void) capidrv_addcontr(contr, (capi_profile *) data);
+		if (capi20_get_profile(contr, &profile) == CAPI_NOERROR)
+			(void) capidrv_addcontr(contr, &profile);
 		break;
-	case KCI_CONTRDOWN:
+	case CAPICTR_DOWN:
 		printk(KERN_INFO "capidrv: controller %hu down\n", contr);
 		(void) capidrv_delcontr(contr);
 		break;
 	}
+	return NOTIFY_OK;
 }
 
 /*
@@ -2262,6 +2267,10 @@ static void __exit proc_exit(void)
 	remove_proc_entry("capi/capidrv", NULL);
 }
 
+static struct notifier_block capictr_nb = {
+	.notifier_call = lower_callback,
+};
+
 static int __init capidrv_init(void)
 {
 	capi_profile profile;
@@ -2278,7 +2287,7 @@ static int __init capidrv_init(void)
 		return -EIO;
 	}
 
-	capi20_set_callback(&global.ap, lower_callback);
+	register_capictr_notifier(&capictr_nb);
 
 	errcode = capi20_get_profile(0, &profile);
 	if (errcode != CAPI_NOERROR) {
@@ -2300,6 +2309,7 @@ static int __init capidrv_init(void)
 
 static void __exit capidrv_exit(void)
 {
+	unregister_capictr_notifier(&capictr_nb);
 	capi20_release(&global.ap);
 
 	proc_exit();