From: Pavel Pisa <pisa@cmp.felk.cvut.cz>
Date: Mon, 29 Jul 2019 17:21:50 +0000 (+0200)
Subject: sllin: register the second line discipline to distinguish request for slave configura... 
X-Git-Url: http://rtime.felk.cvut.cz/gitweb/linux-lin.git/commitdiff_plain/b56f1ea7a09bf50fc5f115a0c2e148e17d9e4799

sllin: register the second line discipline to distinguish request for slave configuration.

This allows to combining master and slave devices on single
computer/system.

Signed-off-by: Pavel Pisa <pisa@cmp.felk.cvut.cz>
---

diff --git a/sllin/sllin.c b/sllin/sllin.c
index ff9b0fe..cdc4327 100644
--- a/sllin/sllin.c
+++ b/sllin/sllin.c
@@ -72,6 +72,7 @@
 
 /* Should be in include/linux/tty.h */
 #define N_SLLIN			25
+#define N_SLLIN_SLAVE		26
 /* -------------------------------- */
 
 #ifdef SLLIN_LED_TRIGGER
@@ -1597,7 +1598,7 @@ static struct sllin *sll_alloc(dev_t line)
  * Called in process context serialized from other ldisc calls.
  */
 
-static int sllin_open(struct tty_struct *tty)
+static int sllin_open_common(struct tty_struct *tty, bool setup_master)
 {
 	struct sllin *sl;
 	int err;
@@ -1638,8 +1639,8 @@ static int sllin_open(struct tty_struct *tty)
 
 	if (!test_bit(SLF_INUSE, &sl->flags)) {
 		/* Perform the low-level SLLIN initialization. */
-		sl->lin_master = master;
-		if (master)
+		sl->lin_master = setup_master;
+		if (sl->lin_master)
 			pr_debug("sllin: Configured as MASTER\n");
 		else
 			pr_debug("sllin: Configured as SLAVE\n");
@@ -1704,6 +1705,43 @@ err_exit:
 	return err;
 }
 
+/*
+ * Open the high-level part of the SLLIN channel.
+ * This function is called by the TTY module when the
+ * SLLIN line discipline is called for.  Because we are
+ * sure the tty line exists, we only have to link it to
+ * a free SLLIN channel...
+ *
+ * Called in process context serialized from other ldisc calls.
+ *
+ * This call variant preserves original functionality where
+ * slave/master can be selected by module parameter.
+ * Default is the master.
+ */
+
+static int sllin_open(struct tty_struct *tty)
+{
+	return sllin_open_common(tty, master);
+}
+
+/*
+ * Open the high-level part of the SLLIN channel.
+ * This function is called by the TTY module when the
+ * SLLIN line discipline is called for.  Because we are
+ * sure the tty line exists, we only have to link it to
+ * a free SLLIN channel...
+ *
+ * Called in process context serialized from other ldisc calls.
+ *
+ * This call variant enforces slave/LIN device functionality.
+ */
+
+static int sllin_open_slave(struct tty_struct *tty)
+{
+	return sllin_open_common(tty, false);
+}
+
+
 /*
  * Close down a SLLIN channel.
  * This means flushing out any pending queues, and then returning. This
@@ -1775,6 +1813,18 @@ static struct tty_ldisc_ops sll_ldisc = {
 	.write_wakeup	= sllin_write_wakeup,
 };
 
+static struct tty_ldisc_ops sll_slave_ldisc = {
+	.owner		= THIS_MODULE,
+	.magic		= TTY_LDISC_MAGIC,
+	.name		= "sllin-slave",
+	.open		= sllin_open_slave,
+	.close		= sllin_close,
+	.hangup		= sllin_hangup,
+	.ioctl		= sllin_ioctl,
+	.receive_buf	= sllin_receive_buf,
+	.write_wakeup	= sllin_write_wakeup,
+};
+
 static int __init sllin_init(void)
 {
 	int status;
@@ -1802,8 +1852,16 @@ static int __init sllin_init(void)
 	if (status)  {
 		pr_err("sllin: can't register line discipline\n");
 		kfree(sllin_devs);
+	} else {
+		status = tty_register_ldisc(N_SLLIN_SLAVE, &sll_slave_ldisc);
+		if (status)  {
+			tty_unregister_ldisc(N_SLLIN);
+			pr_err("sllin: can't register slave line discipline\n");
+			kfree(sllin_devs);
+		}
 	}
 
+
 	if (break_by_baud)
 		pr_debug("sllin: Break is generated by baud-rate change.");
 	else
@@ -1874,6 +1932,11 @@ static void __exit sllin_exit(void)
 	if (i)
 		pr_err("sllin: can't unregister ldisc (err %d)\n", i);
 
+	i = tty_unregister_ldisc(N_SLLIN_SLAVE);
+	if (i)
+		pr_err("sllin: can't unregister slave ldisc (err %d)\n", i);
+
+
 #ifdef SLLIN_LED_TRIGGER
 	unregister_netdevice_notifier(&sllin_netdev_notifier);
 #endif