xhci: dbgtty: use IDR to support several dbc instances.

To support systems with several xhci controllers with active
dbc on each xhci we need to use IDR to identify and give
an index to each port.

Avoid using global struct tty_driver.driver_state for storing
dbc port pointer as it won't work with several dbc ports

Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://lore.kernel.org/r/20220216095153.1303105-6-mathias.nyman@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/host/xhci-dbgcap.h

@@ -100,6 +100,7 @@ struct dbc_ep {
 struct dbc_port {
 	struct tty_port			port;
 	spinlock_t			port_lock;	/* port access */
+	int				minor;
 
 	struct list_head		read_pool;
 	struct list_head		read_queue;

drivers/usb/host/xhci-dbgtty.c

@@ -10,11 +10,14 @@
 #include <linux/slab.h>
 #include <linux/tty.h>
 #include <linux/tty_flip.h>
+#include <linux/idr.h>
 
 #include "xhci.h"
 #include "xhci-dbgcap.h"
 
 static struct tty_driver *dbc_tty_driver;
+static struct idr dbc_tty_minors;
+static DEFINE_MUTEX(dbc_tty_minors_lock);
 
 static inline struct dbc_port *dbc_to_port(struct xhci_dbc *dbc)
 {
@@ -177,7 +180,14 @@ xhci_dbc_free_requests(struct list_head *head)
 
 static int dbc_tty_install(struct tty_driver *driver, struct tty_struct *tty)
 {
-	struct dbc_port		*port = driver->driver_state;
+	struct dbc_port		*port;
+
+	mutex_lock(&dbc_tty_minors_lock);
+	port = idr_find(&dbc_tty_minors, tty->index);
+	mutex_unlock(&dbc_tty_minors_lock);
+
+	if (!port)
+		return -ENXIO;
 
 	tty->driver_data = port;
 
@@ -406,6 +416,15 @@ static int xhci_dbc_tty_register_device(struct xhci_dbc *dbc)
 
 	xhci_dbc_tty_init_port(dbc, port);
 
+	mutex_lock(&dbc_tty_minors_lock);
+	port->minor = idr_alloc(&dbc_tty_minors, port, 0, 64, GFP_KERNEL);
+	mutex_unlock(&dbc_tty_minors_lock);
+
+	if (port->minor < 0) {
+		ret = port->minor;
+		goto err_idr;
+	}
+
 	ret = kfifo_alloc(&port->write_fifo, DBC_WRITE_BUF_SIZE, GFP_KERNEL);
 	if (ret)
 		goto err_exit_port;
@@ -421,7 +440,7 @@ static int xhci_dbc_tty_register_device(struct xhci_dbc *dbc)
 		goto err_free_requests;
 
 	tty_dev = tty_port_register_device(&port->port,
-					   dbc_tty_driver, 0, NULL);
+					   dbc_tty_driver, port->minor, NULL);
 	if (IS_ERR(tty_dev)) {
 		ret = PTR_ERR(tty_dev);
 		goto err_free_requests;
@@ -437,6 +456,8 @@ err_free_requests:
 err_free_fifo:
 	kfifo_free(&port->write_fifo);
 err_exit_port:
+	idr_remove(&dbc_tty_minors, port->minor);
+err_idr:
 	xhci_dbc_tty_exit_port(port);
 
 	dev_err(dbc->dev, "can't register tty port, err %d\n", ret);
@@ -450,10 +471,14 @@ static void xhci_dbc_tty_unregister_device(struct xhci_dbc *dbc)
 
 	if (!port->registered)
 		return;
-	tty_unregister_device(dbc_tty_driver, 0);
+	tty_unregister_device(dbc_tty_driver, port->minor);
 	xhci_dbc_tty_exit_port(port);
 	port->registered = false;
 
+	mutex_lock(&dbc_tty_minors_lock);
+	idr_remove(&dbc_tty_minors, port->minor);
+	mutex_unlock(&dbc_tty_minors_lock);
+
 	kfifo_free(&port->write_fifo);
 	xhci_dbc_free_requests(&port->read_pool);
 	xhci_dbc_free_requests(&port->read_queue);
@@ -478,9 +503,8 @@ int xhci_dbc_tty_probe(struct device *dev, void __iomem *base, struct xhci_hcd *
 	if (!port)
 		return -ENOMEM;
 
-	dbc_tty_driver->driver_state = port;
-
 	dbc = xhci_alloc_dbc(dev, base, &dbc_driver);
+
 	if (!dbc) {
 		status = -ENOMEM;
 		goto out2;
@@ -514,10 +538,14 @@ int dbc_tty_init(void)
 {
 	int		ret;
 
-	dbc_tty_driver = tty_alloc_driver(1, TTY_DRIVER_REAL_RAW |
+	idr_init(&dbc_tty_minors);
+
+	dbc_tty_driver = tty_alloc_driver(64, TTY_DRIVER_REAL_RAW |
 					  TTY_DRIVER_DYNAMIC_DEV);
-	if (IS_ERR(dbc_tty_driver))
+	if (IS_ERR(dbc_tty_driver)) {
+		idr_destroy(&dbc_tty_minors);
 		return PTR_ERR(dbc_tty_driver);
+	}
 
 	dbc_tty_driver->driver_name = "dbc_serial";
 	dbc_tty_driver->name = "ttyDBC";
@@ -536,7 +564,9 @@ int dbc_tty_init(void)
 	if (ret) {
 		pr_err("Can't register dbc tty driver\n");
 		tty_driver_kref_put(dbc_tty_driver);
+		idr_destroy(&dbc_tty_minors);
 	}
+
 	return ret;
 }
 
@@ -547,4 +577,6 @@ void dbc_tty_exit(void)
 		tty_driver_kref_put(dbc_tty_driver);
 		dbc_tty_driver = NULL;
 	}
+
+	idr_destroy(&dbc_tty_minors);
 }