[PATCH] staging: greybus: uart: convert from IDR to XArray

[Dmitry Priz <dimahtms@gmail.com>]

IDR is deprecated in favor of XArray, which manages its own
internal locking and provides a more consistent allocation API.

Convert tty_minors from an IDR to an allocating XArray. Update
the error check in gb_uart_probe() from -ENOSPC to -EBUSY, since
that is the error xa_alloc() returns when the allocation range
is exhausted, unlike idr_alloc() which returned -ENOSPC.

Build-tested and verified via boot in QEMU: the module loads,
registers with the greybus core, and unloads cleanly.

Signed-off-by: Dmitry Priz <dimahtms@gmail.com>
---
 drivers/staging/greybus/uart.c | 27 ++++++++++++++++-----------
 1 file changed, 16 insertions(+), 11 deletions(-)

diff --git a/drivers/staging/greybus/uart.c b/drivers/staging/greybus/uart.c
index 7d060b4cd33d..edd6b0e25c8c 100644
--- a/drivers/staging/greybus/uart.c
+++ b/drivers/staging/greybus/uart.c
@@ -22,7 +22,7 @@
 #include <linux/serial.h>
 #include <linux/tty_driver.h>
 #include <linux/tty_flip.h>
-#include <linux/idr.h>
+#include <linux/xarray.h>
 #include <linux/fs.h>
 #include <linux/kdev_t.h>
 #include <linux/kfifo.h>
@@ -67,7 +67,7 @@ struct gb_tty {
 };
 
 static struct tty_driver *gb_tty_driver;
-static DEFINE_IDR(tty_minors);
+static DEFINE_XARRAY_ALLOC(tty_minors);
 static DEFINE_MUTEX(table_lock);
 
 static int gb_uart_receive_data_handler(struct gb_operation *op)
@@ -342,7 +342,7 @@ static struct gb_tty *get_gb_by_minor(unsigned int minor)
 	struct gb_tty *gb_tty;
 
 	mutex_lock(&table_lock);
-	gb_tty = idr_find(&tty_minors, minor);
+	gb_tty = xa_load(&tty_minors, minor);
 	if (gb_tty) {
 		mutex_lock(&gb_tty->mutex);
 		if (gb_tty->disconnected) {
@@ -359,14 +359,19 @@ static struct gb_tty *get_gb_by_minor(unsigned int minor)
 
 static int alloc_minor(struct gb_tty *gb_tty)
 {
-	int minor;
+	u32 id;
+	int ret;
 
 	mutex_lock(&table_lock);
-	minor = idr_alloc(&tty_minors, gb_tty, 0, GB_NUM_MINORS, GFP_KERNEL);
+	ret = xa_alloc(&tty_minors, &id, gb_tty, XA_LIMIT(0, GB_NUM_MINORS - 1), GFP_KERNEL);
 	mutex_unlock(&table_lock);
-	if (minor >= 0)
-		gb_tty->minor = minor;
-	return minor;
+
+	if (ret < 0)
+		return ret;
+
+	gb_tty->minor = id;
+
+	return id;
 }
 
 static void release_minor(struct gb_tty *gb_tty)
@@ -375,7 +380,7 @@ static void release_minor(struct gb_tty *gb_tty)
 
 	gb_tty->minor = 0;	/* Maybe should use an invalid value instead */
 	mutex_lock(&table_lock);
-	idr_remove(&tty_minors, minor);
+	xa_erase(&tty_minors, minor);
 	mutex_unlock(&table_lock);
 }
 
@@ -854,7 +859,7 @@ static int gb_uart_probe(struct gbphy_device *gbphy_dev,
 
 	minor = alloc_minor(gb_tty);
 	if (minor < 0) {
-		if (minor == -ENOSPC) {
+		if (minor == -EBUSY) {
 			dev_err(&gbphy_dev->dev,
 				"no more free minor numbers\n");
 			retval = -ENODEV;
@@ -984,7 +989,7 @@ static void gb_tty_exit(void)
 {
 	tty_unregister_driver(gb_tty_driver);
 	tty_driver_kref_put(gb_tty_driver);
-	idr_destroy(&tty_minors);
+	xa_destroy(&tty_minors);
 }
 
 static const struct gbphy_device_id gb_uart_id_table[] = {
-- 
2.53.0