Allocate minor numbers sensibly

1 files changed, 22 insertions, 5 deletions

diff --git a/char.c b/char.c
index 90bd16c..cdf4029 100644
--- a/char.c
+++ b/char.c
@@ -121,6 +121,23 @@ struct file_operations doomdev_fops = {
 
 struct class *doom_class;
 
+int alloc_minor(void) {
+	int i;
+
+	for (i = 0; i < DOOMDEV_COUNT; i++) {
+		if (!minors[i]) {
+			minors[i] = true;
+			return i;
+		}
+	}
+
+	return -EOVERFLOW;
+}
+
+void free_minor(int minor) {
+	minors[minor] = false;
+}
+
 int new_doomdev(struct pci_dev *dev)
 {
 	int err = 0;
@@ -128,16 +145,13 @@ int new_doomdev(struct pci_dev *dev)
 	struct doom_data *doom_data;
 	dev_t devt;
 
-	if (next_minor >= DOOMDEV_COUNT) {
-		return -EOVERFLOW;
-	}
-
 	doom_data = pci_get_drvdata(dev);
 
 	cdev_init(&doom_data->cdev, &doomdev_fops);
 	ORFAIL(cdev_add(&doom_data->cdev, first, 1), error_add);
 
-	minor = next_minor++;
+	minor = alloc_minor();
+	ORFAIL(minor, error_minor);
 	devt = MKDEV(major, minor);
 	doom_data->device = device_create(doom_class, &dev->dev, devt, NULL,
 				"doom%d", minor);
@@ -146,6 +160,8 @@ int new_doomdev(struct pci_dev *dev)
 	return 0;
 
 error_create:
+	free_minor(minor);
+error_minor:
 	cdev_del(&doom_data->cdev);
 error_add:
 	return err;
@@ -153,6 +169,7 @@ error_add:
 
 void destroy_doomdev(struct doom_data *doom_data)
 {
+	free_minor(MINOR(doom_data->device->devt));
 	device_destroy(doom_class, doom_data->device->devt);
 	cdev_del(&doom_data->cdev);
 }