firewire: core: use guard macro to maintain isochronous context for userspace client

The core function allows one isochronous contexts per userspace client.
The concurrent access to the context is protected by spinlock in the
instance of client.

This commit uses guard macro to maintain the spinlock.

Link: https://lore.kernel.org/r/20240805085408.251763-12-o-takashi@sakamocchi.jpSigned-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>

drivers/firewire/core-cdev.c

@@ -1062,10 +1062,10 @@ static int ioctl_create_iso_context(struct client *client, union ioctl_arg *arg)
 	if (client->version < FW_CDEV_VERSION_AUTO_FLUSH_ISO_OVERFLOW)
 		context->drop_overflow_headers = true;
 
-	/* We only support one context at this time. */
-	spin_lock_irq(&client->lock);
+	// We only support one context at this time.
+	guard(spinlock_irq)(&client->lock);
+
 	if (client->iso_context != NULL) {
-		spin_unlock_irq(&client->lock);
 		fw_iso_context_destroy(context);
 
 		return -EBUSY;
@@ -1075,7 +1075,6 @@ static int ioctl_create_iso_context(struct client *client, union ioctl_arg *arg)
 					    client->device->card,
 					    iso_dma_direction(context));
 		if (ret < 0) {
-			spin_unlock_irq(&client->lock);
 			fw_iso_context_destroy(context);
 
 			return ret;
@@ -1084,7 +1083,6 @@ static int ioctl_create_iso_context(struct client *client, union ioctl_arg *arg)
 	}
 	client->iso_closure = a->closure;
 	client->iso_context = context;
-	spin_unlock_irq(&client->lock);
 
 	a->handle = 0;
 
@@ -1806,16 +1804,15 @@ static int fw_device_op_mmap(struct file *file, struct vm_area_struct *vma)
 	if (ret < 0)
 		return ret;
 
-	spin_lock_irq(&client->lock);
-	if (client->iso_context) {
-		ret = fw_iso_buffer_map_dma(&client->buffer,
-				client->device->card,
-				iso_dma_direction(client->iso_context));
-		client->buffer_is_mapped = (ret == 0);
+	scoped_guard(spinlock_irq, &client->lock) {
+		if (client->iso_context) {
+			ret = fw_iso_buffer_map_dma(&client->buffer, client->device->card,
+						    iso_dma_direction(client->iso_context));
+			if (ret < 0)
+				goto fail;
+			client->buffer_is_mapped = true;
+		}
 	}
-	spin_unlock_irq(&client->lock);
-	if (ret < 0)
-		goto fail;
 
 	ret = vm_map_pages_zero(vma, client->buffer.pages,
 				client->buffer.page_count);