[PATCH 17/18] xen/sndfront: use xenbus_setup_ring() and xenbus_teardown_ring()

[Juergen Gross <jgross@xxxxxxxx>]

Simplify sndfront's ring creation and removal via xenbus_setup_ring()
and xenbus_teardown_ring().

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
 sound/xen/xen_snd_front_evtchnl.c | 41 +++++++------------------------
 1 file changed, 9 insertions(+), 32 deletions(-)

diff --git a/sound/xen/xen_snd_front_evtchnl.c b/sound/xen/xen_snd_front_evtchnl.c
index 3e21369c8216..32d42fd3f7ac 100644
--- a/sound/xen/xen_snd_front_evtchnl.c
+++ b/sound/xen/xen_snd_front_evtchnl.c
@@ -143,12 +143,12 @@ void xen_snd_front_evtchnl_flush(struct xen_snd_front_evtchnl *channel)
 static void evtchnl_free(struct xen_snd_front_info *front_info,
 			 struct xen_snd_front_evtchnl *channel)
 {
-	unsigned long page = 0;
+	void *page = NULL;
 
 	if (channel->type == EVTCHNL_TYPE_REQ)
-		page = (unsigned long)channel->u.req.ring.sring;
+		page = channel->u.req.ring.sring;
 	else if (channel->type == EVTCHNL_TYPE_EVT)
-		page = (unsigned long)channel->u.evt.page;
+		page = channel->u.evt.page;
 
 	if (!page)
 		return;
@@ -167,10 +167,7 @@ static void evtchnl_free(struct xen_snd_front_info *front_info,
 		xenbus_free_evtchn(front_info->xb_dev, channel->port);
 
 	/* End access and free the page. */
-	if (channel->gref != INVALID_GRANT_REF)
-		gnttab_end_foreign_access(channel->gref, page);
-	else
-		free_page(page);
+	xenbus_teardown_ring(&page, 1, &channel->gref);
 
 	memset(channel, 0, sizeof(*channel));
 }
@@ -196,8 +193,7 @@ static int evtchnl_alloc(struct xen_snd_front_info *front_info, int index,
 			 enum xen_snd_front_evtchnl_type type)
 {
 	struct xenbus_device *xb_dev = front_info->xb_dev;
-	unsigned long page;
-	grant_ref_t gref;
+	void *page;
 	irq_handler_t handler;
 	char *handler_name = NULL;
 	int ret;
@@ -207,12 +203,9 @@ static int evtchnl_alloc(struct xen_snd_front_info *front_info, int index,
 	channel->index = index;
 	channel->front_info = front_info;
 	channel->state = EVTCHNL_STATE_DISCONNECTED;
-	channel->gref = INVALID_GRANT_REF;
-	page = get_zeroed_page(GFP_KERNEL);
-	if (!page) {
-		ret = -ENOMEM;
+	ret = xenbus_setup_ring(xb_dev, GFP_KERNEL, &page, 1, &channel->gref);
+	if (ret)
 		goto fail;
-	}
 
 	handler_name = kasprintf(GFP_KERNEL, "%s-%s", XENSND_DRIVER_NAME,
 				 type == EVTCHNL_TYPE_REQ ?
@@ -226,33 +219,19 @@ static int evtchnl_alloc(struct xen_snd_front_info *front_info, int index,
 	mutex_init(&channel->ring_io_lock);
 
 	if (type == EVTCHNL_TYPE_REQ) {
-		struct xen_sndif_sring *sring = (struct xen_sndif_sring *)page;
+		struct xen_sndif_sring *sring = page;
 
 		init_completion(&channel->u.req.completion);
 		mutex_init(&channel->u.req.req_io_lock);
 		SHARED_RING_INIT(sring);
 		FRONT_RING_INIT(&channel->u.req.ring, sring, XEN_PAGE_SIZE);
 
-		ret = xenbus_grant_ring(xb_dev, sring, 1, &gref);
-		if (ret < 0) {
-			channel->u.req.ring.sring = NULL;
-			goto fail;
-		}
-
 		handler = evtchnl_interrupt_req;
 	} else {
-		ret = gnttab_grant_foreign_access(xb_dev->otherend_id,
-						  virt_to_gfn((void *)page), 0);
-		if (ret < 0)
-			goto fail;
-
-		channel->u.evt.page = (struct xensnd_event_page *)page;
-		gref = ret;
+		channel->u.evt.page = page;
 		handler = evtchnl_interrupt_evt;
 	}
 
-	channel->gref = gref;
-
 	ret = xenbus_alloc_evtchn(xb_dev, &channel->port);
 	if (ret < 0)
 		goto fail;
@@ -279,8 +258,6 @@ static int evtchnl_alloc(struct xen_snd_front_info *front_info, int index,
 	return 0;
 
 fail:
-	if (page)
-		free_page(page);
 	kfree(handler_name);
 	dev_err(&xb_dev->dev, "Failed to allocate ring: %d\n", ret);
 	return ret;
-- 
2.34.1