netdev - [PATCH net-next 2/3] netvsc: add comments about callback's and NAPI

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Date:   Thu, 16 Mar 2017 16:12:38 -0700
From:   Stephen Hemminger <stephen@...workplumber.org>
To:     kys@...rosoft.com, davem@...emloft.net, haiyangz@...rosoft.com
Cc:     netdev@...r.kernel.org, Stephen Hemminger <sthemmin@...rosoft.com>
Subject: [PATCH net-next 2/3] netvsc: add comments about callback's and NAPI

Add some short description of how callback's and NAPI interoperate.

Signed-off-by: Stephen Hemminger <sthemmin@...rosoft.com>
---
 drivers/net/hyperv/netvsc.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/net/hyperv/netvsc.c b/drivers/net/hyperv/netvsc.c
index 0a2e9bd98d2c..989b7cd99380 100644
--- a/drivers/net/hyperv/netvsc.c
+++ b/drivers/net/hyperv/netvsc.c
@@ -1209,6 +1209,10 @@ static struct hv_device *netvsc_channel_to_device(struct vmbus_channel *channel)
 	return primary ? primary->device_obj : channel->device_obj;
 }
 
+/* Network processing softirq
+ * Process data in incoming ring buffer from host
+ * Stops when ring is empty or budget is met or exceeded.
+ */
 int netvsc_poll(struct napi_struct *napi, int budget)
 {
 	struct netvsc_channel *nvchan
@@ -1238,7 +1242,11 @@ int netvsc_poll(struct napi_struct *napi, int budget)
 	}
 	hv_pkt_iter_close(channel);
 
-	/* If ring is empty and NAPI is not doing polling */
+	/* If budget was not exhausted and
+	 * not doing busy poll
+	 * then re-enable host interrupts
+	 *  and reschedule if ring is not empty.
+	 */
 	if (work_done < budget &&
 	    napi_complete_done(napi, work_done) &&
 	    hv_end_read(&channel->inbound) != 0)
@@ -1248,6 +1256,9 @@ int netvsc_poll(struct napi_struct *napi, int budget)
 	return work_done;
 }
 
+/* Call back when data is available in host ring buffer.
+ * Processing is deferred until network softirq (NAPI)
+ */
 void netvsc_channel_cb(void *context)
 {
 	struct netvsc_channel *nvchan = context;
-- 
2.11.0