[PATCH] Input: hyperv-keyboard: Use in-place iterator API in the channel callback

[Dexuan Cui <decui@microsoft.com>]

Simplify the ring buffer handling with the in-place API.

Also avoid the dynamic allocation and the memory leak in the channel
callback function.

Signed-off-by: Dexuan Cui <decui@microsoft.com>
---

Hi Dmitry, can this patch go through Sasha's hyperv tree:
https://git.kernel.org/pub/scm/linux/kernel/git/hyperv/linux.git

This is a purely Hyper-V specific change.

 drivers/input/serio/hyperv-keyboard.c | 35 ++++++-----------------------------
 1 file changed, 6 insertions(+), 29 deletions(-)

diff --git a/drivers/input/serio/hyperv-keyboard.c b/drivers/input/serio/hyperv-keyboard.c
index 88ae7c2..e486a8a 100644
--- a/drivers/input/serio/hyperv-keyboard.c
+++ b/drivers/input/serio/hyperv-keyboard.c
@@ -237,40 +237,17 @@ static void hv_kbd_handle_received_packet(struct hv_device *hv_dev,
 
 static void hv_kbd_on_channel_callback(void *context)
 {
+	struct vmpacket_descriptor *desc;
 	struct hv_device *hv_dev = context;
-	void *buffer;
-	int bufferlen = 0x100; /* Start with sensible size */
 	u32 bytes_recvd;
 	u64 req_id;
-	int error;
 
-	buffer = kmalloc(bufferlen, GFP_ATOMIC);
-	if (!buffer)
-		return;
-
-	while (1) {
-		error = vmbus_recvpacket_raw(hv_dev->channel, buffer, bufferlen,
-					     &bytes_recvd, &req_id);
-		switch (error) {
-		case 0:
-			if (bytes_recvd == 0) {
-				kfree(buffer);
-				return;
-			}
-
-			hv_kbd_handle_received_packet(hv_dev, buffer,
-						      bytes_recvd, req_id);
-			break;
+	foreach_vmbus_pkt(desc, hv_dev->channel) {
+		bytes_recvd = desc->len8 * 8;
+		req_id = desc->trans_id;
 
-		case -ENOBUFS:
-			kfree(buffer);
-			/* Handle large packet */
-			bufferlen = bytes_recvd;
-			buffer = kmalloc(bytes_recvd, GFP_ATOMIC);
-			if (!buffer)
-				return;
-			break;
-		}
+		hv_kbd_handle_received_packet(hv_dev, desc, bytes_recvd,
+					      req_id);
 	}
 }
 
-- 
1.8.3.1