[PATCH] Input: sur40: prevent polling loop from stalling

When the SUR40 driver receives a packet with no blobs while blobs are
still expected, packet_blobs remains zero and need_blobs is never
decremented.

This causes the polling loop to make no progress.

Return from the polling operation when no blobs are received while
blobs are still expected.

Tested in a VM by reproducing the condition and verifying that the
driver no longer remains in the polling loop.

Fixes: bdb5c57f209c ("Input: add sur40 driver for Samsung SUR40 (aka
MS Surface 2.0/Pixelsense)")

Signed-off-by: Fartman42121cool <redacted>

---
 drivers/input/touchscreen/sur40.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/input/touchscreen/sur40.c

b/drivers/input/touchscreen/sur40.c

--- a/drivers/input/touchscreen/sur40.c
+++ b/drivers/input/touchscreen/sur40.c

@@ -510,6 +510,13 @@ static void sur40_poll(struct input_dev *input)
  if (packet_blobs > need_blobs)
  packet_blobs = need_blobs;

+ if (!packet_blobs && need_blobs) {
+ dev_err(sur40->dev, "received no blobs while %d are still expected\n",
+ need_blobs);
+ return;
+ }
+
+
  for (i = 0; i < packet_blobs; i++) {
  need_blobs--;
  dev_dbg(sur40->dev, "processing blob\n");
  sur40_report_blob(&(inblob[i]), input);