[PATCH 4.4 069/117] usb: cdc-acm: send zero packet for intel 7260 modem

[Greg Kroah-Hartman]

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>

commit ffdb1e369a73b380fce95b05f8498d92c43842b4 upstream.

For Intel 7260 modem, it is needed for host side to send zero
packet if the BULK OUT size is equal to USB endpoint max packet
length. Otherwise, modem side may still wait for more data and
cannot give response to host side.

Signed-off-by: Konrad Leszczynski <konrad.leszczynski@xxxxxxxxx>
Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/usb/class/cdc-acm.c |    6 ++++++
 drivers/usb/class/cdc-acm.h |    1 +
 2 files changed, 7 insertions(+)

--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -1405,6 +1405,8 @@ made_compressed_probe:
 				usb_sndbulkpipe(usb_dev, epwrite->bEndpointAddress),
 				NULL, acm->writesize, acm_write_bulk, snd);
 		snd->urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;
+		if (quirks & SEND_ZERO_PACKET)
+			snd->urb->transfer_flags |= URB_ZERO_PACKET;
 		snd->instance = acm;
 	}
 
@@ -1862,6 +1864,10 @@ static const struct usb_device_id acm_id
 	{ USB_INTERFACE_INFO(USB_CLASS_COMM, USB_CDC_SUBCLASS_ACM,
 		USB_CDC_ACM_PROTO_AT_CDMA) },
 
+	{ USB_DEVICE(0x1519, 0x0452), /* Intel 7260 modem */
+	.driver_info = SEND_ZERO_PACKET,
+	},
+
 	{ }
 };
 
--- a/drivers/usb/class/cdc-acm.h
+++ b/drivers/usb/class/cdc-acm.h
@@ -134,3 +134,4 @@ struct acm {
 #define IGNORE_DEVICE			BIT(5)
 #define QUIRK_CONTROL_LINE_STATE	BIT(6)
 #define CLEAR_HALT_CONDITIONS		BIT(7)
+#define SEND_ZERO_PACKET		BIT(8)