USB: gadget: f_mtp: Zero length packet fixes

Send zero length packets at end of transfers that are a multiple of the
bulk max packet size as required by MTP.

Signed-off-by: Mike Lockwood <lockwood@android.com>

diff --git a/drivers/usb/gadget/f_mtp.c b/drivers/usb/gadget/f_mtp.c
index 03ea4a7..64fe3b3 100644 (file)
--- a/drivers/usb/gadget/f_mtp.c
+++ b/drivers/usb/gadget/f_mtp.c
@@ -540,6 +540,7 @@ static ssize_t mtp_write(struct file *fp, const char __user *buf,
        struct usb_composite_dev *cdev = dev->cdev;
        struct usb_request *req = 0;
        int r = count, xfer;
+       int sendZLP = 0;
        int ret;
 
        DBG(cdev, "mtp_write(%d)\n", count);
@@ -558,8 +559,18 @@ static ssize_t mtp_write(struct file *fp, const char __user *buf,
        dev->state = STATE_BUSY;
        spin_unlock_irq(&dev->lock);
 
-       /* condition check at bottom to allow zero length packet write */
-       do {
+       /* we need to send a zero length packet to signal the end of transfer
+        * if the transfer size is aligned to a packet boundary.
+        */
+       if ((count & (dev->ep_in->maxpacket - 1)) == 0) {
+               sendZLP = 1;
+       }
+
+       while (count > 0 || sendZLP) {
+               /* so we exit after sending ZLP */
+               if (count == 0)
+                       sendZLP = 0;
+
                if (dev->state != STATE_BUSY) {
                        DBG(cdev, "mtp_write dev->error\n");
                        r = -EIO;
@@ -598,7 +609,7 @@ static ssize_t mtp_write(struct file *fp, const char __user *buf,
 
                /* zero this so we don't try to free it on error exit */
                req = 0;
-       } while (count > 0);
+       }
 
        if (req)
                req_put(dev, &dev->tx_idle, req);
@@ -635,11 +646,9 @@ static void send_file_work(struct work_struct *data) {
        DBG(cdev, "send_file_work(%lld %lld)\n", offset, count);
 
        /* we need to send a zero length packet to signal the end of transfer
-        * if the length is > 4 gig and the last packet is aligned to a
-        * packet boundary.
+        * if the transfer size is aligned to a packet boundary.
         */
-       if (dev->xfer_file_length >= 0xFFFFFFFF
-               && (dev->xfer_file_length & (dev->ep_in->maxpacket - 1)) == 0) {
+       if ((dev->xfer_file_length & (dev->ep_in->maxpacket - 1)) == 0) {
                sendZLP = 1;
        }