From 2e25134122c25ebb0679b4bbd536fb46c669f9d7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20Gl=C3=B6ckner?= <dg@emlix.com>
Date: Thu, 28 May 2009 12:53:24 +0200
Subject: [PATCH] USB: gadget: g_serial: append zlp when tx buffer becomes
 empty
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Some usb serial host drivers expect a short packet before they forward
the data to the application. This is caused by them trying to read more
than one packet at a time. So when the gadget sends an exact multiple
of the maximum packet size, it should append a zero-length packet.

Signed-off-by: Daniel Glöckner <dg@emlix.com>
Cc: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---
 drivers/usb/gadget/u_serial.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/usb/gadget/u_serial.c b/drivers/usb/gadget/u_serial.c
index 0a4d99ab40d8c0..fc6e709f45b1b1 100644
--- a/drivers/usb/gadget/u_serial.c
+++ b/drivers/usb/gadget/u_serial.c
@@ -371,6 +371,7 @@ __acquires(&port->port_lock)
 
 		req->length = len;
 		list_del(&req->list);
+		req->zero = (gs_buf_data_avail(&port->port_write_buf) == 0);
 
 		pr_vdebug(PREFIX "%d: tx len=%d, 0x%02x 0x%02x 0x%02x ...\n",
 				port->port_num, len, *((u8 *)req->buf),
-- 
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