From 2c1ea139e754820b55f58bdc32f3376671c453db Mon Sep 17 00:00:00 2001
From: Vladimir 'phcoder' Serbinenko <phcoder@gmail.com>
Date: Sun, 20 Jan 2013 22:45:53 +0100
Subject: [PATCH 120/482] 	Split long USB transfers into short ones.

---
 ChangeLog                    |  4 ++++
 grub-core/bus/usb/usbtrans.c | 20 ++++++++++++++++----
 include/grub/usbtrans.h      |  2 ++
 3 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 4d09825..c8edf73 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+2013-01-20  Aleš Nesrsta  <starous@volny.cz>
+
+	Split long USB transfers into short ones.
+
 2013-01-20  Andrey Borzenkov <arvidjaar@gmail.com>
 
 	* docs/grub.texi (Simple configuration): Clarify GRUB_HIDDEN_TIMEOUT
diff --git a/grub-core/bus/usb/usbtrans.c b/grub-core/bus/usb/usbtrans.c
index 167fae5..154c72d 100644
--- a/grub-core/bus/usb/usbtrans.c
+++ b/grub-core/bus/usb/usbtrans.c
@@ -351,11 +351,23 @@ grub_usb_err_t
 grub_usb_bulk_read (grub_usb_device_t dev,
 		    int endpoint, grub_size_t size, char *data)
 {
-  grub_size_t actual;
+  grub_size_t actual, transferred;
   grub_usb_err_t err;
-  err = grub_usb_bulk_readwrite (dev, endpoint, size, data,
-				 GRUB_USB_TRANSFER_TYPE_IN, 1000, &actual);
-  if (!err && actual != size)
+  grub_size_t current_size, position;
+
+  for (position = 0, transferred = 0;
+       position < size; position += MAX_USB_TRANSFER_LEN)
+    {
+      current_size = size - position;
+      if (current_size >= MAX_USB_TRANSFER_LEN)
+	current_size = MAX_USB_TRANSFER_LEN;
+      err = grub_usb_bulk_readwrite (dev, endpoint, current_size,
+              &data[position], GRUB_USB_TRANSFER_TYPE_IN, 1000, &actual);
+      transferred += actual;
+      if (err || (current_size != actual) ) break;
+    }
+
+  if (!err && transferred != size)
     err = GRUB_USB_ERR_DATA;
   return err;
 }
diff --git a/include/grub/usbtrans.h b/include/grub/usbtrans.h
index 5ee276d..5429007 100644
--- a/include/grub/usbtrans.h
+++ b/include/grub/usbtrans.h
@@ -19,6 +19,8 @@
 #ifndef	GRUB_USBTRANS_H
 #define	GRUB_USBTRANS_H	1
 
+#define MAX_USB_TRANSFER_LEN 0x0800
+
 typedef enum
   {
     GRUB_USB_TRANSFER_TYPE_IN,
-- 
1.8.2.1