From 5e355a4f0588438632d56e2f9fef5a75b949bd24 Mon Sep 17 00:00:00 2001
From: Christian Starkjohann <cs+github@obdev.at>
Date: Wed, 5 Dec 2012 22:57:13 +0100
Subject: usbMsgPtr now has a separate type so that it can be defined to an 8
 bit type for tiny memory model

---
 usbdrv/usbconfig-prototype.h |  9 +++++++++
 usbdrv/usbdrv.c              | 12 +++++++-----
 usbdrv/usbdrv.h              | 13 ++++++++++++-
 3 files changed, 28 insertions(+), 6 deletions(-)

diff --git a/usbdrv/usbconfig-prototype.h b/usbdrv/usbconfig-prototype.h
index 826f026..f9cdd91 100644
--- a/usbdrv/usbconfig-prototype.h
+++ b/usbdrv/usbconfig-prototype.h
@@ -356,6 +356,15 @@ section at the end of this file).
 #define USB_CFG_DESCR_PROPS_HID_REPORT              0
 #define USB_CFG_DESCR_PROPS_UNKNOWN                 0
 
+
+#define usbMsgPtr_t unsigned short
+/* If usbMsgPtr_t is not defined, it defaults to 'uchar *'. We define it to
+ * a scalar type here because gcc generates slightly shorter code for scalar
+ * arithmetics than for pointer arithmetics. Remove this define for backward
+ * type compatibility or define it to an 8 bit type if you use data in RAM only
+ * and all RAM is below 256 bytes (tiny memory model in IAR CC).
+ */
+
 /* ----------------------- Optional MCU Description ------------------------ */
 
 /* The following configurations have working defaults in usbdrv.h. You
diff --git a/usbdrv/usbdrv.c b/usbdrv/usbdrv.c
index 7a125f2..e58d764 100644
--- a/usbdrv/usbdrv.c
+++ b/usbdrv/usbdrv.c
@@ -45,7 +45,7 @@ uchar       usbCurrentDataToken;/* when we check data toggling to ignore duplica
 #endif
 
 /* USB status registers / not shared with asm code */
-uchar               *usbMsgPtr;     /* data to transmit next -- ROM or RAM address */
+usbMsgPtr_t         usbMsgPtr;      /* data to transmit next -- ROM or RAM address */
 static usbMsgLen_t  usbMsgLen = USB_NO_MSG; /* remaining number of bytes */
 static uchar        usbMsgFlags;    /* flag values see below */
 
@@ -301,7 +301,7 @@ USB_PUBLIC void usbSetInterrupt3(uchar *data, uchar len)
             len = usbFunctionDescriptor(rq);        \
         }else{                                      \
             len = USB_PROP_LENGTH(cfgProp);         \
-            usbMsgPtr = (uchar *)(staticName);      \
+            usbMsgPtr = (usbMsgPtr_t)(staticName);  \
         }                                           \
     }
 
@@ -409,7 +409,7 @@ uchar   index = rq->wIndex.bytes[0];
     SWITCH_DEFAULT                          /* 7=SET_DESCRIPTOR, 12=SYNC_FRAME */
         /* Should we add an optional hook here? */
     SWITCH_END
-    usbMsgPtr = dataPtr;
+    usbMsgPtr = (usbMsgPtr_t)dataPtr;
 skipMsgPtrAssignment:
     return len;
 }
@@ -499,7 +499,8 @@ static uchar usbDeviceRead(uchar *data, uchar len)
         }else
 #endif
         {
-            uchar i = len, *r = usbMsgPtr;
+            uchar i = len;
+            usbMsgPtr_t r = usbMsgPtr;
             if(usbMsgFlags & USB_FLG_MSGPTR_IS_ROM){    /* ROM data */
                 do{
                     uchar c = USB_READ_FLASH(r);    /* assign to char size variable to enforce byte ops */
@@ -508,7 +509,8 @@ static uchar usbDeviceRead(uchar *data, uchar len)
                 }while(--i);
             }else{  /* RAM data */
                 do{
-                    *data++ = *r++;
+                    *data++ = *((uchar *)r);
+                    r++;
                 }while(--i);
             }
             usbMsgPtr = r;
diff --git a/usbdrv/usbdrv.h b/usbdrv/usbdrv.h
index 6d1ad50..b377c43 100644
--- a/usbdrv/usbdrv.h
+++ b/usbdrv/usbdrv.h
@@ -163,6 +163,17 @@ USB messages, even if they address another (low-speed) device on the same bus.
  */
 #define USB_NO_MSG  ((usbMsgLen_t)-1)   /* constant meaning "no message" */
 
+#ifndef usbMsgPtr_t
+#define usbMsgPtr_t uchar *
+#endif
+/* Making usbMsgPtr_t a define allows the user of this library to define it to
+ * an 8 bit type on tiny devices. This reduces code size, especially if the
+ * compiler supports a tiny memory model.
+ * The type can be a pointer or scalar type, casts are made where necessary.
+ * Although it's paradoxical, Gcc 4 generates slightly better code for scalar
+ * types than for pointers.
+ */
+
 struct usbRequest;  /* forward declaration */
 
 USB_PUBLIC void usbInit(void);
@@ -178,7 +189,7 @@ USB_PUBLIC void usbPoll(void);
  * Please note that debug outputs through the UART take ~ 0.5ms per byte
  * at 19200 bps.
  */
-extern uchar *usbMsgPtr;
+extern usbMsgPtr_t usbMsgPtr;
 /* This variable may be used to pass transmit data to the driver from the
  * implementation of usbFunctionWrite(). It is also used internally by the
  * driver for standard control requests.
-- 
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