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authorTat-Chee Wan (USM)2011-03-22 15:27:49 +0800
committerTat-Chee Wan (USM)2011-03-22 15:27:49 +0800
commit39f866e05f703d64f621d77b135b7958d0ccf110 (patch)
tree1ebdc91ddb8f09ca8371635ac7163d22300b2fb9
parentcb09675818731776be4129ba19fb90e299c130aa (diff)
clarified comments regarding usb and gdb message formats
-rw-r--r--Debugger/debug_comm.S25
-rw-r--r--Debugger/debug_stub.h4
2 files changed, 17 insertions, 12 deletions
diff --git a/Debugger/debug_comm.S b/Debugger/debug_comm.S
index a43cc5f..75f835e 100644
--- a/Debugger/debug_comm.S
+++ b/Debugger/debug_comm.S
@@ -338,14 +338,16 @@ _exit_conv_ascii2byte:
* Byte 3-N: Message data | GDB Command
*
* The GDB Command (of size M) has the following format:
- * Offset 0: '$'
- * Offset 1: GDB Command char
- * Offset 2 - (M-4): Command packet info
+ * Offset 0: '+'/'-' Command Received Status (Optional)
+ * Offset 1/0: '$'
+ * Offset 2/1: GDB Command char
+ * Offset 3 - (M-4): Command packet info
* Offset M-3: '#'
* Offset M-2: MSB of Checksum
* Offset M-1: LSB of Checksum
*
- * The maximum size of a GDB Command packet is MSGBUF_SIZE - 4 ('$', '#', 2 byte checksum)
+ * To be safe, we assume that the Command Received Status is always sent by the GDB server. Therefore,
+ * The maximum size of a GDB Command packet is MSGBUF_SIZE - 5 ('+'/'-', '$', '#', 2 byte checksum)
*
* GDB Response
* ============
@@ -354,15 +356,18 @@ _exit_conv_ascii2byte:
* Byte 2: Telegram Size (Len of USB Buffer - 3, max is MSG_SEGMENTSIZE) |
* Byte 3-N: Message data | GDB Response
*
+ * The GDB Retransmission Request has the following format:
+ * Offset 0: '-' Command Received Status
+ *
* The GDB Response (of size M) has the following format:
- * Offset 0: '+' or '-' Command Received Status
+ * Offset 0: '+' Command Received Status
* Offset 1: '$'
* Offset 2 - (M-4): Response packet info
* Offset M-3: '#'
* Offset M-2: MSB of Checksum
* Offset M-1: LSB of Checksum
*
- * The maximum size of a GDB Response packet is MSGBUF_SIZE - 5 ('-'/'+', '$', '#', 2 byte checksum)
+ * The maximum size of a GDB Response packet is MSGBUF_SIZE - 5 ('+', '$', '#', 2 byte checksum)
*
* Note: The Telegram Size is the actual size of the Message Data portion
* (i.e., excludes the three header bytes, includes the GDB Command/Response Packet checksum bytes
@@ -723,7 +728,7 @@ _exit_copy_msg_to_usbbuf:
* On exit:
* r0: status (0: success, -1: error)
* Note: GDB Message to be sent must be ASCIIZ terminated, does not include '#' and checksum
- * Response packets start with '+'/'-' followed by '$' (2 bytes prefix)
+ * Response packets start with '+' followed by '$' (2 bytes prefix)
*/
dbg__putDebugMsg:
stmfd sp!, {r4,r5,lr}
@@ -731,8 +736,8 @@ dbg__putDebugMsg:
ldr r5, =debug_msgTxBufPtr /* R5: data structure base pointer */
ldr r4, [r5] /* Tx buffer Start Address */
str r4, [r5, #TXAPPENDPTR_OFFSET] /* Reset Tx buffer Append Pointer */
- add r0, r4, #2 /* skip '+'/'-' and '$' */
- bl _msgbuf_checksum /* R2: length (excl '+'/'-' and '$'), R1: calculated checksum, R0: pointer to checksum in tx buffer */
+ add r0, r4, #2 /* skip '+' and '$' */
+ bl _msgbuf_checksum /* R2: length (excl '+' and '$'), R1: calculated checksum, R0: pointer to checksum in tx buffer */
#ifdef CHECK_TXLEN
add r2, r2, #2 /* r2: returned length from _msgbuf_checksum, added with prefix length */
@@ -744,7 +749,7 @@ dbg__putDebugMsg:
mov r3, #MSGBUF_CHKSUMCHAR
strb r3, [r0, #-1] /* Insert '#' */
bl byte2ascii /* On return, R0 points to location after checksum bytes, R1 is original pointer to checksum */
- sub r4, r0, r4 /* R4 = Calculated total message length (incl '+'/'-' and '$', '#' and checksum bytes */
+ sub r4, r0, r4 /* R4 = Calculated total message length (incl '+' and '$', '#' and checksum bytes */
cmp r4, #MSG_SEGMENTSIZE /* If total message length > MSG_SEGMENTSIZE */
mov r1, #0 /* Initialize Segment Number = 0 (last segment) first */
mov r0, #0 /* Initial cummulative message length */
diff --git a/Debugger/debug_stub.h b/Debugger/debug_stub.h
index 67f86c4..e39fc8e 100644
--- a/Debugger/debug_stub.h
+++ b/Debugger/debug_stub.h
@@ -50,8 +50,8 @@
#define MSG_SEGMENTSIZE (USB_BUFSIZE - USB_GDBMSG_START) /* 61 bytes per segment */
#define MSGBUF_SIZE (MSG_SEGMENTSIZE*MSG_NUMSEGMENTS) /* Debug Message Buffer Size, 61 x 3 = 183 chars = ~80 bytes of actual data */
#define MSGBUF_CHKSUMOFFSET 3 /* to be subtracted from message length */
-#define MSGBUF_IN_OVERHEADLEN 5 /* For calculating max message data length (include ASCIIZ char) */
-#define MSGBUF_OUT_OVERHEADLEN 6 /* For calculating max message data length (include ASCIIZ char) */
+#define MSGBUF_IN_OVERHEADLEN 5 /* For calculating max message data length (exclude ASCIIZ char) */
+#define MSGBUF_OUT_OVERHEADLEN 5 /* For calculating max message data length (exclude ASCIIZ char) */
#define MSGBUF_CTRLC 0x03 /* For Out of Band Signaling: not implemented yet */
#define MSGBUF_STARTCHAR '$'