From d6cd95d3685174e2e73140db4e0102ee7336953e Mon Sep 17 00:00:00 2001
From: dullfire <dullfire@yahoo.com>
Date: Tue, 23 Feb 2021 17:08:10 -0600
Subject: [PATCH] Add windowing support. this gets us up to ~8KiB/s tranfers
 speeds!

---
 litex/soc/software/bios/kermit-client.c | 35 +++++++++++++++----------
 1 file changed, 21 insertions(+), 14 deletions(-)

diff --git a/litex/soc/software/bios/kermit-client.c b/litex/soc/software/bios/kermit-client.c
index c3aee461..9990c508 100644
--- a/litex/soc/software/bios/kermit-client.c
+++ b/litex/soc/software/bios/kermit-client.c
@@ -100,7 +100,27 @@ static inline int handle_pkt_S(struct mini_kerm_sm *sm, uint8_t * buffer)
     /* Error out on non standard ops. this makes the parsing MUCH easier */
     if (sm->line_opts.QCTL != '#')
         return -1;
-    return 0;
+    static uint8_t resp[] =
+        "\x01\0\0Y\0      1 \0\0";
+    static const size_t resp_size = sizeof(resp);
+    resp[1] = tochar(resp_size - 2);
+    resp[2] = buffer[2];
+    resp[4] = tochar(94);
+    /* capps */
+    resp[13] = tochar(2);
+    /* window size
+     * we allow two inback packets at a time*/
+    resp[14] = tochar(4);
+    /* Adding extended packet length migh be good as well, but it requires changes
+     * to both checksuming, and packet length detect, where as windowing only require
+     * advertising support.*/
+    /* Again, note that this stomps the 'null' terminator, because this is not a c-string */
+    resp[resp_size - 1] = gen_ori_check(resp);
+    size_t i = 0;
+    sendbyte(-1, '\n');
+    for (i = 0; i < resp_size; i++)
+        sendbyte(-1, resp[i]);
+    sendbyte(-1, '\n');
 }
 
 /* The 'F' packet is a no-op.
@@ -183,7 +203,6 @@ static inline int handle_pkt_D(struct mini_kerm_sm *sm, uint8_t * buffer)
 }
 
 bool kermit_valid_packet(uint8_t *buffer, size_t len);
-//static int kermit_get_file(struct mini_kerm_sm *sm, uint8_t *buffer, size_t buffer_index)
 static int kermit_get_file(struct mini_kerm_sm *sm, uint8_t mark)
 {
     /*
@@ -193,17 +212,11 @@ static int kermit_get_file(struct mini_kerm_sm *sm, uint8_t mark)
      * 1 = the handler took care of any needed resonse
      */
     int success = -1;
-#if 0
-    bool have_whole_pkt = kermit_valid_packet(buffer, buffer_index);
-    if (have_whole_pkt)
-        goto whole_pkt_start;
-#else
     uint8_t *buffer = sm->pkt_buffer;
     size_t buffer_index = 0;
     bool have_whole_pkt = false;
     if (mark == 1)
         buffer[buffer_index++] = mark;
-#endif
 
     while (true)
     {
@@ -225,11 +238,6 @@ static int kermit_get_file(struct mini_kerm_sm *sm, uint8_t mark)
         if (!check_pkt(buffer))
             buffer[3] = 0;
 
-#if 0
-whole_pkt_start:
-        printf("found packet len/seq/type %02x/%02x/%c\n",
-                unchar(buffer[1]), unchar(buffer[2]), buffer[3]);
-#endif
 
         switch (buffer[3]) {
             case 'S':
@@ -369,7 +377,6 @@ int kermit_maybe(uint8_t mark)
     if (mark != 1)
         return -1;
     struct mini_kerm_sm *sm = init_kermit_sm();
-    //printf("Placing output buffer @0x%p\n", sm->outbuffer_base);
     /* boot should'nt return */
     if (!kermit_get_file(sm, mark))
         boot(0, 0, 0, sm->outbuffer_base);
-- 
2.30.2