From 1536af0c020ef41859ad52a79ffeda0b43514718 Mon Sep 17 00:00:00 2001
From: Andrew Waterman <waterman@eecs.berkeley.edu>
Date: Fri, 17 Feb 2012 16:36:00 -0800
Subject: [PATCH] implement lighter-weight htif packet header

---
 riscv/htif.cc | 54 +++++++++++++++++++++++++--------------------------
 riscv/htif.h  |  4 ++--
 2 files changed, 29 insertions(+), 29 deletions(-)

diff --git a/riscv/htif.cc b/riscv/htif.cc
index 7de27c6..d439f7b 100644
--- a/riscv/htif.cc
+++ b/riscv/htif.cc
@@ -21,14 +21,15 @@ enum
   APP_CMD_NACK
 };
 
-#define APP_DATA_ALIGN 8
 #define APP_MAX_DATA_SIZE 1024
+#define HTIF_DATA_ALIGN 8
 struct packet
 {
-  uint16_t cmd;
-  uint16_t seqno;
-  uint32_t data_size;
-  uint64_t addr;
+  reg_t cmd       :  4;
+  reg_t data_size : 12;
+  reg_t seqno     :  8;
+  reg_t addr      : 40;
+
   uint8_t  data[APP_MAX_DATA_SIZE];
 };
 
@@ -65,18 +66,19 @@ void htif_t::wait_for_fromhost_write()
 
 void htif_t::send_packet(packet* p)
 {
-  int bytes = write(tohost_fd,p,offsetof(packet,data)+p->data_size);
-  if((size_t)bytes != offsetof(packet,data) + p->data_size)
+  size_t data_size = p->data_size*HTIF_DATA_ALIGN;
+  size_t bytes = write(tohost_fd, p, offsetof(packet,data) + data_size);
+  if(bytes != offsetof(packet,data) + data_size)
   {
-    const char* error = bytes == -1 ? strerror(errno) : "not all bytes sent";
+    const char* error = (ssize_t)bytes == -1 ? strerror(errno) : "not all bytes sent";
     fprintf(stderr,"HTIF error: %s\n", error);
     exit(-1);
   }
 }
 
-void htif_t::nack(uint16_t nack_seqno)
+void htif_t::nack(uint8_t nack_seqno)
 {
-  packet p = {APP_CMD_NACK,nack_seqno,0,0};
+  packet p = {APP_CMD_NACK,0,nack_seqno,0};
   send_packet(&p);
 }
 
@@ -110,7 +112,7 @@ int htif_t::wait_for_packet()
       continue;
     }
 
-    packet ackpacket = {APP_CMD_ACK,seqno,0,0};
+    packet ackpacket = {APP_CMD_ACK,0,seqno,0};
 
     switch(p.cmd)
     {
@@ -120,34 +122,32 @@ int htif_t::wait_for_packet()
         sim->stop();
         break;
       case APP_CMD_READ_MEM:
-        assert(p.addr % APP_DATA_ALIGN == 0);
-        assert(p.data_size % APP_DATA_ALIGN == 0);
-        assert(p.data_size <= APP_MAX_DATA_SIZE);
-        assert(p.addr <= sim->memsz && p.addr+p.data_size <= sim->memsz);
+        assert(p.data_size <= APP_MAX_DATA_SIZE/HTIF_DATA_ALIGN);
+        assert(p.addr < sim->memsz/HTIF_DATA_ALIGN);
+        assert(p.addr+p.data_size <= sim->memsz/HTIF_DATA_ALIGN);
         ackpacket.data_size = p.data_size;
 
-        static_assert(APP_DATA_ALIGN >= sizeof(uint64_t))
-        for(size_t i = 0; i < p.data_size/8; i++)
-          ((uint64_t*)ackpacket.data)[i] = sim->mmu->load_uint64(p.addr+i*8);
+        assert(HTIF_DATA_ALIGN == sizeof(uint64_t));
+        for(size_t i = 0; i < p.data_size; i++)
+          ((uint64_t*)ackpacket.data)[i] = sim->mmu->load_uint64((p.addr+i)*HTIF_DATA_ALIGN);
         break;
       case APP_CMD_WRITE_MEM:
-        assert(p.addr % APP_DATA_ALIGN == 0);
-        assert(p.data_size % APP_DATA_ALIGN == 0);
-        assert(p.data_size <= bytes - offsetof(packet,data));
-        assert(p.addr <= sim->memsz && p.addr+p.data_size <= sim->memsz);
+        assert(p.data_size*HTIF_DATA_ALIGN <= bytes - offsetof(packet,data));
+        assert(p.addr < sim->memsz/HTIF_DATA_ALIGN);
+        assert(p.addr+p.data_size <= sim->memsz/HTIF_DATA_ALIGN);
 
-        for(size_t i = 0; i < p.data_size/8; i++)
-          sim->mmu->store_uint64(p.addr+i*8, ((uint64_t*)p.data)[i]);
+        for(size_t i = 0; i < p.data_size; i++)
+          sim->mmu->store_uint64((p.addr+i)*HTIF_DATA_ALIGN, ((uint64_t*)p.data)[i]);
         break;
       case APP_CMD_READ_CONTROL_REG:
         assert(p.addr == 16);
-        assert(p.data_size == sizeof(reg_t));
-        ackpacket.data_size = sizeof(reg_t);
+        assert(p.data_size == 1);
+        ackpacket.data_size = 1;
         memcpy(ackpacket.data,&sim->tohost,sizeof(reg_t));
         break;
       case APP_CMD_WRITE_CONTROL_REG:
         assert(p.addr == 17);
-        assert(p.data_size == sizeof(reg_t));
+        assert(p.data_size == 1);
         sim->tohost = 0;
         memcpy(&sim->fromhost,p.data,sizeof(reg_t));
         break;
diff --git a/riscv/htif.h b/riscv/htif.h
index 805cc4f..792d840 100644
--- a/riscv/htif.h
+++ b/riscv/htif.h
@@ -29,9 +29,9 @@ private:
   sim_t* sim;
   int tohost_fd;
   int fromhost_fd;
-  uint16_t seqno;
+  uint8_t seqno;
 
-  void nack(uint16_t seqno);
+  void nack(uint8_t seqno);
   void send_packet(packet* p);
   int wait_for_packet();
 };
-- 
2.30.2