fastboot: add preflash command to help with large downloads+flash

Without the partition name, the bootloader would have to store all
of the data until the next flash command, which potentially wastes
time.
To help the bootloader deal with the data more efficiently, we now
issue a flashing hint ("preflash:%s", partname).
"preflash:" is used to indicate that the following download
should ignore any previous "preflash:%s".

Bug: 6045918
Change-Id: I4e9708f64f28a4781bde14eb3714d36b281ec5be

2 files changed, 21 insertions, 10 deletions

diff --git a/fastboot/engine.c b/fastboot/engine.c
index 8d46991..4045759 100644
--- a/fastboot/engine.c
+++ b/fastboot/engine.c
@@ -76,6 +76,7 @@ char *mkmsg(const char *fmt, ...)
 #define OP_NOTICE     4
 #define OP_FORMAT     5
 #define OP_DOWNLOAD_SPARSE 6
+#define OP_COMMAND_IGNORE_FAIL 7
 
 typedef struct Action Action;
 
@@ -374,6 +375,8 @@ int fb_format(Action *a, usb_handle *usb, int skip_if_not_supported)
 
     // Following piece of code is similar to fb_queue_flash() but executes
     // actions directly without queuing
+    snprintf(cmd, sizeof(cmd), "preflash:%s", partition);
+    fb_command(usb, cmd);  /* Ignore status */
     fprintf(stderr, "sending '%s' (%lli KB)...\n", partition, image.image_size/1024);
     status = fb_download_data(usb, image.buffer, image.image_size);
     if (status) goto cleanup;
@@ -402,6 +405,8 @@ void fb_queue_flash(const char *ptn, void *data, unsigned sz)
 {
     Action *a;
 
+    a = queue_action(OP_COMMAND_IGNORE_FAIL, "preflash:%s", ptn);
+    a->msg = mkmsg("prep for '%s' (%d KB)", ptn, sz / 1024);
     a = queue_action(OP_DOWNLOAD, "");
     a->data = data;
     a->size = sz;
@@ -415,6 +420,8 @@ void fb_queue_flash_sparse(const char *ptn, struct sparse_file *s, unsigned sz)
 {
     Action *a;
 
+    a = queue_action(OP_COMMAND_IGNORE_FAIL, "preflash:%s", ptn);
+    a->msg = mkmsg("prep for sparse '%s' (%d KB)", ptn, sz / 1024);
     a = queue_action(OP_DOWNLOAD_SPARSE, "");
     a->data = s;
     a->size = 0;
@@ -575,7 +582,9 @@ void fb_queue_command(const char *cmd, const char *msg)
 
 void fb_queue_download(const char *name, void *data, unsigned size)
 {
-    Action *a = queue_action(OP_DOWNLOAD, "");
+    Action *a;
+    a = queue_action(OP_COMMAND_IGNORE_FAIL, "preflash:");
+    a = queue_action(OP_DOWNLOAD, "");
     a->data = data;
     a->size = size;
     a->msg = mkmsg("downloading '%s'", name);
@@ -614,6 +623,8 @@ int fb_execute_queue(usb_handle *usb)
             status = fb_command(usb, a->cmd);
             status = a->func(a, status, status ? fb_get_error() : "");
             if (status) break;
+        } else if (a->op == OP_COMMAND_IGNORE_FAIL) {
+            fb_command(usb, a->cmd);   /* Ignore status */
         } else if (a->op == OP_QUERY) {
             status = fb_command_response(usb, a->cmd, resp);
             status = a->func(a, status, status ? fb_get_error() : resp);
diff --git a/fastboot/fastboot_protocol.txt b/fastboot/fastboot_protocol.txt
index 2248992..eede5d1 100644
--- a/fastboot/fastboot_protocol.txt
+++ b/fastboot/fastboot_protocol.txt
@@ -1,5 +1,5 @@
 
-FastBoot  Version  0.4
+FastBoot  Version  0.4++
 ----------------------
 
 The fastboot protocol is a mechanism for communicating with bootloaders
@@ -67,10 +67,6 @@ Transport and Framing
 Example Session
 ---------------
 
-Host:    "getvar:version"        request version variable
-
-Client:  "OKAY0.4"               return version "0.4"
-
 Host:    "getvar:nonexistant"    request some undefined variable
 
 Client:  "OKAY"                  return value ""
@@ -123,6 +119,11 @@ Command Reference
   "flash:%s"           Write the previously downloaded image to the
                        named partition (if possible).
 
+  "preflash:%s"        Optionally prepare for a download + flash.
+                       E.g. flash directly during download. To deal with a
+                       failed "flash" followed by a "boot", we send
+                       "preflash:".
+
   "erase:%s"           Erase the indicated partition (clear to 0xFFs)
 
   "boot"               The previously downloaded data is a boot.img
@@ -140,7 +141,9 @@ Command Reference
 
   "powerdown"          Power off the device.
 
-
+* Note about sparse files
+  Large files can be split up using libsparse, and sent to the bootloader
+  as repeated chunks of "download:%08x" + "flash:%s".
 
 Client Variables
 ----------------
@@ -151,9 +154,6 @@ on it.
 
 The various currently defined names are:
 
-  version             Version of FastBoot protocol supported.
-                      It should be "0.3" for this document.
-
   version-bootloader  Version string for the Bootloader.
 
   version-baseband    Version string of the Baseband Software