Flush keyboard at start of screens which take keyboard input

BUG=chrome-os-partner:11887
TEST=manual

Boot with dev mode on.  Boots normally.

Boot with dev mode on, hammering on ENTER key as soon as you release power.
Dev mode screen is shown.
Keep hammering.  Dev screen will stay up as long as you do this.
Wait >2 sec.
Press ENTER.  System reboots to TONORM screen.

Change-Id: I18e35b23c18a65637a84d3d1964b291e0cb5e8c5
Signed-off-by: Randall Spangler <rspangler@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/28995
Reviewed-by: Tom Wai-Hong Tam <waihong@chromium.org>

1 files changed, 51 insertions, 1 deletions

diff --git a/firmware/lib/vboot_api_kernel.c b/firmware/lib/vboot_api_kernel.c
index 9c5dd7f4..9ac3f08d 100644
--- a/firmware/lib/vboot_api_kernel.c
+++ b/firmware/lib/vboot_api_kernel.c
@@ -35,7 +35,6 @@ static void VbSetRecoveryRequest(uint32_t recovery_request) {
 }
 
 
-
 /* Attempt loading a kernel from the specified type(s) of disks.  If
  * successful, sets p->disk_handle to the disk for the kernel and returns
  * VBERROR_SUCCESS.
@@ -106,6 +105,34 @@ uint32_t VbTryLoadKernel(VbCommonParams* cparams, LoadKernelParams* p,
   return retval;
 }
 
+/* Flush the keyboard buffer. */
+static VbError_t FlushKeyboard(void) {
+
+  int loops = 0;
+
+  /* Wait half a second to see if any keys are pressed.  If keys are
+   * auto-repeating, they'll repeat by then. */
+  VbExSleepMs(500);
+
+  /* If no keys are pressed, no need for any subsequent delay. */
+  if (!VbExKeyboardRead())
+    return VBERROR_SUCCESS;
+
+  /* Otherwise, wait 2 sec after the last key is pressed. */
+  VBDEBUG(("Keys held down at start of screen; flushing...\n"));
+  do {
+    if (VbExIsShutdownRequested())
+      return VBERROR_SHUTDOWN_REQUESTED;
+
+    VbExSleepMs(250);
+    loops++;
+    if (VbExKeyboardRead())
+      loops = 0;
+  } while (loops < 8);
+  VBDEBUG(("...done flushing.\n"));
+
+  return VBERROR_SUCCESS;
+}
 
 /* Handle a normal boot. */
 VbError_t VbBootNormal(VbCommonParams* cparams, LoadKernelParams* p) {
@@ -131,6 +158,10 @@ VbError_t VbBootDeveloper(VbCommonParams* cparams, LoadKernelParams* p) {
   /* Show the dev mode warning screen */
   VbDisplayScreen(cparams, VB_SCREEN_DEVELOPER_WARNING, 0, &vnc);
 
+  /* Flush any pending keystrokes */
+  if (FlushKeyboard() == VBERROR_SHUTDOWN_REQUESTED)
+    return VBERROR_SHUTDOWN_REQUESTED;
+
   /* Get audio/delay context */
   audio = VbAudioOpen(cparams);
 
@@ -219,6 +250,10 @@ static VbError_t VbConfirmChangeDevMode(VbCommonParams* cparams, int to_dev) {
   VbDisplayScreen(cparams, (to_dev ? VB_SCREEN_RECOVERY_TO_DEV
                             : VB_SCREEN_RECOVERY_TO_NORM), 0, &vnc);
 
+  /* Flush any pending keystrokes */
+  if (FlushKeyboard() == VBERROR_SHUTDOWN_REQUESTED)
+    return VBERROR_SHUTDOWN_REQUESTED;
+
   /* Await further instructions */
   while (1) {
     if (VbExIsShutdownRequested())
@@ -253,6 +288,7 @@ VbError_t VbBootRecovery(VbCommonParams* cparams, LoadKernelParams* p) {
   VbSharedDataHeader* shared = (VbSharedDataHeader*)cparams->shared_data_blob;
   uint32_t retval;
   uint32_t key;
+  int kb_flushed = 0;
   int i;
 
   VBDEBUG(("VbBootRecovery() start\n"));
@@ -282,6 +318,13 @@ VbError_t VbBootRecovery(VbCommonParams* cparams, LoadKernelParams* p) {
 
       VbDisplayScreen(cparams, VB_SCREEN_RECOVERY_REMOVE, 0, &vnc);
 
+      /* Flush any pending keystrokes */
+      if (!kb_flushed) {
+        if (FlushKeyboard() == VBERROR_SHUTDOWN_REQUESTED)
+          return VBERROR_SHUTDOWN_REQUESTED;
+        kb_flushed = 1;
+      }
+
       /* Scan keyboard more frequently than media, since x86 platforms
        * don't like to scan USB too rapidly. */
       for (i = 0; i < 4; i++) {
@@ -322,6 +365,13 @@ VbError_t VbBootRecovery(VbCommonParams* cparams, LoadKernelParams* p) {
                     VB_SCREEN_RECOVERY_INSERT : VB_SCREEN_RECOVERY_NO_GOOD,
                     0, &vnc);
 
+    /* Flush any pending keystrokes */
+    if (!kb_flushed) {
+      if (FlushKeyboard() == VBERROR_SHUTDOWN_REQUESTED)
+        return VBERROR_SHUTDOWN_REQUESTED;
+      kb_flushed = 1;
+    }
+
     /* Scan keyboard more frequently than media, since x86 platforms don't like
      * to scan USB too rapidly. */
     for (i = 0; i < 4; i++) {