fix(legacy): cleanup of undesired states where USB processing should not happen

legacy/common.c

@@ -19,6 +19,7 @@
 
 #include "common.h"
 #include <stdio.h>
+#include <unistd.h>
 #include "bitmaps.h"
 #include "firmware/usb.h"
 #include "hmac_drbg.h"
@@ -83,7 +84,17 @@ void __assert_func(const char *file, int line, const char *func,
 }
 #endif
 
-void hal_delay(uint32_t ms) { usbSleep(ms); }
+void hal_delay(uint32_t ms) {
+#if EMULATOR
+  usleep(ms * 1000);
+#else
+  uint32_t start = timer_ms();
+
+  while ((timer_ms() - start) < ms) {
+    asm("nop");
+  }
+#endif
+}
 
 void drbg_init() {
   uint8_t entropy[48] = {0};

legacy/firmware/.changelog.d/2107.fixed

@@ -0,0 +1 @@
+Fix legacy technical debt in USB handling (readability and FSM unwanted states).

legacy/firmware/config.c

@@ -564,7 +564,7 @@ void config_setHomescreen(const uint8_t *data, uint32_t size) {
 }
 
 static void get_root_node_callback(uint32_t iter, uint32_t total) {
-  usbSleep(1);
+  waitAndProcessUSBRequests(1);
   layoutProgress(_("Waking up"), 1000 * iter / total);
 }
 

legacy/firmware/protect.c

@@ -64,7 +64,7 @@ bool protectButton(ButtonRequestType type, bool confirm_only) {
 
     // button acked - check buttons
     if (acked) {
-      usbSleep(5);
+      waitAndProcessUSBRequests(5);
       buttonUpdate();
       if (button.YesUp) {
         result = true;

legacy/firmware/recovery.c

@@ -421,7 +421,7 @@ static void recovery_digit(const char digit) {
     oledInvert(x + 1, y, x + 62, y + 9);
     oledRefresh();
     usbTiny(1);
-    usbSleep(250);
+    waitAndProcessUSBRequests(250);
     usbTiny(0);
 
     /* index of the chosen word */

legacy/firmware/trezor.c

@@ -77,13 +77,13 @@ void check_lock_screen(void) {
     // wait until NoButton is released
     usbTiny(1);
     do {
-      usbSleep(5);
+      waitAndProcessUSBRequests(5);
       buttonUpdate();
     } while (!button.NoUp);
 
     // wait for confirmation/cancellation of the dialog
     do {
-      usbSleep(5);
+      waitAndProcessUSBRequests(5);
       buttonUpdate();
     } while (!button.YesUp && !button.NoUp);
     usbTiny(0);
@@ -180,7 +180,7 @@ int main(void) {
   usbInit();
   for (;;) {
 #if EMULATOR
-    usbSleep(10);
+    waitAndProcessUSBRequests(10);
 #else
     usbPoll();
 #endif

legacy/firmware/udp.c

@@ -18,6 +18,7 @@
  */
 
 #include <stdint.h>
+#include <unistd.h>
 
 #include "usb.h"
 
@@ -35,7 +36,7 @@ void usbInit(void) { emulatorSocketInit(); }
 #define _ISDBG ('n')
 #endif
 
-void usbSleep(uint32_t millis) {
+void waitAndProcessUSBRequests(uint32_t millis) {
   emulatorPoll();
 
   static uint8_t buffer[USB_PACKET_SIZE];
@@ -63,7 +64,7 @@ void usbSleep(uint32_t millis) {
 #endif
 }
 
-void usbPoll(void) { usbSleep(0); }
+void usbPoll(void) { waitAndProcessUSBRequests(0); }
 
 char usbTiny(char set) {
   char old = tiny;
@@ -71,4 +72,10 @@ char usbTiny(char set) {
   return old;
 }
 
-void usbFlush(uint32_t millis) { usbSleep(millis); }
+void usbFlush(uint32_t millis) {
+  const uint8_t *data;
+  while ((data = msg_out_data()) != NULL) {
+    emulatorSocketWrite(0, data, USB_PACKET_SIZE);
+  }
+  usleep(millis * 1000);
+}

legacy/firmware/usb.c

@@ -448,7 +448,7 @@ char usbTiny(char set) {
   return old;
 }
 
-void usbSleep(uint32_t millis) {
+void waitAndProcessUSBRequests(uint32_t millis) {
   uint32_t start = timer_ms();
 
   while ((timer_ms() - start) < millis) {

legacy/firmware/usb.h

@@ -25,8 +25,34 @@
 void usbInit(void);
 void usbPoll(void);
 void usbReconnect(void);
+
+/*
+ * Setting this value to 1 will limit the protobuf messages `usbPoll` and
+ * `waitAndProcessUSBRequests` can handle to a few defined in `msg_read_tiny`.
+ *
+ * Also affects U2F and DebugLink messages.
+ *
+ * Setting to 1 is meant to prevent infinite recursion when you need to read a
+ * message while being called from FSM.
+ *
+ * Setting to 0 allows processing all messages.
+ */
 char usbTiny(char set);
-void usbSleep(uint32_t millis);
+
+/*
+ * This will wait given number of milliseconds for arrival of protobuf message.
+ * If it arrives, it will service it before returning.
+ *
+ * If you call this function from any function that is called from FSM,
+ * you must use `usbTiny(1)` before and `usbTiny(oldTinyValue)` or `usbTiny(0)`
+ * after, otherwise there is possibility of stack exhaustion.
+ */
+void waitAndProcessUSBRequests(uint32_t millis);
+
+/*
+ * Flush out any messages still in USB bus FIFO while waiting given number
+ * of milliseconds. Any incoming USB protobuf messages are not serviced.
+ */
 void usbFlush(uint32_t millis);
 
 #endif