uart_flush_input() can now wait a bit

Calling ioctl flush too fast before actual garbage bytes arrive was useless.
It solves an issue e.g. when config asks for scanning for multiple incompatible serial devices:
One scan can mess up the reader and we've to wait & flush properly for the next driver to be able to scan correctly

libnfc/buses/uart.c

@@ -57,6 +57,22 @@
 #define LOG_GROUP    NFC_LOG_GROUP_COM
 #define LOG_CATEGORY "libnfc.bus.uart"
 
+#ifndef _WIN32
+// Needed by sleep() under Unix
+#  include <unistd.h>
+#  include <time.h>
+#  define msleep(x) do { \
+    struct timespec xsleep; \
+    xsleep.tv_sec = x / 1000; \
+    xsleep.tv_nsec = (x - xsleep.tv_sec * 1000) * 1000 * 1000; \
+    nanosleep(&xsleep, NULL); \
+  } while (0)
+#else
+// Needed by Sleep() under Windows
+#  include <winbase.h>
+#  define msleep Sleep
+#endif
+
 #  if defined(__APPLE__)
 const char *serial_ports_device_radix[] = { "tty.SLAB_USBtoUART", "tty.usbserial-", NULL };
 #  elif defined (__FreeBSD__) || defined (__OpenBSD__) || defined(__FreeBSD_kernel__)
@@ -122,8 +138,16 @@ uart_open(const char *pcPortName)
 }
 
 void
-uart_flush_input(serial_port sp)
+uart_flush_input(serial_port sp, bool wait)
 {
+  // flush commands may seem to be without effect
+  // if asked too quickly after previous event, cf comments below
+  // therefore a "wait" argument allows now to wait before flushing
+  // I believe that now the byte-eater part is not required anymore --Phil
+  if (wait) {
+    msleep(50); // 50 ms
+  }
+
   // This line seems to produce absolutely no effect on my system (GNU/Linux 2.6.35)
   tcflush(UART_DATA(sp)->fd, TCIFLUSH);
   // So, I wrote this byte-eater

libnfc/buses/uart.h

@@ -49,7 +49,7 @@ typedef void *serial_port;
 
 serial_port uart_open(const char *pcPortName);
 void    uart_close(const serial_port sp);
-void    uart_flush_input(const serial_port sp);
+void    uart_flush_input(const serial_port sp, bool wait);
 
 void    uart_set_speed(serial_port sp, const uint32_t uiPortSpeed);
 uint32_t uart_get_speed(const serial_port sp);

libnfc/drivers/acr122s.c

@@ -426,7 +426,7 @@ acr122s_scan(const nfc_context *context, nfc_connstring connstrings[], const siz
 
     if ((sp != INVALID_SERIAL_PORT) && (sp != CLAIMED_SERIAL_PORT)) {
       // We need to flush input to be sure first reply does not comes from older byte transceive
-      uart_flush_input(sp);
+      uart_flush_input(sp, true);
       uart_set_speed(sp, ACR122S_DEFAULT_SPEED);
 
       nfc_connstring connstring;
@@ -578,7 +578,7 @@ acr122s_open(const nfc_context *context, const nfc_connstring connstring)
     return NULL;
   }
 
-  uart_flush_input(sp);
+  uart_flush_input(sp, true);
   uart_set_speed(sp, ndd.speed);
 
   pnd = nfc_device_new(context, connstring);
@@ -659,7 +659,7 @@ acr122s_open(const nfc_context *context, const nfc_connstring connstring)
 static int
 acr122s_send(nfc_device *pnd, const uint8_t *buf, const size_t buf_len, int timeout)
 {
-  uart_flush_input(DRIVER_DATA(pnd)->port);
+  uart_flush_input(DRIVER_DATA(pnd)->port, false);
 
   uint8_t cmd[MAX_FRAME_SIZE];
   if (! acr122s_build_frame(pnd, cmd, sizeof(cmd), 0, 0, buf, buf_len, 1)) {

libnfc/drivers/arygon.c

@@ -113,7 +113,7 @@ arygon_scan(const nfc_context *context, nfc_connstring connstrings[], const size
 
     if ((sp != INVALID_SERIAL_PORT) && (sp != CLAIMED_SERIAL_PORT)) {
       // We need to flush input to be sure first reply does not comes from older byte transceive
-      uart_flush_input(sp);
+      uart_flush_input(sp, true);
       uart_set_speed(sp, ARYGON_DEFAULT_SPEED);
 
       nfc_connstring connstring;
@@ -266,7 +266,7 @@ arygon_open(const nfc_context *context, const nfc_connstring connstring)
   }
 
   // We need to flush input to be sure first reply does not comes from older byte transceive
-  uart_flush_input(sp);
+  uart_flush_input(sp, true);
   uart_set_speed(sp, ndd.speed);
 
   // We have a connection
@@ -340,7 +340,7 @@ arygon_tama_send(nfc_device *pnd, const uint8_t *pbtData, const size_t szData, i
 {
   int res = 0;
   // Before sending anything, we need to discard from any junk bytes
-  uart_flush_input(DRIVER_DATA(pnd)->port);
+  uart_flush_input(DRIVER_DATA(pnd)->port, false);
 
   uint8_t abtFrame[ARYGON_TX_BUFFER_LEN] = { DEV_ARYGON_PROTOCOL_TAMA, 0x00, 0x00, 0xff };     // Every packet must start with "0x32 0x00 0x00 0xff"
 

libnfc/drivers/pn532_uart.c

@@ -86,7 +86,7 @@ pn532_uart_scan(const nfc_context *context, nfc_connstring connstrings[], const
 
     if ((sp != INVALID_SERIAL_PORT) && (sp != CLAIMED_SERIAL_PORT)) {
       // We need to flush input to be sure first reply does not comes from older byte transceive
-      uart_flush_input(sp);
+      uart_flush_input(sp, true);
       // Serial port claimed but we need to check if a PN532_UART is opened.
       uart_set_speed(sp, PN532_UART_DEFAULT_SPEED);
 
@@ -237,7 +237,7 @@ pn532_uart_open(const nfc_context *context, const nfc_connstring connstring)
     return NULL;
   }
   // We need to flush input to be sure first reply does not comes from older byte transceive
-  uart_flush_input(sp);
+  uart_flush_input(sp, true);
   uart_set_speed(sp, ndd.speed);
 
   // We have a connection
@@ -315,7 +315,7 @@ pn532_uart_send(nfc_device *pnd, const uint8_t *pbtData, const size_t szData, in
 {
   int res = 0;
   // Before sending anything, we need to discard from any junk bytes
-  uart_flush_input(DRIVER_DATA(pnd)->port);
+  uart_flush_input(DRIVER_DATA(pnd)->port, false);
 
   switch (CHIP_DATA(pnd)->power_mode) {
     case LOWVBAT: {
@@ -494,7 +494,7 @@ pn532_uart_receive(nfc_device *pnd, uint8_t *pbtData, const size_t szDataLen, in
   // The PN53x command is done and we successfully received the reply
   return len;
 error:
-  uart_flush_input(DRIVER_DATA(pnd)->port);
+  uart_flush_input(DRIVER_DATA(pnd)->port, true);
   return pnd->last_error;
 }