stmhal: Add ioctl to USB_VCP object, so it works with select.

This patch also enables non-blocking streams on stmhal port.

One can now make a USB-UART pass-through function:

def pass_through(usb, uart):
    while True:
        select.select([usb, uart], [], [])
        if usb.any():
            uart.write(usb.read(256))
        if uart.any():
            usb.write(uart.read(256))

pass_through(pyb.USB_VCP(), pyb.UART(1, 9600))

1 files changed, 8 insertions, 0 deletions

diff --git a/stmhal/usbd_cdc_interface.c b/stmhal/usbd_cdc_interface.c
index e9b4863f6..7f1eef5b3 100644
--- a/stmhal/usbd_cdc_interface.c
+++ b/stmhal/usbd_cdc_interface.c
@@ -402,6 +402,14 @@ void USBD_CDC_SetInterrupt(int chr, void *data) {
     user_interrupt_data = data;
 }
 
+int USBD_CDC_TxHalfEmpty(void) {
+    int32_t tx_waiting = (int32_t)UserTxBufPtrIn - (int32_t)UserTxBufPtrOut;
+    if (tx_waiting < 0) {
+        tx_waiting += APP_TX_DATA_SIZE;
+    }
+    return tx_waiting <= APP_TX_DATA_SIZE / 2;
+}
+
 // timout in milliseconds.
 // Returns number of bytes written to the device.
 int USBD_CDC_Tx(const uint8_t *buf, uint32_t len, uint32_t timeout) {