The status bit was found with USB captures of the Windows driver and
some luck. Tested on CH340G and CH341A.
Signed-off-by: Grigori Goronzy <greg@xxxxxxxxxxxx>
---
drivers/usb/serial/ch341.c | 19 ++++++++++++++++++-
1 file changed, 18 insertions(+), 1 deletion(-)
diff --git a/drivers/usb/serial/ch341.c b/drivers/usb/serial/ch341.c
index 6981e2ad..adf7d79 100644
--- a/drivers/usb/serial/ch341.c
+++ b/drivers/usb/serial/ch341.c
@@ -82,6 +82,8 @@
#define CH341_LCR_CS6 0x01
#define CH341_LCR_CS5 0x00
+#define CH341_STATUS_TXBUSY 0x01
+
static const struct usb_device_id id_table[] = {
{ USB_DEVICE(0x4348, 0x5523) },
{ USB_DEVICE(0x1a86, 0x7523) },
@@ -95,6 +97,7 @@ struct ch341_private {
unsigned baud_rate; /* set baud rate */
u8 line_control; /* set line control value RTS/DTR */
u8 line_status; /* active status of modem control inputs */
+ u8 uart_status; /* generic UART status bits */
};
static void ch341_set_termios(struct tty_struct *tty,
@@ -187,7 +190,8 @@ static int ch341_get_status(struct usb_device *dev, struct ch341_private *priv)
if (r == 2) {
r = 0;
spin_lock_irqsave(&priv->lock, flags);
- priv->line_status = (~(*buffer)) & CH341_BITS_MODEM_STAT;
+ priv->line_status = (~buffer[0]) & CH341_BITS_MODEM_STAT;
+ priv->uart_status = buffer[1];
spin_unlock_irqrestore(&priv->lock, flags);
} else {
r = -EPROTO;
@@ -198,6 +202,18 @@ out:
return r;
}
+static bool ch341_tx_empty(struct usb_serial_port *port)
+{
+ int r;
+ struct ch341_private *priv = usb_get_serial_port_data(port);
+
+ r = ch341_get_status(port->serial->dev, priv);
+ if (r < 0)
+ return true;
+
+ return !(priv->uart_status & CH341_STATUS_TXBUSY);
+}
+
/* -------------------------------------------------------------------------- */
static int ch341_configure(struct usb_device *dev, struct ch341_private *priv)
@@ -606,6 +622,7 @@ static struct usb_serial_driver ch341_device = {
.carrier_raised = ch341_carrier_raised,
.close = ch341_close,
.set_termios = ch341_set_termios,
+ .tx_empty = ch341_tx_empty,
.break_ctl = ch341_break_ctl,
.tiocmget = ch341_tiocmget,
.tiocmset = ch341_tiocmset,
--
1.9.1
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