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[PATCH v2 14/14] USB: ch341: implement tx_empty callback

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  [PATCH v2 14/14] USB: ch341: implement tx_empty callback Grigori Goronzy <greg@chown.ath.cx> - 2016-04-02 19:20 +0200
    Re: [PATCH v2 14/14] USB: ch341: implement tx_empty callback Karl Palsson <karlp@tweak.net.au> - 2016-04-03 18:10 +0200
      Re: [PATCH v2 14/14] USB: ch341: implement tx_empty callback Grigori Goronzy <greg@chown.ath.cx> - 2016-04-06 20:10 +0200

#1370013 — [PATCH v2 14/14] USB: ch341: implement tx_empty callback

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@chown.ath.cx>
---
 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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#1370248

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Grigori Goronzy <greg@chown.ath.cx> wrote:
> The status bit was found with USB captures of the Windows
> driver and some luck. Tested on CH340G and CH341A.

By my reversing, bit 0x4, is "multiple status changes since last
interrupt"

> 
> Signed-off-by: Grigori Goronzy <greg@chown.ath.cx>
> ---
>  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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#1372712

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On 04/03/2016 06:03 PM, Karl Palsson wrote:
> 
> Grigori Goronzy <greg@chown.ath.cx> wrote:
>> The status bit was found with USB captures of the Windows
>> driver and some luck. Tested on CH340G and CH341A.
> 
> By my reversing, bit 0x4, is "multiple status changes since last
> interrupt"
>

Thanks, I can add the definition.  However, I wonder what this is
actually good for.  We don't actually need this to see that there are
multiple status changes.  We can just look at the different bits.

Grigori

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