linux-kernel - Re: [PATCH v2 07/14] USB: ch341: add support for parity, frame length, stop bits

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Date:	Sun, 03 Apr 2016 15:58:48 -0000
From:	Karl Palsson <karlp@...ak.net.au>
To:	"Grigori Goronzy" <greg@...wn.ath.cx>
Cc:	"Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
	"Johan Hovold" <johan@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linux USB Mailing List <linux-usb@...r.kernel.org>
Subject: Re: [PATCH v2 07/14] USB: ch341: add support for parity, frame length,
 stop bits


Grigori Goronzy <greg@...wn.ath.cx> wrote:
> With the new reinitialization method, configuring parity,
> different frame lengths and different stop bit settings work as
> expected on both CH340G and CH341A. This has been extensively
> tested with a logic analyzer.
> 
> Tested-by: Ryan Barber <rfb@...scraper.nu>
> Signed-off-by: Grigori Goronzy <greg@...wn.ath.cx>
> ---
>  drivers/usb/serial/ch341.c | 36 ++++++++++++++++++++++++++++++------
>  1 file changed, 30 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/usb/serial/ch341.c
> b/drivers/usb/serial/ch341.c index c001773..4d66f0f 100644
> --- a/drivers/usb/serial/ch341.c
> +++ b/drivers/usb/serial/ch341.c
> @@ -346,6 +346,7 @@ static void ch341_set_termios(struct tty_struct *tty,
>  	unsigned baud_rate;
>  	unsigned long flags;
>  	unsigned char ctrl;
> +	unsigned cflag = tty->termios.c_cflag;
>  	int r;
>  
>  	/* redundant changes may cause the chip to lose bytes */
> @@ -356,7 +357,35 @@ static void ch341_set_termios(struct tty_struct *tty,
>  
>  	priv->baud_rate = baud_rate;
>  
> -	ctrl = CH341_LCR_ENABLE_RX | CH341_LCR_ENABLE_TX | CH341_LCR_CS8;
> +	ctrl = CH341_LCR_ENABLE_RX | CH341_LCR_ENABLE_TX;
> +
> +	switch (cflag & CSIZE) {
> +	case CS5:
> +		ctrl |= CH341_LCR_CS5;
> +		break;
> +	case CS6:
> +		ctrl |= CH341_LCR_CS6;
> +		break;
> +	case CS7:
> +		ctrl |= CH341_LCR_CS7;
> +		break;
> +	case CS8:
> +	default:
> +		ctrl |= CH341_LCR_CS8;
> +		break;
> +	}
> +
> +	if (cflag & PARENB) {
> +		ctrl |= CH341_LCR_ENABLE_PAR;
> +		if ((cflag & PARODD) == 0)
> +			ctrl |= CH341_LCR_PAR_EVEN;
> +	}
> +
> +	if (cflag & CMSPAR)
> +		ctrl |= CH341_LCR_MARK_SPACE;
> +
> +	if (cflag & CSTOPB)
> +		ctrl |= CH341_LCR_STOP_BITS_2;
>  

I think this should be moved up to the PARENB check, at least,
when I was working on this. Also there's macros for some of the
flag checks: (From some code I was working on, but you can see
the mark/space is differently handled, this matched the windows
driver I was reversing usb captures from.)

if (C_PARENB(tty)) {
		*lcr |= CH341_LCR_PARITY;
		if (C_CMSPAR(tty)) {
			*lcr |= CH341_LCR_SPAR;
			if (C_PARODD(tty)) {
				dev_dbg(&port->dev, "parity = mark\n");
				*lcr &= ~CH341_LCR_EPAR;
			} else {
				dev_dbg(&port->dev, "parity = space\n");
				*lcr |= CH341_LCR_EPAR;
			}
		} else {
			*lcr &= ~CH341_LCR_SPAR;
			if (C_PARODD(tty)) {
				dev_dbg(&port->dev, "parity = odd\n");
				*lcr &= ~CH341_LCR_EPAR;
			} else {
				dev_dbg(&port->dev, "parity = even\n");
				*lcr |= CH341_LCR_EPAR;
			}
		}
	} else {
		*lcr &= ~(CH341_LCR_PARITY | CH341_LCR_SPAR | CH341_LCR_EPAR);
		dev_dbg(&port->dev, "parity = none\n");
	}



>  	if (baud_rate) {
>  		spin_lock_irqsave(&priv->lock, flags);
> @@ -373,11 +402,6 @@ static void ch341_set_termios(struct tty_struct *tty,
>  
>  	ch341_set_handshake(port->serial->dev, priv->line_control);
>  
> -	/* Unimplemented:
> -	 * (cflag & CSIZE) : data bits [5, 8]
> -	 * (cflag & PARENB) : parity {NONE, EVEN, ODD}
> -	 * (cflag & CSTOPB) : stop bits [1, 2]
> -	 */
>  }
>  
>  static void ch341_break_ctl(struct tty_struct *tty, int break_state)
> -- 
> 1.9.1
> 
> --
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