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Date:	Sun, 30 Mar 2008 14:09:48 +0200
From:	postmaster@...-ginkel.eu
To:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ptmx: adding handshake support

This weekend I upgraded my kernel to 2.6.22.5 and tried my patch.
Unfortunately pty.c seems to be a slightly different, so generated a new
patch:

  Signed-off-by: Sander van Ginkel <sander@...-ginkel.eu>

===================================================================
--- linux-2.6.22.5.orig/drivers/char/pty.c	2007-08-23 01:23:54.000000000 +0200
+++ linux-2.6.22.5.new/drivers/char/pty.c	2008-03-23 15:25:24.000000000 +0100
@@ -7,6 +7,8 @@
   *    -- C. Scott Ananian <cananian@...mni.princeton.edu>, 14-Jan-1998
   *  Added TTY_DO_WRITE_WAKEUP to enable n_tty to send POLL_OUT to
   *      waiting writers -- Sapan Bhatia <sapan@...ewars.org>
+ *  Added support for MCR/MSR, used for serial over ethernet
+ *    -- Sander van Ginkel <sander@...-ginkel.eu>
   *
   *
   */
@@ -29,6 +31,16 @@
  #include <linux/bitops.h>
  #include <linux/devpts_fs.h>

+struct pty_mcrmsr {
+
+	struct semaphore        sem;            /* locks this structure */
+
+	/* for tiocmget and tiocmset functions */
+
+	int                     msr;            /* MSR shadow */
+	int                     mcr;            /* MCR shadow */
+};
+
  /* These are global because they are accessed in tty_io.c */
  #ifdef CONFIG_UNIX98_PTYS
  struct tty_driver *ptm_driver;
@@ -196,6 +208,7 @@

  static int pty_open(struct tty_struct *tty, struct file * filp)
  {
+        struct pty_mcrmsr *mcrmsr;
  	int	retval = -ENODEV;

  	if (!tty || !tty->link)
@@ -213,10 +226,90 @@
  	set_bit(TTY_THROTTLED, &tty->flags);
  	set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
  	retval = 0;
+
+	/* initialize the pointer in case something fails */
+
+	tty->driver_data = NULL;
+	tty->link->driver_data = NULL;
+
+	/* first time accessing this device, let's create it */
+
+	mcrmsr = kmalloc(sizeof(*mcrmsr), GFP_KERNEL);
+
+	init_MUTEX(&mcrmsr->sem);
+
+	if (mcrmsr != NULL) {
+		down(&mcrmsr->sem);
+
+		/* save our structure within the tty structure */
+
+		mcrmsr->mcr=0;
+		mcrmsr->msr=0;
+
+		tty->driver_data = mcrmsr;
+		tty->link->driver_data = mcrmsr;
+
+		up(&mcrmsr->sem);
+
+	}
+
  out:
  	return retval;
  }

+static int pty_tiocmget(struct tty_struct *tty, struct file *file)
+{
+	struct pty_mcrmsr *mcrmsr = tty->driver_data;
+	unsigned int result = 0;
+	unsigned int msr=0;
+	unsigned int mcr=0;
+
+	if (tty->driver_data != NULL) {
+		msr = mcrmsr->msr;
+		mcr = mcrmsr->mcr;
+	}
+
+	result = ((mcr & 0x01)  ? TIOCM_DTR  : 0) |  /* DTR is set */
+		((mcr & 0x02)  ? TIOCM_RTS  : 0) |  /* RTS is set */
+		((mcr & 0x04)  ? TIOCM_LOOP : 0) |  /* LOOP is set */
+		((msr & 0x08)  ? TIOCM_CTS  : 0) |  /* CTS is set */
+		((msr & 0x10)  ? TIOCM_CAR  : 0) |  /* Carrier detect is set*/
+		((msr & 0x20)  ? TIOCM_RI   : 0) |  /* Ring Indicator is set */
+		((msr & 0x40)  ? TIOCM_DSR  : 0);   /* DSR is set */
+
+	return result;
+}
+
+static int pty_tiocmset(struct tty_struct *tty, struct file  
*file,unsigned int set, unsigned int clear)
+{
+	struct pty_mcrmsr *mcrmsr = tty->driver_data;
+	unsigned int mcr=0;
+
+	if (tty->driver_data != NULL)
+		mcr = mcrmsr->mcr;
+
+	if (set & TIOCM_DTR)
+		mcr |= 0x01;
+	if (set & TIOCM_RTS)
+		mcr |= 0x02;
+	if (set & TIOCM_LOOP)
+		mcr |= 0x04;
+
+	if (clear & TIOCM_DTR)
+		mcr &= ~0x01;
+	if (clear & TIOCM_RTS)
+		mcr &= ~0x02;
+	if (clear & TIOCM_LOOP)
+		mcr &= ~0x04;
+
+	/* set the new MCR value in the device */
+
+	if (tty->driver_data != NULL)
+		mcrmsr->mcr=mcr;
+
+	return 0;
+}
+
  static void pty_set_termios(struct tty_struct *tty, struct ktermios  
*old_termios)
  {
          tty->termios->c_cflag &= ~(CSIZE | PARENB);
@@ -232,6 +325,8 @@
  	.chars_in_buffer = pty_chars_in_buffer,
  	.unthrottle = pty_unthrottle,
  	.set_termios = pty_set_termios,
+	.tiocmget = pty_tiocmget,
+	.tiocmset = pty_tiocmset,
  };

  /* Traditional BSD devices */
@@ -338,11 +433,44 @@
  static int pty_unix98_ioctl(struct tty_struct *tty, struct file *file,
  			    unsigned int cmd, unsigned long arg)
  {
+	unsigned int value;
+	struct pty_mcrmsr *mcrmsr = tty->driver_data;
+	unsigned int msr=0;
+	unsigned int mcr=0;
+
  	switch (cmd) {
  	case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
  		return pty_set_lock(tty, (int __user *)arg);
  	case TIOCGPTN: /* Get PT Number */
  		return put_user(tty->index, (unsigned int __user *)arg);
+
+	case 0x5426: /* Set all of the handshake line, even the normally  
read only */
+		{
+		if (copy_from_user(&value,(unsigned int *)arg,sizeof(unsigned int)))
+			return -EFAULT;
+
+		if (value & 0x0002) /* DTR set */
+			mcr|=0x01;
+		if (value & 0x0004) /* RTS set */
+			mcr|=0x02;
+		if (value & 0x8000) /* LOOP set */
+			mcr|=0x04;
+		if (value & 0x0020) /* CTS set */
+			msr|=0x08;
+		if (value & 0x0040) /* DCD set */
+			msr|=0x10;
+		if (value & 0x0080) /* RI set */
+			msr|=0x20;
+		if (value & 0x0100) /* DSR set */
+			msr|=0x40;
+
+		if (tty->driver_data != NULL)
+			{
+			mcrmsr->msr=msr;
+			mcrmsr->mcr=mcr;
+			}
+		return 0;
+		}
  	}

  	return -ENOIOCTLCMD;


Quoting sander van ginkel <sander@...-ginkel.eu>:

> For serial over ethernet communication, /dev/ptmx will be used to
> create a virtual device.
> Due to the lack of a modem status register and a modem control register
> in the ptmx driver,
> it won't be possible to transfer handshake signaling.
>
> I wrote this patch to add these registers to the ptmx driver.
> The modem status register, which controls CD,CTS,DSR,RI is normally
> read-only. To be able to
> pass these signals from the remote port to the local ptmx device, I've
> added an IOCTL routine.
> The result of a remote TIOCMGET IOCTL call , can be passed directly
> through this IOCTL routine.
> The IOCTL value I used for this is, 0x5426 which was formerly known as
> TIOCTTYGSTRUCT.
>
> I've tested this patch at an 2.6.16.27 kernel.
>
> Suggestions and/or other test results are welcome.
>
> Sander
>
>
> Signed-off-by: Sander van Ginkel <sander@...-ginkel.eu>
>
> ===================================================================
> --- drivers/char/pty.c	2008-03-03 20:02:09.000000000 +0100
> +++ drivers/char/pty-new.c	2008-03-02 21:55:53.000000000 +0100
> @@ -7,6 +7,8 @@
>   *    -- C. Scott Ananian <cananian@...mni.princeton.edu>, 14-Jan-1998
>   *  Added TTY_DO_WRITE_WAKEUP to enable n_tty to send POLL_OUT to
>   *      waiting writers -- Sapan Bhatia <sapan@...ewars.org>
> + *  Added support for MCR/MSR, used for serial over ethernet
> + *    -- Sander van Ginkel <sander@...-ginkel.eu>
>   *
>   *
>   */
> @@ -32,6 +34,16 @@
>  #include <linux/bitops.h>
>  #include <linux/devpts_fs.h>
>
> +struct pty_mcrmsr {
> +
> +	struct semaphore        sem;            /* locks this structure */
> +
> +	/* for tiocmget and tiocmset functions */
> +
> +	int                     msr;            /* MSR shadow */
> +	int                     mcr;            /* MCR shadow */
> +};
> +
>  /* These are global because they are accessed in tty_io.c */
>  #ifdef CONFIG_UNIX98_PTYS
>  struct tty_driver *ptm_driver;
> @@ -199,6 +211,7 @@
>
>  static int pty_open(struct tty_struct *tty, struct file * filp)
>  {
> +        struct pty_mcrmsr *mcrmsr;
>  	int	retval = -ENODEV;
>
>  	if (!tty || !tty->link)
> @@ -216,10 +229,90 @@
>  	set_bit(TTY_THROTTLED, &tty->flags);
>  	set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
>  	retval = 0;
> +
> +	/* initialize the pointer in case something fails */
> +
> +	tty->driver_data = NULL;
> +	tty->link->driver_data = NULL;
> +
> +	/* first time accessing this device, let's create it */
> +
> +	mcrmsr = kmalloc(sizeof(*mcrmsr), GFP_KERNEL);
> +
> +	init_MUTEX(&mcrmsr->sem);
> +
> +	if (mcrmsr != NULL) {
> +		down(&mcrmsr->sem);
> +
> +		/* save our structure within the tty structure */
> +
> +		mcrmsr->mcr=0;
> +		mcrmsr->msr=0;
> +
> +		tty->driver_data = mcrmsr;
> +		tty->link->driver_data = mcrmsr;
> +
> +		up(&mcrmsr->sem);
> +
> +	}
> +
>  out:
>  	return retval;
>  }
>
> +static int pty_tiocmget(struct tty_struct *tty, struct file *file)
> +{
> +	struct pty_mcrmsr *mcrmsr = tty->driver_data;
> +	unsigned int result = 0;
> +	unsigned int msr=0;
> +	unsigned int mcr=0;
> +
> +	if (tty->driver_data != NULL) {
> +		msr = mcrmsr->msr;
> +		mcr = mcrmsr->mcr;
> +	}
> +
> +	result = ((mcr & 0x01)  ? TIOCM_DTR  : 0) |  /* DTR is set */
> +		((mcr & 0x02)  ? TIOCM_RTS  : 0) |  /* RTS is set */
> +		((mcr & 0x04)  ? TIOCM_LOOP : 0) |  /* LOOP is set */
> +		((msr & 0x08)  ? TIOCM_CTS  : 0) |  /* CTS is set */
> +		((msr & 0x10)  ? TIOCM_CAR  : 0) |  /* Carrier detect is set*/
> +		((msr & 0x20)  ? TIOCM_RI   : 0) |  /* Ring Indicator is set */
> +		((msr & 0x40)  ? TIOCM_DSR  : 0);   /* DSR is set */
> +
> +	return result;
> +}
> +
> +static int pty_tiocmset(struct tty_struct *tty, struct file
> *file,unsigned int set, unsigned int clear)
> +{
> +	struct pty_mcrmsr *mcrmsr = tty->driver_data;
> +	unsigned int mcr=0;
> +
> +	if (tty->driver_data != NULL)
> +		mcr = mcrmsr->mcr;
> +
> +	if (set & TIOCM_DTR)
> +		mcr |= 0x01;
> +	if (set & TIOCM_RTS)
> +		mcr |= 0x02;
> +	if (set & TIOCM_LOOP)
> +		mcr |= 0x04;
> +
> +	if (clear & TIOCM_DTR)
> +		mcr &= ~0x01;
> +	if (clear & TIOCM_RTS)
> +		mcr &= ~0x02;
> +	if (clear & TIOCM_LOOP)
> +		mcr &= ~0x04;
> +
> +	/* set the new MCR value in the device */
> +
> +	if (tty->driver_data != NULL)
> +		mcrmsr->mcr=mcr;
> +
> +	return 0;
> +}
> +
>  static void pty_set_termios(struct tty_struct *tty, struct termios
> *old_termios)
>  {
>          tty->termios->c_cflag &= ~(CSIZE | PARENB);
> @@ -235,6 +328,8 @@
>  	.chars_in_buffer = pty_chars_in_buffer,
>  	.unthrottle = pty_unthrottle,
>  	.set_termios = pty_set_termios,
> +	.tiocmget = pty_tiocmget,
> +	.tiocmset = pty_tiocmset,
>  };
>
>  /* Traditional BSD devices */
> @@ -339,11 +434,44 @@
>  static int pty_unix98_ioctl(struct tty_struct *tty, struct file *file,
>  			    unsigned int cmd, unsigned long arg)
>  {
> +	unsigned int value;
> +	struct pty_mcrmsr *mcrmsr = tty->driver_data;
> +	unsigned int msr=0;
> +	unsigned int mcr=0;
> +
>  	switch (cmd) {
>  	case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
>  		return pty_set_lock(tty, (int __user *)arg);
>  	case TIOCGPTN: /* Get PT Number */
>  		return put_user(tty->index, (unsigned int __user *)arg);
> +
> +	case 0x5426: /* Set all of the handshake line, even the normally read
> only */
> +		{
> +		if (copy_from_user(&value,(unsigned int *)arg,sizeof(unsigned int)))
> +			return -EFAULT;
> +
> +		if (value & 0x0002) /* DTR set */
> +			mcr|=0x01;
> +		if (value & 0x0004) /* RTS set */
> +			mcr|=0x02;
> +		if (value & 0x8000) /* LOOP set */
> +			mcr|=0x04;
> +		if (value & 0x0020) /* CTS set */
> +			msr|=0x08;
> +		if (value & 0x0040) /* DCD set */
> +			msr|=0x10;
> +		if (value & 0x0080) /* RI set */
> +			msr|=0x20;
> +		if (value & 0x0100) /* DSR set */
> +			msr|=0x40;
> +
> +		if (tty->driver_data != NULL)
> +			{
> +			mcrmsr->msr=msr;
> +			mcrmsr->mcr=mcr;
> +			}
> +		return 0;
> +		}
>  	}
>
>  	return -ENOIOCTLCMD;



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