[PATCHv3 1/4] tty: n_gsm: remove obsolete mknod doc example

[PATCHv3 1/4] tty: n_gsm: remove obsolete mknod doc example

[Martin Hundebøll]

The n_gsm driver handles registration of /dev/gsmttyX nodes, so there's
no need to do mknod manually.

Signed-off-by: Martin Hundebøll <martin@geanix.com>
---
 Documentation/serial/n_gsm.rst | 14 ++------------
 1 file changed, 2 insertions(+), 12 deletions(-)

diff --git a/Documentation/serial/n_gsm.rst b/Documentation/serial/n_gsm.rst
index f3ad9fd26408..4f37198423f7 100644
--- a/Documentation/serial/n_gsm.rst
+++ b/Documentation/serial/n_gsm.rst
@@ -63,24 +63,14 @@ Major parts of the initialization program :
 	daemon(0,0);
 	pause();
 
-4. create the devices corresponding to the "virtual" serial ports (take care,
-   each modem has its configuration and some DLC have dedicated functions,
-   for example GPS), starting with minor 1 (DLC0 is reserved for the management
-   of the mux)::
-
-     MAJOR=`cat /proc/devices |grep gsmtty | awk '{print $1}`
-     for i in `seq 1 4`; do
-	mknod /dev/ttygsm$i c $MAJOR $i
-     done
-
-5. use these devices as plain serial ports.
+4. use these devices as plain serial ports.
 
    for example, it's possible:
 
    - and to use gnokii to send / receive SMS on ttygsm1
    - to use ppp to establish a datalink on ttygsm2
 
-6. first close all virtual ports before closing the physical port.
+5. first close all virtual ports before closing the physical port.
 
    Note that after closing the physical port the modem is still in multiplexing
    mode. This may prevent a successful re-opening of the port later. To avoid
-- 
2.22.0

[PATCHv3 2/4] tty: n_gsm: update doc example to use header for N_GSM0710 define

[Martin Hundebøll]

There is no reason to gues the line discipline number when it is
available from tty.h

Signed-off-by: Martin Hundebøll <martin@geanix.com>
---
 Documentation/serial/n_gsm.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Documentation/serial/n_gsm.rst b/Documentation/serial/n_gsm.rst
index 4f37198423f7..0ba731ab00b2 100644
--- a/Documentation/serial/n_gsm.rst
+++ b/Documentation/serial/n_gsm.rst
@@ -23,7 +23,7 @@ Major parts of the initialization program :
 (a good starting point is util-linux-ng/sys-utils/ldattach.c)::
 
   #include <linux/gsmmux.h>
-  #define N_GSM0710	21	/* GSM 0710 Mux */
+  #include <linux/tty.h>
   #define DEFAULT_SPEED	B115200
   #define SERIAL_PORT	/dev/ttyS0
 
-- 
2.22.0

[PATCHv3 3/4] tty: n_gsm: add helpers to convert mux-num to/from tty-base

[Martin Hundebøll]

Make it obvious how the gsm mux number relates to the virtual tty lines
by using helper functions instead of shifting 6 bits.

Signed-off-by: Martin Hundebøll <martin@geanix.com>
---

Changes since v2:
 * use unsigned integers in both helper functions

 drivers/tty/n_gsm.c | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index c4e16b31f9ab..a60be591f1fc 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -2171,6 +2171,16 @@ static inline void mux_put(struct gsm_mux *gsm)
 	kref_put(&gsm->ref, gsm_free_muxr);
 }
 
+static inline unsigned int mux_num_to_base(struct gsm_mux *gsm)
+{
+	return gsm->num * NUM_DLCI;
+}
+
+static inline unsigned int mux_line_to_num(unsigned int line)
+{
+	return line / NUM_DLCI;
+}
+
 /**
  *	gsm_alloc_mux		-	allocate a mux
  *
@@ -2351,7 +2361,8 @@ static int gsmld_output(struct gsm_mux *gsm, u8 *data, int len)
 
 static int gsmld_attach_gsm(struct tty_struct *tty, struct gsm_mux *gsm)
 {
-	int ret, i, base;
+	unsigned int base;
+	int ret, i;
 
 	gsm->tty = tty_kref_get(tty);
 	gsm->output = gsmld_output;
@@ -2361,7 +2372,7 @@ static int gsmld_attach_gsm(struct tty_struct *tty, struct gsm_mux *gsm)
 	else {
 		/* Don't register device 0 - this is the control channel and not
 		   a usable tty interface */
-		base = gsm->num << 6; /* Base for this MUX */
+		base = mux_num_to_base(gsm); /* Base for this MUX */
 		for (i = 1; i < NUM_DLCI; i++)
 			tty_register_device(gsm_tty_driver, base + i, NULL);
 	}
@@ -2379,8 +2390,8 @@ static int gsmld_attach_gsm(struct tty_struct *tty, struct gsm_mux *gsm)
 
 static void gsmld_detach_gsm(struct tty_struct *tty, struct gsm_mux *gsm)
 {
+	unsigned int base = mux_num_to_base(gsm); /* Base for this MUX */
 	int i;
-	int base = gsm->num << 6; /* Base for this MUX */
 
 	WARN_ON(tty != gsm->tty);
 	for (i = 1; i < NUM_DLCI; i++)
@@ -2908,7 +2919,7 @@ static int gsmtty_install(struct tty_driver *driver, struct tty_struct *tty)
 	struct gsm_mux *gsm;
 	struct gsm_dlci *dlci;
 	unsigned int line = tty->index;
-	unsigned int mux = line >> 6;
+	unsigned int mux = mux_line_to_num(line);
 	bool alloc = false;
 	int ret;
 
-- 
2.22.0

[PATCHv3 4/4] tty: n_gsm: add ioctl to map serial device to mux'ed tty

[Martin Hundebøll]

Guessing the first tty for a gsm0710 multiplexed serial device is not
currently possible, which makes it racy to use with multiple modems.

Add a way to map the physical serial tty to its related mux devices
using an ioctl.

Signed-off-by: Martin Hundebøll <martin@geanix.com>
---

Changes since v2:
 * rename IOCTL from GSMIOC_GETBASE to GSMIOC_GETFIRST
 * return first usable line instead of private control line
 * return uint32_t instead of int

Changes since v1:
 * use put_user() instead of copy_to_user()
 * add missing opening quote

 Documentation/serial/n_gsm.rst | 11 +++++++++--
 drivers/tty/n_gsm.c            |  4 ++++
 include/uapi/linux/gsmmux.h    |  2 ++
 3 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/Documentation/serial/n_gsm.rst b/Documentation/serial/n_gsm.rst
index 0ba731ab00b2..286e7ff4d2d9 100644
--- a/Documentation/serial/n_gsm.rst
+++ b/Documentation/serial/n_gsm.rst
@@ -18,10 +18,13 @@ How to use it
 2. switch the serial line to using the n_gsm line discipline by using
    TIOCSETD ioctl,
 3. configure the mux using GSMIOC_GETCONF / GSMIOC_SETCONF ioctl,
+4. obtain base gsmtty number for the used serial port,
 
 Major parts of the initialization program :
 (a good starting point is util-linux-ng/sys-utils/ldattach.c)::
 
+  #include <stdio.h>
+  #include <stdint.h>
   #include <linux/gsmmux.h>
   #include <linux/tty.h>
   #define DEFAULT_SPEED	B115200
@@ -30,6 +33,7 @@ Major parts of the initialization program :
 	int ldisc = N_GSM0710;
 	struct gsm_config c;
 	struct termios configuration;
+	uint32_t first;
 
 	/* open the serial port connected to the modem */
 	fd = open(SERIAL_PORT, O_RDWR | O_NOCTTY | O_NDELAY);
@@ -58,19 +62,22 @@ Major parts of the initialization program :
 	c.mtu = 127;
 	/* set the new configuration */
 	ioctl(fd, GSMIOC_SETCONF, &c);
+	/* get first gsmtty device node */
+	ioctl(fd, GSMIOC_GETFIRST, &first);
+	printf("first muxed line: /dev/gsmtty%i\n", first);
 
 	/* and wait for ever to keep the line discipline enabled */
 	daemon(0,0);
 	pause();
 
-4. use these devices as plain serial ports.
+5. use these devices as plain serial ports.
 
    for example, it's possible:
 
    - and to use gnokii to send / receive SMS on ttygsm1
    - to use ppp to establish a datalink on ttygsm2
 
-5. first close all virtual ports before closing the physical port.
+6. first close all virtual ports before closing the physical port.
 
    Note that after closing the physical port the modem is still in multiplexing
    mode. This may prevent a successful re-opening of the port later. To avoid
diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index a60be591f1fc..dac98f3ead3d 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -2613,6 +2613,7 @@ static int gsmld_ioctl(struct tty_struct *tty, struct file *file,
 {
 	struct gsm_config c;
 	struct gsm_mux *gsm = tty->disc_data;
+	unsigned int base;
 
 	switch (cmd) {
 	case GSMIOC_GETCONF:
@@ -2624,6 +2625,9 @@ static int gsmld_ioctl(struct tty_struct *tty, struct file *file,
 		if (copy_from_user(&c, (void *)arg, sizeof(c)))
 			return -EFAULT;
 		return gsm_config(gsm, &c);
+	case GSMIOC_GETFIRST:
+		base = mux_num_to_base(gsm);
+		return put_user(base + 1, (uint32_t __user *)arg);
 	default:
 		return n_tty_ioctl_helper(tty, file, cmd, arg);
 	}
diff --git a/include/uapi/linux/gsmmux.h b/include/uapi/linux/gsmmux.h
index 101d3c469acb..e292869245dc 100644
--- a/include/uapi/linux/gsmmux.h
+++ b/include/uapi/linux/gsmmux.h
@@ -37,5 +37,7 @@ struct gsm_netconfig {
 #define GSMIOC_ENABLE_NET      _IOW('G', 2, struct gsm_netconfig)
 #define GSMIOC_DISABLE_NET     _IO('G', 3)
 
+/* get the base tty number for a configured gsmmux tty */
+#define GSMIOC_GETFIRST		_IOR('G', 4, uint32_t)
 
 #endif
-- 
2.22.0

Re: [PATCHv3 4/4] tty: n_gsm: add ioctl to map serial device to mux'ed tty

[Greg Kroah-Hartman]

On Wed, Jul 10, 2019 at 09:26:56PM +0200, Martin Hundebøll wrote:
> Guessing the first tty for a gsm0710 multiplexed serial device is not
> currently possible, which makes it racy to use with multiple modems.
> 
> Add a way to map the physical serial tty to its related mux devices
> using an ioctl.
> 
> Signed-off-by: Martin Hundebøll <martin@geanix.com>
> ---
> 
> Changes since v2:
>  * rename IOCTL from GSMIOC_GETBASE to GSMIOC_GETFIRST
>  * return first usable line instead of private control line
>  * return uint32_t instead of int
> 
> Changes since v1:
>  * use put_user() instead of copy_to_user()
>  * add missing opening quote
> 
>  Documentation/serial/n_gsm.rst | 11 +++++++++--
>  drivers/tty/n_gsm.c            |  4 ++++
>  include/uapi/linux/gsmmux.h    |  2 ++
>  3 files changed, 15 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/serial/n_gsm.rst b/Documentation/serial/n_gsm.rst
> index 0ba731ab00b2..286e7ff4d2d9 100644
> --- a/Documentation/serial/n_gsm.rst
> +++ b/Documentation/serial/n_gsm.rst
> @@ -18,10 +18,13 @@ How to use it
>  2. switch the serial line to using the n_gsm line discipline by using
>     TIOCSETD ioctl,
>  3. configure the mux using GSMIOC_GETCONF / GSMIOC_SETCONF ioctl,
> +4. obtain base gsmtty number for the used serial port,

As this file is in .rst format, do we need the enumerated list anymore?

Just a meta-comment...

>  
>  Major parts of the initialization program :
>  (a good starting point is util-linux-ng/sys-utils/ldattach.c)::
>  
> +  #include <stdio.h>
> +  #include <stdint.h>
>    #include <linux/gsmmux.h>
>    #include <linux/tty.h>
>    #define DEFAULT_SPEED	B115200
> @@ -30,6 +33,7 @@ Major parts of the initialization program :
>  	int ldisc = N_GSM0710;
>  	struct gsm_config c;
>  	struct termios configuration;
> +	uint32_t first;
>  
>  	/* open the serial port connected to the modem */
>  	fd = open(SERIAL_PORT, O_RDWR | O_NOCTTY | O_NDELAY);
> @@ -58,19 +62,22 @@ Major parts of the initialization program :
>  	c.mtu = 127;
>  	/* set the new configuration */
>  	ioctl(fd, GSMIOC_SETCONF, &c);
> +	/* get first gsmtty device node */
> +	ioctl(fd, GSMIOC_GETFIRST, &first);
> +	printf("first muxed line: /dev/gsmtty%i\n", first);
>  
>  	/* and wait for ever to keep the line discipline enabled */
>  	daemon(0,0);
>  	pause();
>  
> -4. use these devices as plain serial ports.
> +5. use these devices as plain serial ports.
>  
>     for example, it's possible:
>  
>     - and to use gnokii to send / receive SMS on ttygsm1
>     - to use ppp to establish a datalink on ttygsm2
>  
> -5. first close all virtual ports before closing the physical port.
> +6. first close all virtual ports before closing the physical port.
>  
>     Note that after closing the physical port the modem is still in multiplexing
>     mode. This may prevent a successful re-opening of the port later. To avoid
> diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
> index a60be591f1fc..dac98f3ead3d 100644
> --- a/drivers/tty/n_gsm.c
> +++ b/drivers/tty/n_gsm.c
> @@ -2613,6 +2613,7 @@ static int gsmld_ioctl(struct tty_struct *tty, struct file *file,
>  {
>  	struct gsm_config c;
>  	struct gsm_mux *gsm = tty->disc_data;
> +	unsigned int base;
>  
>  	switch (cmd) {
>  	case GSMIOC_GETCONF:
> @@ -2624,6 +2625,9 @@ static int gsmld_ioctl(struct tty_struct *tty, struct file *file,
>  		if (copy_from_user(&c, (void *)arg, sizeof(c)))
>  			return -EFAULT;
>  		return gsm_config(gsm, &c);
> +	case GSMIOC_GETFIRST:
> +		base = mux_num_to_base(gsm);
> +		return put_user(base + 1, (uint32_t __user *)arg);




>  	default:
>  		return n_tty_ioctl_helper(tty, file, cmd, arg);
>  	}
> diff --git a/include/uapi/linux/gsmmux.h b/include/uapi/linux/gsmmux.h
> index 101d3c469acb..e292869245dc 100644
> --- a/include/uapi/linux/gsmmux.h
> +++ b/include/uapi/linux/gsmmux.h
> @@ -37,5 +37,7 @@ struct gsm_netconfig {
>  #define GSMIOC_ENABLE_NET      _IOW('G', 2, struct gsm_netconfig)
>  #define GSMIOC_DISABLE_NET     _IO('G', 3)
>  
> +/* get the base tty number for a configured gsmmux tty */
> +#define GSMIOC_GETFIRST		_IOR('G', 4, uint32_t)

Variables that cross the boundry from user/kernel should use the correct
type.  That would be "__u32" here.

thanks.

greg k-h