[PATCHv2 1/4] tty: n_gsm: remove obsolete mknod doc example

[PATCHv2 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>
---

Changes since v1:
 * updated bullet numbering

 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

[PATCHv2 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

[PATCHv2 3/4] tty: n_gsm: add helper 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 function instead of shifting 6 bits.

Signed-off-by: Martin Hundebøll <martin@geanix.com>
---
 drivers/tty/n_gsm.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index c4e16b31f9ab..cba06063c44a 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 int mux_num_to_base(struct gsm_mux *gsm)
+{
+	return gsm->num * NUM_DLCI;
+}
+
+static inline unsigned int mux_line_to_num(int line)
+{
+	return line / NUM_DLCI;
+}
+
 /**
  *	gsm_alloc_mux		-	allocate a mux
  *
@@ -2361,7 +2371,7 @@ 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);
 	}
@@ -2380,7 +2390,7 @@ 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)
 {
 	int i;
-	int base = gsm->num << 6; /* Base for this MUX */
+	int base = mux_num_to_base(gsm); /* Base for this MUX */
 
 	WARN_ON(tty != gsm->tty);
 	for (i = 1; i < NUM_DLCI; i++)
@@ -2908,7 +2918,7 @@ 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

[PATCHv2 4/4] tty: n_gsm: add ioctl to map serial device to mux'ed tty

[Martin Hundebøll]

Guessing the base 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 a ioctl.

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

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

 Documentation/serial/n_gsm.rst | 12 ++++++++++--
 drivers/tty/n_gsm.c            |  4 ++++
 include/uapi/linux/gsmmux.h    |  2 ++
 3 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/Documentation/serial/n_gsm.rst b/Documentation/serial/n_gsm.rst
index 0ba731ab00b2..4a52499567f5 100644
--- a/Documentation/serial/n_gsm.rst
+++ b/Documentation/serial/n_gsm.rst
@@ -18,10 +18,12 @@ 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 <linux/gsmmux.h>
   #include <linux/tty.h>
   #define DEFAULT_SPEED	B115200
@@ -30,6 +32,7 @@ Major parts of the initialization program :
 	int ldisc = N_GSM0710;
 	struct gsm_config c;
 	struct termios configuration;
+	int base;
 
 	/* open the serial port connected to the modem */
 	fd = open(SERIAL_PORT, O_RDWR | O_NOCTTY | O_NDELAY);
@@ -58,19 +61,24 @@ Major parts of the initialization program :
 	c.mtu = 127;
 	/* set the new configuration */
 	ioctl(fd, GSMIOC_SETCONF, &c);
+	/* get base gsmtty device node */
+	ioctl(fd, GSMIOC_GETBASE, &base);
+	/* the base node is used for mux control by the driver */
+	printf("first muxed line: /dev/gsmtty%i\n", base + 1);
+
 
 	/* 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 cba06063c44a..e7aea4ccbebd 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -2612,6 +2612,7 @@ static int gsmld_ioctl(struct tty_struct *tty, struct file *file,
 {
 	struct gsm_config c;
 	struct gsm_mux *gsm = tty->disc_data;
+	int base;
 
 	switch (cmd) {
 	case GSMIOC_GETCONF:
@@ -2623,6 +2624,9 @@ 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_GETBASE:
+		base = mux_num_to_base(gsm);
+		return put_user(base, (int __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..6eb63be3ed9e 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_GETBASE		_IOR('G', 4, int)
 
 #endif
-- 
2.22.0

Re: [PATCHv2 4/4] tty: n_gsm: add ioctl to map serial device to mux'ed tty

[Jiri Slaby]

On 09. 07. 19, 8:46, Martin Hundebøll  wrote:
> @@ -2623,6 +2624,9 @@ 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_GETBASE:
> +		base = mux_num_to_base(gsm);
> +		return put_user(base, (int __user *)arg);

I am not sure, but do you need the local variable at all?

>  	default:
>  		return n_tty_ioctl_helper(tty, file, cmd, arg);
>  	}


-- 
js
suse labs

Re: [PATCHv2 4/4] tty: n_gsm: add ioctl to map serial device to mux'ed tty

[Martin Hundebøll]

On 09/07/2019 08.49, Jiri Slaby wrote:
> On 09. 07. 19, 8:46, Martin Hundebøll  wrote:
>> @@ -2623,6 +2624,9 @@ 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_GETBASE:
>> +		base = mux_num_to_base(gsm);
>> +		return put_user(base, (int __user *)arg);
> I am not sure, but do you need the local variable at all?

No, I kept it around just to avoid too many parenthesis in the 
put_user() call.

Your call.

// Martin

Re: [PATCHv2 3/4] tty: n_gsm: add helper to convert mux-num to/from tty-base

[Alan Cox]

On Tue,  9 Jul 2019 08:46:32 +0200
Martin Hundebøll <martin@geanix.com> wrote:

> Make it obvious how the gsm mux number relates to the virtual tty lines
> by using helper function instead of shifting 6 bits.
> 
> Signed-off-by: Martin Hundebøll <martin@geanix.com>
> ---
>  drivers/tty/n_gsm.c | 16 +++++++++++++---
>  1 file changed, 13 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
> index c4e16b31f9ab..cba06063c44a 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 int mux_num_to_base(struct gsm_mux *gsm)
> +{
> +	return gsm->num * NUM_DLCI;
> +}
> +
> +static inline unsigned int mux_line_to_num(int line)
> +{
> +	return line / NUM_DLCI;

If you are going to convert shifts to multiply and divide then used
unsigned maths so the compiler can optimize it nicely on some of the low
end processors.

Alan