[PATCH v5 01/10] tty: n_gsm: add restart flag to DLC specific ioctl config

[PATCH v5 01/10] tty: n_gsm: add restart flag to DLC specific ioctl config

[D. Starke]

From: Daniel Starke <daniel.starke@siemens.com>

Currently, changing the parameters of a DLCI gives no direct control to the
user whether this should trigger a channel reset or not. The decision is
solely made by the driver based on the assumption which parameter changes
are compatible or not. Therefore, the user has no means to perform an
automatic channel reset after parameter configuration for non-conflicting
changes.

Add the parameter 'flags' to 'gsm_dlci_config' to force a channel reset
after ioctl setting regardless of whether the changes made require this or
not by setting this to 'GSM_FL_RESTART'.

Note that 'GSM_FL_RESTART' is currently the only allow flag to allow
additions here.

Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
---
 drivers/tty/n_gsm.c         |  4 ++++
 include/uapi/linux/gsmmux.h | 15 ++++++++++++++-
 2 files changed, 18 insertions(+), 1 deletion(-)

v4 -> v5:
Changed GSM_FL_RESTART comment to be more specific about its use as
suggested in the review comment.

Please note that I cannot response to emails until August 7th. Felix Haase
will take over from our side for questions regarding this patch series or
the n_gsm.

Link: https://lore.kernel.org/all/DB9PR10MB5881B63FBBA7912DF5A7A6A8E0789@DB9PR10MB5881.EURPRD10.PROD.OUTLOOK.COM/

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index b411a26cc092..66edcf65a4dd 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -2532,6 +2532,8 @@ static int gsm_dlci_config(struct gsm_dlci *dlci, struct gsm_dlci_config *dc, in
 		return -EINVAL;
 	if (dc->k > 7)
 		return -EINVAL;
+	if (dc->flags & ~GSM_FL_RESTART)   /* allow future extensions */
+		return -EINVAL;
 
 	/*
 	 * See what is needed for reconfiguration
@@ -2546,6 +2548,8 @@ static int gsm_dlci_config(struct gsm_dlci *dlci, struct gsm_dlci_config *dc, in
 	/* Requires care */
 	if (dc->priority != dlci->prio)
 		need_restart = true;
+	if (dc->flags & GSM_FL_RESTART)
+		need_restart = true;
 
 	if ((open && gsm->wait_config) || need_restart)
 		need_open = true;
diff --git a/include/uapi/linux/gsmmux.h b/include/uapi/linux/gsmmux.h
index eb67884e5f38..e56e2d7ea6eb 100644
--- a/include/uapi/linux/gsmmux.h
+++ b/include/uapi/linux/gsmmux.h
@@ -2,10 +2,22 @@
 #ifndef _LINUX_GSMMUX_H
 #define _LINUX_GSMMUX_H
 
+#include <linux/const.h>
 #include <linux/if.h>
 #include <linux/ioctl.h>
 #include <linux/types.h>
 
+/*
+ * flags definition for n_gsm
+ *
+ * Used by:
+ * struct gsm_dlci_config.flags
+ */
+/* Forces a DLCI reset if set. Otherwise, a DLCI reset is only done if
+ * incompatible settings were provided. Always cleared on retrieval.
+ */
+#define GSM_FL_RESTART	_BITUL(0)
+
 struct gsm_config
 {
 	unsigned int adaption;
@@ -58,7 +70,8 @@ struct gsm_dlci_config {
 	__u32 priority;		/* Priority (0 for default value) */
 	__u32 i;		/* Frame type (1 = UIH, 2 = UI) */
 	__u32 k;		/* Window size (0 for default value) */
-	__u32 reserved[8];	/* For future use, must be initialized to zero */
+	__u32 flags;		/* DLCI specific flags. */
+	__u32 reserved[7];	/* For future use, must be initialized to zero */
 };
 
 #define GSMIOC_GETCONF_DLCI	_IOWR('G', 7, struct gsm_dlci_config)
-- 
2.34.1

[PATCH v5 02/10] tty: n_gsm: add missing description to structs in gsmmux.h

[D. Starke]

From: Daniel Starke <daniel.starke@siemens.com>

Currently, all available structure fields in gsmmux.h except those
for gsm_config are commented. Furthermore, no kernel doc comments are used.

Fix this by adding appropriate comments to the not commented fields of
gsm_config. Convert the comments of the other structs to kernel doc format.

Note that 'mru' and 'mtu' refer to the size without basic/advanced option
mode header and byte stuffing as defined in the standard in chapter 5.7.2.

Link: https://portal.3gpp.org/desktopmodules/Specifications/SpecificationDetails.aspx?specificationId=1516
Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
---
 include/uapi/linux/gsmmux.h | 104 +++++++++++++++++++++++++++++-------
 1 file changed, 84 insertions(+), 20 deletions(-)

v4 -> v5:
No changes.

Please note that I cannot response to emails until August 7th. Felix Haase
will take over from our side for questions regarding this patch series or
the n_gsm.

Link: https://lore.kernel.org/all/20230426080315.7595-2-daniel.starke@siemens.com/

diff --git a/include/uapi/linux/gsmmux.h b/include/uapi/linux/gsmmux.h
index e56e2d7ea6eb..3bd6f03a8293 100644
--- a/include/uapi/linux/gsmmux.h
+++ b/include/uapi/linux/gsmmux.h
@@ -18,6 +18,28 @@
  */
 #define GSM_FL_RESTART	_BITUL(0)
 
+/**
+ * struct gsm_config - n_gsm basic configuration parameters
+ *
+ * This structure is used in combination with GSMIOC_GETCONF and GSMIOC_SETCONF
+ * to retrieve and set the basic parameters of an n_gsm ldisc.
+ * struct gsm_config_ext can be used to configure extended ldisc parameters.
+ *
+ * All timers are in units of 1/100th of a second.
+ *
+ * @adaption:      Convergence layer type
+ * @encapsulation: Framing (0 = basic option, 1 = advanced option)
+ * @initiator:     Initiator or responder
+ * @t1:            Acknowledgment timer
+ * @t2:            Response timer for multiplexer control channel
+ * @t3:            Response timer for wake-up procedure
+ * @n2:            Maximum number of retransmissions
+ * @mru:           Maximum incoming frame payload size
+ * @mtu:           Maximum outgoing frame payload size
+ * @k:             Window size
+ * @i:             Frame type (1 = UIH, 2 = UI)
+ * @unused:        Can not be used
+ */
 struct gsm_config
 {
 	unsigned int adaption;
@@ -31,18 +53,32 @@ struct gsm_config
 	unsigned int mtu;
 	unsigned int k;
 	unsigned int i;
-	unsigned int unused[8];	/* Can not be used */
+	unsigned int unused[8];
 };
 
 #define GSMIOC_GETCONF		_IOR('G', 0, struct gsm_config)
 #define GSMIOC_SETCONF		_IOW('G', 1, struct gsm_config)
 
+/**
+ * struct gsm_netconfig - n_gsm network configuration parameters
+ *
+ * This structure is used in combination with GSMIOC_ENABLE_NET and
+ * GSMIOC_DISABLE_NET to enable or disable a network data connection
+ * over a mux virtual tty channel. This is for modems that support
+ * data connections with raw IP frames instead of PPP.
+ *
+ * @adaption: Adaption to use in network mode.
+ * @protocol: Protocol to use - only ETH_P_IP supported.
+ * @unused2:  Can not be used.
+ * @if_name:  Interface name format string.
+ * @unused:   Can not be used.
+ */
 struct gsm_netconfig {
-	unsigned int adaption;  /* Adaption to use in network mode */
-	unsigned short protocol;/* Protocol to use - only ETH_P_IP supported */
-	unsigned short unused2;	/* Can not be used */
-	char if_name[IFNAMSIZ];	/* interface name format string */
-	__u8 unused[28];        /* Can not be used */
+	unsigned int adaption;
+	unsigned short protocol;
+	unsigned short unused2;
+	char if_name[IFNAMSIZ];
+	__u8 unused[28];
 };
 
 #define GSMIOC_ENABLE_NET      _IOW('G', 2, struct gsm_netconfig)
@@ -51,27 +87,55 @@ struct gsm_netconfig {
 /* get the base tty number for a configured gsmmux tty */
 #define GSMIOC_GETFIRST		_IOR('G', 4, __u32)
 
+/**
+ * struct gsm_config_ext - n_gsm extended configuration parameters
+ *
+ * This structure is used in combination with GSMIOC_GETCONF_EXT and
+ * GSMIOC_SETCONF_EXT to retrieve and set the extended parameters of an
+ * n_gsm ldisc.
+ *
+ * All timers are in units of 1/100th of a second.
+ *
+ * @keep_alive:  Control channel keep-alive in 1/100th of a second (0 to disable).
+ * @wait_config: Wait for DLCI config before opening virtual link?
+ * @reserved:    For future use, must be initialized to zero.
+ */
 struct gsm_config_ext {
-	__u32 keep_alive;	/* Control channel keep-alive in 1/100th of a
-				 * second (0 to disable)
-				 */
-	__u32 wait_config;	/* Wait for DLCI config before opening virtual link? */
-	__u32 reserved[6];	/* For future use, must be initialized to zero */
+	__u32 keep_alive;
+	__u32 wait_config;
+	__u32 reserved[6];
 };
 
 #define GSMIOC_GETCONF_EXT	_IOR('G', 5, struct gsm_config_ext)
 #define GSMIOC_SETCONF_EXT	_IOW('G', 6, struct gsm_config_ext)
 
-/* Set channel accordingly before calling GSMIOC_GETCONF_DLCI. */
+/**
+ * struct gsm_dlci_config - n_gsm channel configuration parameters
+ *
+ * This structure is used in combination with GSMIOC_GETCONF_DLCI and
+ * GSMIOC_SETCONF_DLCI to retrieve and set the channel specific parameters
+ * of an n_gsm ldisc.
+ *
+ * Set the channel accordingly before calling GSMIOC_GETCONF_DLCI.
+ *
+ * @channel:  DLCI (0 for the associated DLCI).
+ * @adaption: Convergence layer type.
+ * @mtu:      Maximum transfer unit.
+ * @priority: Priority (0 for default value).
+ * @i:        Frame type (1 = UIH, 2 = UI).
+ * @k:        Window size (0 for default value).
+ * @flags:    DLCI specific flags.
+ * @reserved: For future use, must be initialized to zero.
+ */
 struct gsm_dlci_config {
-	__u32 channel;		/* DLCI (0 for the associated DLCI) */
-	__u32 adaption;		/* Convergence layer type */
-	__u32 mtu;		/* Maximum transfer unit */
-	__u32 priority;		/* Priority (0 for default value) */
-	__u32 i;		/* Frame type (1 = UIH, 2 = UI) */
-	__u32 k;		/* Window size (0 for default value) */
-	__u32 flags;		/* DLCI specific flags. */
-	__u32 reserved[7];	/* For future use, must be initialized to zero */
+	__u32 channel;
+	__u32 adaption;
+	__u32 mtu;
+	__u32 priority;
+	__u32 i;
+	__u32 k;
+	__u32 flags;
+	__u32 reserved[7];
 };
 
 #define GSMIOC_GETCONF_DLCI	_IOWR('G', 7, struct gsm_dlci_config)
-- 
2.34.1

[PATCH v5 03/10] tty: n_gsm: remove unneeded initialization of ret in gsm_dlci_config

[D. Starke]

From: Daniel Starke <daniel.starke@siemens.com>

The variable 'ret' is not used before assignment from gsm_activate_mux().
Still it gets initialized to zero at declaration.

Fix this as remarked in the link below by moving the declaration to the
first assignment.

Link: https://lore.kernel.org/all/b42bc4d1-cc9d-d115-c981-aaa053bdc59f@kernel.org/

Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
---
 drivers/tty/n_gsm.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

v4 -> v5:
No changes.

Please note that I cannot response to emails until August 7th. Felix Haase
will take over from our side for questions regarding this patch series or
the n_gsm.

Link: https://lore.kernel.org/all/20230426080315.7595-3-daniel.starke@siemens.com/

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 66edcf65a4dd..ebb71957f783 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -3277,7 +3277,6 @@ static void gsm_copy_config_values(struct gsm_mux *gsm,
 
 static int gsm_config(struct gsm_mux *gsm, struct gsm_config *c)
 {
-	int ret = 0;
 	int need_close = 0;
 	int need_restart = 0;
 
@@ -3356,7 +3355,7 @@ static int gsm_config(struct gsm_mux *gsm, struct gsm_config *c)
 	 * and removing from the mux array
 	 */
 	if (gsm->dead) {
-		ret = gsm_activate_mux(gsm);
+		int ret = gsm_activate_mux(gsm);
 		if (ret)
 			return ret;
 		if (gsm->initiator)
-- 
2.34.1

[PATCH v5 04/10] tty: n_gsm: add open_error counter to gsm_mux

[D. Starke]

From: Daniel Starke <daniel.starke@siemens.com>

Extend the n_gsm link statistics by a failed link open counter in
preparation for an upcoming patch which will expose these.
This counter is increased whenever an attempt to open the control channel
failed. This is true in the following cases:
- new DLCI allocation failed
- connection request (SAMB) with invalid CR flag has been received
- connection response (UA) timed out
- parameter negotiation timed out or failed

Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
---
 drivers/tty/n_gsm.c | 25 ++++++++++++++++++++-----
 1 file changed, 20 insertions(+), 5 deletions(-)

v4 -> v5:
No changes.

Please note that I cannot response to emails until August 7th. Felix Haase
will take over from our side for questions regarding this patch series or
the n_gsm.

Link: https://lore.kernel.org/all/20230426080315.7595-4-daniel.starke@siemens.com/

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index ebb71957f783..186f463f0f11 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -339,6 +339,7 @@ struct gsm_mux {
 	unsigned long bad_fcs;
 	unsigned long malformed;
 	unsigned long io_error;
+	unsigned long open_error;
 	unsigned long bad_size;
 	unsigned long unsupported;
 };
@@ -1730,25 +1731,32 @@ static void gsm_control_negotiation(struct gsm_mux *gsm, unsigned int cr,
 	struct gsm_dlci *dlci;
 	struct gsm_dlci_param_bits *params;
 
-	if (dlen < sizeof(struct gsm_dlci_param_bits))
+	if (dlen < sizeof(struct gsm_dlci_param_bits)) {
+		gsm->open_error++;
 		return;
+	}
 
 	/* Invalid DLCI? */
 	params = (struct gsm_dlci_param_bits *)data;
 	addr = FIELD_GET(PN_D_FIELD_DLCI, params->d_bits);
-	if (addr == 0 || addr >= NUM_DLCI || !gsm->dlci[addr])
+	if (addr == 0 || addr >= NUM_DLCI || !gsm->dlci[addr]) {
+		gsm->open_error++;
 		return;
+	}
 	dlci = gsm->dlci[addr];
 
 	/* Too late for parameter negotiation? */
-	if ((!cr && dlci->state == DLCI_OPENING) || dlci->state == DLCI_OPEN)
+	if ((!cr && dlci->state == DLCI_OPENING) || dlci->state == DLCI_OPEN) {
+		gsm->open_error++;
 		return;
+	}
 
 	/* Process the received parameters */
 	if (gsm_process_negotiation(gsm, addr, cr, params) != 0) {
 		/* Negotiation failed. Close the link. */
 		if (debug & DBG_ERRORS)
 			pr_info("%s PN failed\n", __func__);
+		gsm->open_error++;
 		gsm_dlci_close(dlci);
 		return;
 	}
@@ -1768,6 +1776,7 @@ static void gsm_control_negotiation(struct gsm_mux *gsm, unsigned int cr,
 	} else {
 		if (debug & DBG_ERRORS)
 			pr_info("%s PN in invalid state\n", __func__);
+		gsm->open_error++;
 	}
 }
 
@@ -2221,6 +2230,7 @@ static void gsm_dlci_t1(struct timer_list *t)
 			dlci->retries--;
 			mod_timer(&dlci->t1, jiffies + gsm->t1 * HZ / 100);
 		} else {
+			gsm->open_error++;
 			gsm_dlci_begin_close(dlci); /* prevent half open link */
 		}
 		break;
@@ -2236,6 +2246,7 @@ static void gsm_dlci_t1(struct timer_list *t)
 			dlci->mode = DLCI_MODE_ADM;
 			gsm_dlci_open(dlci);
 		} else {
+			gsm->open_error++;
 			gsm_dlci_begin_close(dlci); /* prevent half open link */
 		}
 
@@ -2757,12 +2768,16 @@ static void gsm_queue(struct gsm_mux *gsm)
 
 	switch (gsm->control) {
 	case SABM|PF:
-		if (cr == 1)
+		if (cr == 1) {
+			gsm->open_error++;
 			goto invalid;
+		}
 		if (dlci == NULL)
 			dlci = gsm_dlci_alloc(gsm, address);
-		if (dlci == NULL)
+		if (dlci == NULL) {
+			gsm->open_error++;
 			return;
+		}
 		if (dlci->dead)
 			gsm_response(gsm, address, DM|PF);
 		else {
-- 
2.34.1

[PATCH v5 05/10] tty: n_gsm: increase malformed counter for malformed control frames

[D. Starke]

From: Daniel Starke <daniel.starke@siemens.com>

The malformed counter in gsm_mux is already increased in case of errors
detected in gsm_queue() and gsm1_receive(). gsm_dlci_command() also
detects a case for a malformed frame but does not increase the malformed
counter yet.

Fix this by also increasing the gsm_mux malformed counter in case of a
malformed frame in gsm_dlci_command().
Note that the malformed counter is not yet exposed and only set internally.

Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
---
 drivers/tty/n_gsm.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

v4 -> v5:
No changes.

Please note that I cannot response to emails until August 7th. Felix Haase
will take over from our side for questions regarding this patch series or
the n_gsm.

Link: https://lore.kernel.org/all/20230426080315.7595-5-daniel.starke@siemens.com/

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 186f463f0f11..5b6a03668c78 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -2455,8 +2455,10 @@ static void gsm_dlci_command(struct gsm_dlci *dlci, const u8 *data, int len)
 	data += dlen;
 
 	/* Malformed command? */
-	if (clen > len)
+	if (clen > len) {
+		dlci->gsm->malformed++;
 		return;
+	}
 
 	if (command & 1)
 		gsm_control_message(dlci->gsm, command, data, clen);
-- 
2.34.1

[PATCH v5 06/10] tty: n_gsm: increase gsm_mux unsupported counted where appropriate

[D. Starke]

From: Daniel Starke <daniel.starke@siemens.com>

The structure gsm_mux contains the 'unsupported' field. However, there is
currently no place in the code which increases this counter.

Increase the 'unsupported' statistics counter in the following case:
- an unsupported frame type has been requested by the peer via parameter
  negotiation
- a control frame with an unsupported but known command has been received

Note that we have no means to detect an inconsistent/unsupported adaptation
sufficient accuracy as this changes the structure of the UI/UIH frames.
E.g. a one byte header is added in case of convergence layer type 2 instead
of 1 and contains the modem signal octet with the state of the signal
lines. There is no checksum or other value which indicates of this field is
correct or should be present. Therefore, we can only assume protocol
correctness here. See also 'gsm_dlci_data()' where this is handled.

Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
---
 drivers/tty/n_gsm.c | 3 +++
 1 file changed, 3 insertions(+)

v4 -> v5:
No changes.

Please note that I cannot response to emails until August 7th. Felix Haase
will take over from our side for questions regarding this patch series or
the n_gsm.

Link: https://lore.kernel.org/all/20230426080315.7595-6-daniel.starke@siemens.com/

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 5b6a03668c78..42a8507aae4a 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -1590,6 +1590,7 @@ static int gsm_process_negotiation(struct gsm_mux *gsm, unsigned int addr,
 		if (debug & DBG_ERRORS)
 			pr_info("%s unsupported I frame request in PN\n",
 				__func__);
+		gsm->unsupported++;
 		return -EINVAL;
 	default:
 		if (debug & DBG_ERRORS)
@@ -1897,6 +1898,8 @@ static void gsm_control_message(struct gsm_mux *gsm, unsigned int command,
 		/* Optional unsupported commands */
 	case CMD_RPN:	/* Remote port negotiation */
 	case CMD_SNC:	/* Service negotiation command */
+		gsm->unsupported++;
+		fallthrough;
 	default:
 		/* Reply to bad commands with an NSC */
 		buf[0] = command;
-- 
2.34.1

[PATCH v5 07/10] tty: n_gsm: cleanup gsm_control_command and gsm_control_reply

[D. Starke]

From: Daniel Starke <daniel.starke@siemens.com>

There are multiple places in gsm_control_command and gsm_control_reply that
derive the specific DLCI handle directly out of the DLCI table in gsm.

Add a local variable which holds this handle and use it instead to improve
code readability.

Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
---
 drivers/tty/n_gsm.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

v4 -> v5:
No changes.

Please note that I cannot response to emails until August 7th. Felix Haase
will take over from our side for questions regarding this patch series or
the n_gsm.

Link: https://lore.kernel.org/all/20230426080315.7595-7-daniel.starke@siemens.com/

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 42a8507aae4a..62bff4474b57 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -1451,15 +1451,16 @@ static int gsm_control_command(struct gsm_mux *gsm, int cmd, const u8 *data,
 			       int dlen)
 {
 	struct gsm_msg *msg;
+	struct gsm_dlci *dlci = gsm->dlci[0];
 
-	msg = gsm_data_alloc(gsm, 0, dlen + 2, gsm->dlci[0]->ftype);
+	msg = gsm_data_alloc(gsm, 0, dlen + 2, dlci->ftype);
 	if (msg == NULL)
 		return -ENOMEM;
 
 	msg->data[0] = (cmd << 1) | CR | EA;	/* Set C/R */
 	msg->data[1] = (dlen << 1) | EA;
 	memcpy(msg->data + 2, data, dlen);
-	gsm_data_queue(gsm->dlci[0], msg);
+	gsm_data_queue(dlci, msg);
 
 	return 0;
 }
@@ -1478,14 +1479,15 @@ static void gsm_control_reply(struct gsm_mux *gsm, int cmd, const u8 *data,
 					int dlen)
 {
 	struct gsm_msg *msg;
+	struct gsm_dlci *dlci = gsm->dlci[0];
 
-	msg = gsm_data_alloc(gsm, 0, dlen + 2, gsm->dlci[0]->ftype);
+	msg = gsm_data_alloc(gsm, 0, dlen + 2, dlci->ftype);
 	if (msg == NULL)
 		return;
 	msg->data[0] = (cmd & 0xFE) << 1 | EA;	/* Clear C/R */
 	msg->data[1] = (dlen << 1) | EA;
 	memcpy(msg->data + 2, data, dlen);
-	gsm_data_queue(gsm->dlci[0], msg);
+	gsm_data_queue(dlci, msg);
 }
 
 /**
-- 
2.34.1

[PATCH v5 08/10] tty: n_gsm: add DLCI specific rx/tx statistics

[D. Starke]

From: Daniel Starke <daniel.starke@siemens.com>

Add counters for the number of data bytes received/transmitted per DLCI in
for preparation for an upcoming patch which will expose these values to the
user.

Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
---
 drivers/tty/n_gsm.c | 26 +++++++++++++++++++++++++-
 1 file changed, 25 insertions(+), 1 deletion(-)

v4 -> v5:
Added blank line before comment of new tx/rx fields in struct gsm_dlci as
suggested in the review.
The remarked upcoming patch which exposes these flags is now included in
patch 9/10. This has been done as recommended in the review.

Please note that I cannot response to emails until August 7th. Felix Haase
will take over from our side for questions regarding this patch series or
the n_gsm.

Link: https://lore.kernel.org/all/DB9PR10MB5881A7A09725EAF8FDB5F35BE0789@DB9PR10MB5881.EURPRD10.PROD.OUTLOOK.COM/

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 62bff4474b57..511f22489754 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -186,6 +186,10 @@ struct gsm_dlci {
 	void (*data)(struct gsm_dlci *dlci, const u8 *data, int len);
 	void (*prev_data)(struct gsm_dlci *dlci, const u8 *data, int len);
 	struct net_device *net; /* network interface, if created */
+
+	/* Statistics (not currently exposed) */
+	u64 tx;			/* Data bytes sent on this DLCI */
+	u64 rx;			/* Data bytes received on this DLCI */
 };
 
 /*
@@ -1216,6 +1220,7 @@ static int gsm_dlci_data_output(struct gsm_mux *gsm, struct gsm_dlci *dlci)
 	tty_port_tty_wakeup(&dlci->port);
 
 	__gsm_data_queue(dlci, msg);
+	dlci->tx += len;
 	/* Bytes of data we used up */
 	return size;
 }
@@ -1283,6 +1288,7 @@ static int gsm_dlci_data_output_framed(struct gsm_mux *gsm,
 	memcpy(dp, dlci->skb->data, len);
 	skb_pull(dlci->skb, len);
 	__gsm_data_queue(dlci, msg);
+	dlci->tx += len;
 	if (last) {
 		dev_kfree_skb_any(dlci->skb);
 		dlci->skb = NULL;
@@ -1461,6 +1467,7 @@ static int gsm_control_command(struct gsm_mux *gsm, int cmd, const u8 *data,
 	msg->data[1] = (dlen << 1) | EA;
 	memcpy(msg->data + 2, data, dlen);
 	gsm_data_queue(dlci, msg);
+	dlci->tx += dlen;
 
 	return 0;
 }
@@ -1488,6 +1495,7 @@ static void gsm_control_reply(struct gsm_mux *gsm, int cmd, const u8 *data,
 	msg->data[1] = (dlen << 1) | EA;
 	memcpy(msg->data + 2, data, dlen);
 	gsm_data_queue(dlci, msg);
+	dlci->tx += dlen;
 }
 
 /**
@@ -1852,10 +1860,13 @@ static void gsm_control_message(struct gsm_mux *gsm, unsigned int command,
 						const u8 *data, int clen)
 {
 	u8 buf[1];
+	struct gsm_dlci *dlci = gsm->dlci[0];
+
+	if (dlci)
+		dlci->rx += clen;
 
 	switch (command) {
 	case CMD_CLD: {
-		struct gsm_dlci *dlci = gsm->dlci[0];
 		/* Modem wishes to close down */
 		if (dlci) {
 			dlci->dead = true;
@@ -1934,6 +1945,8 @@ static void gsm_control_response(struct gsm_mux *gsm, unsigned int command,
 
 	ctrl = gsm->pending_cmd;
 	dlci = gsm->dlci[0];
+	if (dlci)
+		dlci->rx += clen;
 	command |= 1;
 	/* Does the reply match our command */
 	if (ctrl != NULL && (command == ctrl->cmd || command == CMD_NSC)) {
@@ -2298,6 +2311,9 @@ static void gsm_dlci_begin_open(struct gsm_dlci *dlci)
 			need_pn = true;
 	}
 
+	dlci->tx = 0;
+	dlci->rx = 0;
+
 	switch (dlci->state) {
 	case DLCI_CLOSED:
 	case DLCI_WAITING_CONFIG:
@@ -2330,6 +2346,9 @@ static void gsm_dlci_begin_open(struct gsm_dlci *dlci)
  */
 static void gsm_dlci_set_opening(struct gsm_dlci *dlci)
 {
+	dlci->tx = 0;
+	dlci->rx = 0;
+
 	switch (dlci->state) {
 	case DLCI_CLOSED:
 	case DLCI_WAITING_CONFIG:
@@ -2349,6 +2368,9 @@ static void gsm_dlci_set_opening(struct gsm_dlci *dlci)
  */
 static void gsm_dlci_set_wait_config(struct gsm_dlci *dlci)
 {
+	dlci->tx = 0;
+	dlci->rx = 0;
+
 	switch (dlci->state) {
 	case DLCI_CLOSED:
 	case DLCI_CLOSING:
@@ -2425,6 +2447,7 @@ static void gsm_dlci_data(struct gsm_dlci *dlci, const u8 *data, int clen)
 		fallthrough;
 	case 1:		/* Line state will go via DLCI 0 controls only */
 	default:
+		dlci->rx += clen;
 		tty_insert_flip_string(port, data, clen);
 		tty_flip_buffer_push(port);
 	}
@@ -2785,6 +2808,7 @@ static void gsm_queue(struct gsm_mux *gsm)
 			gsm->open_error++;
 			return;
 		}
+		dlci->rx += gsm->len;
 		if (dlci->dead)
 			gsm_response(gsm, address, DM|PF);
 		else {
-- 
2.34.1

[PATCH v5 09/10] tty: n_gsm: expose configuration and statistics via proc fs

[D. Starke]

From: Daniel Starke <daniel.starke@siemens.com>

The n_gsm mux collects various statistics about the mux and its channels.
These are currently not exposed to the user. There exists already a proc fs
path for tty ldiscs (/proc/tty/ldisc).

Extend this path by an 'n_gsm' node and create a proc file for each mux
instance if active. The file exposes protocol statistics and channel states
and configuration to the user. Mutex based locks are introduced to avoid
inconsistent states.

The following shows an example output:
 tty:ttyS1 flags:
 initiator:1 mode:1 mru:64 mtu:64 t1:10 t2:34 t3:10 n2:3 k:2 wc:0 ka:100
 bad_fcs:0 malformed:0 io_error:0 open_error:0 bad_size:0 unsupported:0

 dlci:0 state:OPEN cl:2 prio:0 i:UIH k:2 mtu:64 tx:35 rx:35

Description:
tty:         The underlying device used by this mux.
flags:       Tty flags relevant to the mux protocol.
initiator:   0 for responder, 1 for initiator.
mode:        0 for basic option mode, 1 for advanced option mode
mru:         Maximum receive unit size.
mtu:         Maximum transmission unit size.
t1:          Acknowledgment timer.
t2:          Response timer for multiplexer control channel.
t3:          Response timer for wake-up procedure.
n2:          Maximum number of retransmissions.
k:           Window size.
wc:          Wait for configuration before starting parameter negotiation?
ka:          Control channel keep-alive timer (0 if disabled).
bad_fcs:     Number of bad FCS.
malformed:   Number of malformed frames.
io_error:    Number of I/O errors on the underlying tty.
open_error:  Number of failed DLCI open attempts.
bad_size:    Number of n_gsm frames with bad size.
unsupported: Number of malformed control frames.
dlci:        Related channel number.
state:       Current channel state. Possible values are CLOSED,
             WAITING_CONFIG, CONFIGURE, OPENING, OPEN and CLOSING.
cl:          Convergence layer type.
prio:        Priority.
i:           Framing. Possible values are UI and UIH.
k:           Window size.
mtu:         Maximum transmission unit size.
tx:          Transmitted payload size in bytes (incl. convergence layer
             type header).
rx:          Received payload size in bytes (incl. convergence layer type
             header).

All timers are in 1/100th of a second units.

Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
---
 drivers/tty/n_gsm.c | 207 +++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 196 insertions(+), 11 deletions(-)

v4 -> v5:
Newly added patch to expose the collected statistics to the user via proc
fs.

Please note that I cannot response to emails until August 7th. Felix Haase
will take over from our side for questions regarding this patch series or
the n_gsm.

Link: https://lore.kernel.org/all/DB9PR10MB5881A7A09725EAF8FDB5F35BE0789@DB9PR10MB5881.EURPRD10.PROD.OUTLOOK.COM/

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 511f22489754..30f73ab2491f 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -46,10 +46,12 @@
 #include <linux/string.h>
 #include <linux/slab.h>
 #include <linux/poll.h>
+#include <linux/proc_fs.h>
 #include <linux/bitops.h>
 #include <linux/file.h>
 #include <linux/uaccess.h>
 #include <linux/module.h>
+#include <linux/stringify.h>
 #include <linux/timer.h>
 #include <linux/tty_flip.h>
 #include <linux/tty_driver.h>
@@ -187,7 +189,7 @@ struct gsm_dlci {
 	void (*prev_data)(struct gsm_dlci *dlci, const u8 *data, int len);
 	struct net_device *net; /* network interface, if created */
 
-	/* Statistics (not currently exposed) */
+	/* Statistics (exposed via proc file) */
 	u64 tx;			/* Data bytes sent on this DLCI */
 	u64 rx;			/* Data bytes received on this DLCI */
 };
@@ -272,6 +274,7 @@ enum gsm_mux_state {
 
 struct gsm_mux {
 	struct tty_struct *tty;		/* The tty our ldisc is bound to */
+	struct proc_dir_entry *proc;	/* Associated proc fs entry */
 	spinlock_t lock;
 	struct mutex mutex;
 	unsigned int num;
@@ -339,7 +342,7 @@ struct gsm_mux {
 	bool wait_config;	/* Wait for configuration by ioctl before DLCI open */
 	u32 keep_alive;		/* Control channel keep-alive in 10ms */
 
-	/* Statistics (not currently exposed) */
+	/* Statistics (exposed via proc file) */
 	unsigned long bad_fcs;
 	unsigned long malformed;
 	unsigned long io_error;
@@ -357,6 +360,7 @@ struct gsm_mux {
 #define MAX_MUX		4			/* 256 minors */
 static struct gsm_mux *gsm_mux[MAX_MUX];	/* GSM muxes */
 static DEFINE_SPINLOCK(gsm_mux_lock);
+static DEFINE_MUTEX(gsm_mux_mutex);
 
 static struct tty_driver *gsm_tty_driver;
 
@@ -3079,6 +3083,153 @@ static void gsm_error(struct gsm_mux *gsm)
 	gsm->io_error++;
 }
 
+/*
+ * Entry to the proc file system in tty/ldisc/n_gsm/
+ */
+
+static struct proc_dir_entry *proc_gsm;
+
+/**
+ * gsm_proc_print_flag	-	check and print termios flag
+ * @m: output handle
+ * @flags: termios flags
+ * @val: flag to check and print
+ * @str: string representation of val
+ * @first: does not need separator?
+ */
+static bool gsm_proc_print_flag(struct seq_file *m, unsigned short flags,
+				int val, const char *str, bool first)
+{
+	if ((flags & val) == 0)
+		return first;
+	if (!first)
+		seq_putc(m, '|');
+	seq_puts(m, str);
+	return false;
+}
+
+#define gsm_proc_print_flag_str(m, flags, val) \
+	(first = gsm_proc_print_flag((m), (flags), (val), __stringify(val), first))
+
+/**
+ * gsm_proc_show	-	output proc file
+ * @m: output handle
+ * @v: result from start
+ *
+ * Handles the output of /proc/tty/ldisc/n_gsm/mux%d
+ */
+static int gsm_proc_show(struct seq_file *m, void *v)
+{
+	struct gsm_mux *gsm = m->private;
+	struct gsm_dlci *dlci = NULL;
+	unsigned short flags;
+	int i;
+	bool first = true;
+	const char *state, *ftype;
+
+	if (!gsm)
+		return -ENODEV;
+
+	/* The proc file may get removed in gsm_cleanup_mux() if the connection
+	 * was closed. Early out here to avoid a deadlock.
+	 */
+	if (!mutex_trylock(&gsm_mux_mutex))
+		return -EBUSY;
+	if (!mutex_trylock(&gsm->mutex)) {
+		mutex_unlock(&gsm_mux_mutex);
+		return -EBUSY;
+	}
+
+	seq_printf(m, "tty:%s flags:", tty_name(gsm->tty));
+	flags = gsm->tty->termios.c_iflag;
+	gsm_proc_print_flag_str(m, flags, IGNBRK);
+	gsm_proc_print_flag_str(m, flags, IXON);
+	gsm_proc_print_flag_str(m, flags, IXOFF);
+	flags = gsm->tty->termios.c_cflag;
+	gsm_proc_print_flag_str(m, flags, CLOCAL);
+	gsm_proc_print_flag_str(m, flags, CRTSCTS);
+	seq_putc(m, '\n');
+
+	seq_printf(m, "initiator:%d mode:%d mru:%u mtu:%u t1:%d t2:%d t3:%d",
+		   gsm->initiator, gsm->encoding, gsm->mru, gsm->mtu, gsm->t1,
+		   gsm->t2, gsm->t3);
+	seq_printf(m, " n2:%d k:%d wc:%d ka:%u", gsm->n2, gsm->k,
+		   gsm->wait_config ? 1 : 0, gsm->keep_alive);
+	if (gsm->dead)
+		seq_puts(m, " DEAD");
+	seq_putc(m, '\n');
+
+	seq_printf(m, "bad_fcs:%lu malformed:%lu io_error:%lu open_error:%lu",
+		   gsm->bad_fcs, gsm->malformed, gsm->io_error,
+		   gsm->open_error);
+	seq_printf(m, " bad_size:%lu unsupported:%lu\n\n", gsm->bad_size,
+		   gsm->unsupported);
+
+	for (i = 0; i < NUM_DLCI; i++) {
+		dlci = gsm->dlci[i];
+		if (!dlci)
+			continue;
+		switch (dlci->state) {
+		case DLCI_CLOSED:
+			state = "CLOSED";
+			break;
+		case DLCI_WAITING_CONFIG:
+			state = "WAITING_CONFIG";
+			break;
+		case DLCI_CONFIGURE:
+			state = "CONFIGURE";
+			break;
+		case DLCI_OPENING:
+			state = "OPENING";
+			break;
+		case DLCI_OPEN:
+			state = "OPEN";
+			break;
+		case DLCI_CLOSING:
+			state = "CLOSING";
+			break;
+		default:
+			state = "???";
+			break;
+		}
+		switch (dlci->ftype) {
+		case UI:
+			ftype = "UI";
+			break;
+		case UIH:
+			ftype = "UIH";
+			break;
+		default:
+			ftype = "???";
+			break;
+		}
+		seq_printf(m, "dlci:%d state:%s cl:%d prio:%d i:%s k:%d mtu:%u",
+			   i, state, dlci->adaption, dlci->prio, ftype, dlci->k,
+			   dlci->mtu);
+		seq_printf(m, " tx:%llu rx:%llu", dlci->tx, dlci->rx);
+		if (dlci->dead)
+			seq_puts(m, " DEAD");
+		seq_putc(m, '\n');
+	}
+
+	mutex_unlock(&gsm->mutex);
+	mutex_unlock(&gsm_mux_mutex);
+
+	return 0;
+}
+
+static int gsm_proc_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, gsm_proc_show, pde_data(inode));
+}
+
+static const struct proc_ops gsm_proc_ops = {
+	.proc_open    = gsm_proc_open,
+	.proc_read    = seq_read,
+	.proc_lseek   = seq_lseek,
+	.proc_release = single_release,
+};
+
 /**
  *	gsm_cleanup_mux		-	generic GSM protocol cleanup
  *	@gsm: our mux
@@ -3131,6 +3282,9 @@ static void gsm_cleanup_mux(struct gsm_mux *gsm, bool disc)
 	list_for_each_entry_safe(txq, ntxq, &gsm->tx_data_list, list)
 		kfree(txq);
 	INIT_LIST_HEAD(&gsm->tx_data_list);
+
+	if (gsm->proc)
+		proc_remove(gsm->proc);
 }
 
 /**
@@ -3145,6 +3299,7 @@ static void gsm_cleanup_mux(struct gsm_mux *gsm, bool disc)
 static int gsm_activate_mux(struct gsm_mux *gsm)
 {
 	struct gsm_dlci *dlci;
+	char pbuf[8];
 	int ret;
 
 	dlci = gsm_dlci_alloc(gsm, 0);
@@ -3162,6 +3317,9 @@ static int gsm_activate_mux(struct gsm_mux *gsm)
 
 	gsm->has_devices = true;
 	gsm->dead = false;		/* Tty opens are now permissible */
+
+	if (proc_gsm && snprintf(pbuf, sizeof(pbuf), "mux%u", gsm->num) > 0)
+		gsm->proc = proc_create_data(pbuf, 0444, proc_gsm, &gsm_proc_ops, gsm);
 	return 0;
 }
 
@@ -3596,6 +3754,8 @@ static void gsmld_close(struct tty_struct *tty)
 {
 	struct gsm_mux *gsm = tty->disc_data;
 
+	mutex_lock(&gsm_mux_mutex);
+
 	/* The ldisc locks and closes the port before calling our close. This
 	 * means we have no way to do a proper disconnect. We will not bother
 	 * to do one.
@@ -3607,6 +3767,8 @@ static void gsmld_close(struct tty_struct *tty)
 	gsmld_flush_buffer(tty);
 	/* Do other clean up here */
 	mux_put(gsm);
+
+	mutex_unlock(&gsm_mux_mutex);
 }
 
 /**
@@ -3622,14 +3784,20 @@ static void gsmld_close(struct tty_struct *tty)
 static int gsmld_open(struct tty_struct *tty)
 {
 	struct gsm_mux *gsm;
+	int ret = 0;
 
-	if (tty->ops->write == NULL)
-		return -EINVAL;
+	mutex_lock(&gsm_mux_mutex);
+	if (tty->ops->write == NULL) {
+		ret = -EINVAL;
+		goto err_unlock;
+	}
 
 	/* Attach our ldisc data */
 	gsm = gsm_alloc_mux();
-	if (gsm == NULL)
-		return -ENOMEM;
+	if (gsm == NULL) {
+		ret = -ENOMEM;
+		goto err_unlock;
+	}
 
 	tty->disc_data = gsm;
 	tty->receive_room = 65536;
@@ -3645,7 +3813,9 @@ static int gsmld_open(struct tty_struct *tty)
 	else
 		gsm->receive = gsm1_receive;
 
-	return 0;
+err_unlock:
+	mutex_unlock(&gsm_mux_mutex);
+	return ret;
 }
 
 /**
@@ -3769,17 +3939,24 @@ static int gsmld_ioctl(struct tty_struct *tty, unsigned int cmd,
 	struct gsm_mux *gsm = tty->disc_data;
 	unsigned int base, addr;
 	struct gsm_dlci *dlci;
+	int ret = 0;
 
 	switch (cmd) {
 	case GSMIOC_GETCONF:
 		gsm_copy_config_values(gsm, &c);
+		mutex_lock(&gsm_mux_mutex);
 		if (copy_to_user((void __user *)arg, &c, sizeof(c)))
-			return -EFAULT;
-		return 0;
+			ret = -EFAULT;
+		mutex_unlock(&gsm_mux_mutex);
+		break;
 	case GSMIOC_SETCONF:
+		mutex_lock(&gsm_mux_mutex);
 		if (copy_from_user(&c, (void __user *)arg, sizeof(c)))
-			return -EFAULT;
-		return gsm_config(gsm, &c);
+			ret = -EFAULT;
+		else
+			ret = gsm_config(gsm, &c);
+		mutex_unlock(&gsm_mux_mutex);
+		break;
 	case GSMIOC_GETFIRST:
 		base = mux_num_to_base(gsm);
 		return put_user(base + 1, (__u32 __user *)arg);
@@ -3824,6 +4001,7 @@ static int gsmld_ioctl(struct tty_struct *tty, unsigned int cmd,
 	default:
 		return n_tty_ioctl_helper(tty, cmd, arg);
 	}
+	return ret;
 }
 
 /*
@@ -4497,7 +4675,9 @@ static void gsmtty_cleanup(struct tty_struct *tty)
 
 	dlci_put(dlci);
 	dlci_put(gsm->dlci[0]);
+	mutex_lock(&gsm_mux_mutex);
 	mux_put(gsm);
+	mutex_unlock(&gsm_mux_mutex);
 }
 
 /* Virtual ttys for the demux */
@@ -4556,6 +4736,9 @@ static int __init gsm_init(void)
 		status = -EBUSY;
 		goto err_put_driver;
 	}
+
+	proc_gsm = proc_mkdir_mode("tty/ldisc/n_gsm", 0555, NULL);
+
 	pr_debug("gsm_init: loaded as %d,%d.\n",
 			gsm_tty_driver->major, gsm_tty_driver->minor_start);
 	return 0;
@@ -4569,6 +4752,8 @@ static int __init gsm_init(void)
 static void __exit gsm_exit(void)
 {
 	tty_unregister_ldisc(&tty_ldisc_packet);
+	if (proc_gsm)
+		proc_remove(proc_gsm);
 	tty_unregister_driver(gsm_tty_driver);
 	tty_driver_kref_put(gsm_tty_driver);
 }
-- 
2.34.1

[PATCH v5 10/10] tty: n_gsm: add restart flag to extended ioctl config

[D. Starke]

From: Daniel Starke <daniel.starke@siemens.com>

Currently, changing the parameters of the n_gsm mux gives no direct control
to the user whether this should trigger a mux reset or not. The decision is
solely made by the driver based on the assumption which parameter changes
are compatible or not. Therefore, the user has no means to perform an
automatic mux reset after parameter configuration for non-conflicting
changes.

Add the parameter 'flags' to 'gsm_config_ext' to force a mux reset after
ioctl setting regardless of whether the changes made require this or not
by setting this to 'GSM_FL_RESTART'. This is done similar to
'GSM_FL_RESTART' in gsm_dlci_config.flags.

Note that 'GSM_FL_RESTART' is currently the only allowed flag to allow
additions here.

Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
---
 drivers/tty/n_gsm.c         | 23 +++++++++++++++++++++++
 include/uapi/linux/gsmmux.h |  5 ++++-
 2 files changed, 27 insertions(+), 1 deletion(-)

v4 -> v5:
Newly added patch. This adds the missing equivalent from
struct gsm_dlci_config to struct gsm_config_ext.
See also the link below regarding the initial remark for this.

Please note that I cannot response to emails until August 7th. Felix Haase
will take over from our side for questions regarding this patch series or
the n_gsm.

Link: https://lore.kernel.org/all/cd7c33c8-2634-382d-cf62-3785e391af2@linux.intel.com/

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 30f73ab2491f..362a42bdc072 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -3578,6 +3578,7 @@ static void gsm_copy_config_ext_values(struct gsm_mux *gsm,
 
 static int gsm_config_ext(struct gsm_mux *gsm, struct gsm_config_ext *ce)
 {
+	bool need_restart = false;
 	unsigned int i;
 
 	/*
@@ -3587,6 +3588,20 @@ static int gsm_config_ext(struct gsm_mux *gsm, struct gsm_config_ext *ce)
 	for (i = 0; i < ARRAY_SIZE(ce->reserved); i++)
 		if (ce->reserved[i])
 			return -EINVAL;
+	if (ce->flags & ~GSM_FL_RESTART)
+		return -EINVAL;
+
+	/* Requires care */
+	if (ce->flags & GSM_FL_RESTART)
+		need_restart = true;
+
+	/*
+	 * Close down what is needed, restart and initiate the new
+	 * configuration. On the first time there is no DLCI[0]
+	 * and closing or cleaning up is not necessary.
+	 */
+	if (need_restart)
+		gsm_cleanup_mux(gsm, true);
 
 	/*
 	 * Setup the new configuration values
@@ -3594,6 +3609,14 @@ static int gsm_config_ext(struct gsm_mux *gsm, struct gsm_config_ext *ce)
 	gsm->wait_config = ce->wait_config ? true : false;
 	gsm->keep_alive = ce->keep_alive;
 
+	if (gsm->dead) {
+		int ret = gsm_activate_mux(gsm);
+		if (ret)
+			return ret;
+		if (gsm->initiator)
+			gsm_dlci_begin_open(gsm->dlci[0]);
+	}
+
 	return 0;
 }
 
diff --git a/include/uapi/linux/gsmmux.h b/include/uapi/linux/gsmmux.h
index 3bd6f03a8293..4c878d84dbda 100644
--- a/include/uapi/linux/gsmmux.h
+++ b/include/uapi/linux/gsmmux.h
@@ -11,6 +11,7 @@
  * flags definition for n_gsm
  *
  * Used by:
+ * struct gsm_config_ext.flags
  * struct gsm_dlci_config.flags
  */
 /* Forces a DLCI reset if set. Otherwise, a DLCI reset is only done if
@@ -98,12 +99,14 @@ struct gsm_netconfig {
  *
  * @keep_alive:  Control channel keep-alive in 1/100th of a second (0 to disable).
  * @wait_config: Wait for DLCI config before opening virtual link?
+ * @flags:       Mux specific flags.
  * @reserved:    For future use, must be initialized to zero.
  */
 struct gsm_config_ext {
 	__u32 keep_alive;
 	__u32 wait_config;
-	__u32 reserved[6];
+	__u32 flags;
+	__u32 reserved[5];
 };
 
 #define GSMIOC_GETCONF_EXT	_IOR('G', 5, struct gsm_config_ext)
-- 
2.34.1

Re: [PATCH v5 01/10] tty: n_gsm: add restart flag to DLC specific ioctl config

[Greg KH]

On Wed, May 17, 2023 at 05:56:55PM +0200, D. Starke wrote:
> From: Daniel Starke <daniel.starke@siemens.com>
> 
> Currently, changing the parameters of a DLCI gives no direct control to the
> user whether this should trigger a channel reset or not. The decision is
> solely made by the driver based on the assumption which parameter changes
> are compatible or not. Therefore, the user has no means to perform an
> automatic channel reset after parameter configuration for non-conflicting
> changes.
> 
> Add the parameter 'flags' to 'gsm_dlci_config' to force a channel reset
> after ioctl setting regardless of whether the changes made require this or
> not by setting this to 'GSM_FL_RESTART'.
> 
> Note that 'GSM_FL_RESTART' is currently the only allow flag to allow
> additions here.
> 
> Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
> ---
>  drivers/tty/n_gsm.c         |  4 ++++
>  include/uapi/linux/gsmmux.h | 15 ++++++++++++++-
>  2 files changed, 18 insertions(+), 1 deletion(-)
> 
> v4 -> v5:
> Changed GSM_FL_RESTART comment to be more specific about its use as
> suggested in the review comment.
> 
> Please note that I cannot response to emails until August 7th. Felix Haase
> will take over from our side for questions regarding this patch series or
> the n_gsm.
> 
> Link: https://lore.kernel.org/all/DB9PR10MB5881B63FBBA7912DF5A7A6A8E0789@DB9PR10MB5881.EURPRD10.PROD.OUTLOOK.COM/

Ok, I'll wait for a resend by Felix to consider these as having someone
be responsible for them if they cause problems is key :)

thanks,

greg k-h

Re: [PATCH v5 09/10] tty: n_gsm: expose configuration and statistics via proc fs

[Greg KH]

On Wed, May 17, 2023 at 05:57:03PM +0200, D. Starke wrote:
> From: Daniel Starke <daniel.starke@siemens.com>
> 
> The n_gsm mux collects various statistics about the mux and its channels.
> These are currently not exposed to the user. There exists already a proc fs
> path for tty ldiscs (/proc/tty/ldisc).
> 
> Extend this path by an 'n_gsm' node and create a proc file for each mux
> instance if active. The file exposes protocol statistics and channel states
> and configuration to the user. Mutex based locks are introduced to avoid
> inconsistent states.
> 
> The following shows an example output:
>  tty:ttyS1 flags:
>  initiator:1 mode:1 mru:64 mtu:64 t1:10 t2:34 t3:10 n2:3 k:2 wc:0 ka:100
>  bad_fcs:0 malformed:0 io_error:0 open_error:0 bad_size:0 unsupported:0
> 
>  dlci:0 state:OPEN cl:2 prio:0 i:UIH k:2 mtu:64 tx:35 rx:35
> 
> Description:
> tty:         The underlying device used by this mux.
> flags:       Tty flags relevant to the mux protocol.
> initiator:   0 for responder, 1 for initiator.
> mode:        0 for basic option mode, 1 for advanced option mode
> mru:         Maximum receive unit size.
> mtu:         Maximum transmission unit size.
> t1:          Acknowledgment timer.
> t2:          Response timer for multiplexer control channel.
> t3:          Response timer for wake-up procedure.
> n2:          Maximum number of retransmissions.
> k:           Window size.
> wc:          Wait for configuration before starting parameter negotiation?
> ka:          Control channel keep-alive timer (0 if disabled).
> bad_fcs:     Number of bad FCS.
> malformed:   Number of malformed frames.
> io_error:    Number of I/O errors on the underlying tty.
> open_error:  Number of failed DLCI open attempts.
> bad_size:    Number of n_gsm frames with bad size.
> unsupported: Number of malformed control frames.
> dlci:        Related channel number.
> state:       Current channel state. Possible values are CLOSED,
>              WAITING_CONFIG, CONFIGURE, OPENING, OPEN and CLOSING.
> cl:          Convergence layer type.
> prio:        Priority.
> i:           Framing. Possible values are UI and UIH.
> k:           Window size.
> mtu:         Maximum transmission unit size.
> tx:          Transmitted payload size in bytes (incl. convergence layer
>              type header).
> rx:          Received payload size in bytes (incl. convergence layer type
>              header).
> 
> All timers are in 1/100th of a second units.

Please no, procfs is NOT for driver/device statistics like this, that's
what sysfs is for if you really need/want it.

What userspace tool is going to read/parse this thing?  Where does it
live?

And what about the security issues involved with all of this new data
that you are now exposing to all users?  Has it been audited to verify
that it is safe to do so?

thanks,

greg k-h

RE: [PATCH v5 09/10] tty: n_gsm: expose configuration and statistics via proc fs

[Starke, Daniel]

> Please no, procfs is NOT for driver/device statistics like this, that's
> what sysfs is for if you really need/want it.
> 
> What userspace tool is going to read/parse this thing?  Where does it
> live?
> 
> And what about the security issues involved with all of this new data
> that you are now exposing to all users?  Has it been audited to verify
> that it is safe to do so?

Thank you for the feedback and patience. I understand your concerns.
Therefore, please proceed with this patch series by excluding this
patch #9. Please let me know if you need me to resend the patch series.

Best regards,
Daniel Starke

Re: [PATCH v5 09/10] tty: n_gsm: expose configuration and statistics via proc fs

[Greg KH]

On Wed, Aug 16, 2023 at 04:51:06AM +0000, Starke, Daniel wrote:
> > Please no, procfs is NOT for driver/device statistics like this, that's
> > what sysfs is for if you really need/want it.
> > 
> > What userspace tool is going to read/parse this thing?  Where does it
> > live?
> > 
> > And what about the security issues involved with all of this new data
> > that you are now exposing to all users?  Has it been audited to verify
> > that it is safe to do so?
> 
> Thank you for the feedback and patience. I understand your concerns.
> Therefore, please proceed with this patch series by excluding this
> patch #9. Please let me know if you need me to resend the patch series.

You have to resend them, they are long gone from my review queue, and
picking out an individual patch to not apply is difficult with our
existing tools as that is not a normal workflow.

thanks,

greg k-h