[PATCH v4 1/8] tty: n_gsm: add restart flag to DLC specific ioctl config

[PATCH v4 1/8] 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 | 13 ++++++++++++-
 2 files changed, 16 insertions(+), 1 deletion(-)

v3 -> v4:
Changed gsm_dlci_config field name from 'restart' to 'flags' and introduced
'GSM_FL_RESTART' to set the restart flag. The patch description was changed
accordingly. This was done as suggested during the review.
The remarked kernel doc compatible field comment is done in patch 2/8.

Link: https://lore.kernel.org/all/2023042453-dubbed-botany-2ed9@gregkh/

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..958257af05ab 100644
--- a/include/uapi/linux/gsmmux.h
+++ b/include/uapi/linux/gsmmux.h
@@ -2,10 +2,20 @@
 #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
+ */
+/* Force DLCI channel reset? Always cleared on retrieval. */
+#define GSM_FL_RESTART	_BITUL(0)
+
 struct gsm_config
 {
 	unsigned int adaption;
@@ -58,7 +68,8 @@ 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 v4 2/8] 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(-)

v3 -> v4:
Changed comments of all other structs in gsmmux.h to kernel doc format as
suggested during review. The patch description and subject was changed to
match this.

Link: https://lore.kernel.org/all/2023042438-whole-cannot-1945@gregkh/
Link: https://lore.kernel.org/all/20230424075251.5216-2-daniel.starke@siemens.com/

diff --git a/include/uapi/linux/gsmmux.h b/include/uapi/linux/gsmmux.h
index 958257af05ab..54bc8767bd75 100644
--- a/include/uapi/linux/gsmmux.h
+++ b/include/uapi/linux/gsmmux.h
@@ -16,6 +16,28 @@
 /* Force DLCI channel reset? Always cleared on retrieval. */
 #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;
@@ -29,18 +51,32 @@ 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)
@@ -49,27 +85,55 @@ 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 v4 3/8] 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(-)

v3 -> v4:
No changes.

Link: https://lore.kernel.org/all/20230424075251.5216-3-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 v4 4/8] 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(-)

v3 -> v4:
No changes.

Link: https://lore.kernel.org/all/20230424075251.5216-4-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 v4 5/8] 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(-)

v3 -> v4:
No changes.

Link: https://lore.kernel.org/all/20230424075251.5216-5-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 v4 6/8] 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(+)

v3 -> v4:
No changes.

Link: https://lore.kernel.org/all/20230424075251.5216-6-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 v4 7/8] 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(-)

v3 -> v4:
No changes.

Link: https://lore.kernel.org/all/20230424075251.5216-7-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 v4 8/8] 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 | 25 ++++++++++++++++++++++++-
 1 file changed, 24 insertions(+), 1 deletion(-)

v3 -> v4:
No changes.

Link: https://lore.kernel.org/all/20230424075251.5216-8-daniel.starke@siemens.com/

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 62bff4474b57..2e2e1dafcf40 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -186,6 +186,9 @@ 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 +1219,7 @@ 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 +1287,7 @@ 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 +1466,7 @@ 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 +1494,7 @@ 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 +1859,13 @@ 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 +1944,8 @@ 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 +2310,9 @@ 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 +2345,9 @@ 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 +2367,9 @@ 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 +2446,7 @@ 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 +2807,7 @@ 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

Re: [PATCH v4 1/8] tty: n_gsm: add restart flag to DLC specific ioctl config

[Greg KH]

On Wed, Apr 26, 2023 at 10:03:08AM +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 | 13 ++++++++++++-
>  2 files changed, 16 insertions(+), 1 deletion(-)
> 
> v3 -> v4:
> Changed gsm_dlci_config field name from 'restart' to 'flags' and introduced
> 'GSM_FL_RESTART' to set the restart flag. The patch description was changed
> accordingly. This was done as suggested during the review.
> The remarked kernel doc compatible field comment is done in patch 2/8.
> 
> Link: https://lore.kernel.org/all/2023042453-dubbed-botany-2ed9@gregkh/
> 
> 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..958257af05ab 100644
> --- a/include/uapi/linux/gsmmux.h
> +++ b/include/uapi/linux/gsmmux.h
> @@ -2,10 +2,20 @@
>  #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
> + */
> +/* Force DLCI channel reset? Always cleared on retrieval. */

I do not understand this comment, sorry.  What question are you asking?
What happens if it is set?  What happens if it is not set?  More
documentation is always good, especially for new user/kernel apis that
are not documented anywhere else.

thanks,

greg k-h

Re: [PATCH v4 8/8] tty: n_gsm: add DLCI specific rx/tx statistics

[Greg KH]

On Wed, Apr 26, 2023 at 10:03:15AM +0200, D. Starke wrote:
> 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.

As this is patch 8/8, "upcoming patch" makes no sense, sorry.  Please
either drop this and add it as part of the series that provides this
functionality, or add the functionality to the patch series as the next
patch in it.

> 
> Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
> ---
>  drivers/tty/n_gsm.c | 25 ++++++++++++++++++++++++-
>  1 file changed, 24 insertions(+), 1 deletion(-)
> 
> v3 -> v4:
> No changes.
> 
> Link: https://lore.kernel.org/all/20230424075251.5216-8-daniel.starke@siemens.com/
> 
> diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
> index 62bff4474b57..2e2e1dafcf40 100644
> --- a/drivers/tty/n_gsm.c
> +++ b/drivers/tty/n_gsm.c
> @@ -186,6 +186,9 @@ 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) */

No blank line before this?

And why isn't this structure documented in kerneldoc to make it more
obvious what is happening?

thanks,

greg k-h

RE: [PATCH v4 1/8] tty: n_gsm: add restart flag to DLC specific ioctl config

[Starke, Daniel]

> > +/* Force DLCI channel reset? Always cleared on retrieval. */
> 
> I do not understand this comment, sorry.  What question are you asking?
> What happens if it is set?  What happens if it is not set?  More
> documentation is always good, especially for new user/kernel apis that
> are not documented anywhere else.

Ok, I will rephrase it to be more explicit about it.

Best regards,
Daniel Starke

RE: [PATCH v4 8/8] tty: n_gsm: add DLCI specific rx/tx statistics

[Starke, Daniel]

> > 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.
> 
> As this is patch 8/8, "upcoming patch" makes no sense, sorry.  Please
> either drop this and add it as part of the series that provides this
> functionality, or add the functionality to the patch series as the next
> patch in it.

I will add the remaining two outstanding patches on my side to this patch
series. The functional addition which exposes these values to the user is
included there.

> > diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
> > index 62bff4474b57..2e2e1dafcf40 100644
> > --- a/drivers/tty/n_gsm.c
> > +++ b/drivers/tty/n_gsm.c
> > @@ -186,6 +186,9 @@ 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) */
> 
> No blank line before this?

I will add a blank line before this one.

> 
> And why isn't this structure documented in kerneldoc to make it more
> obvious what is happening?

True, it would be better if this was the case. However, there was no such
cleanup of this internal structure yet and this is out of scope of this
patch/patch series. A future patch needs to fix this.


Best regards,
Daniel Starke