[PATCH v2 2/3] tty: n_gsm: add parameters used with parameter negotiation

From: D. Starke
Date: Mon Oct 24 2022 - 17:18:09 EST


From: Daniel Starke <daniel.starke@xxxxxxxxxxx>

n_gsm is based on the 3GPP 07.010 and its newer version is the 3GPP 27.010.
See https://portal.3gpp.org/desktopmodules/Specifications/SpecificationDetails.aspx?specificationId=1516
The changes from 07.010 to 27.010 are non-functional. Therefore, I refer to
the newer 27.010 here. Chapter 5.4.6.3.1 describes the encoding of the
parameter negotiation messages.

Add the parameters used there to 'gsm_mux' and 'gsm_dlci' and initialize both
according to the value ranges and recommended defaults defined in chapter 5.7.

Replace the use of the DLC default values from the 'gsm_mux' fields with the DLC
specific values from the 'gsm_dlci' fields where applicable.

Signed-off-by: Daniel Starke <daniel.starke@xxxxxxxxxxx>
---
drivers/tty/n_gsm.c | 58 +++++++++++++++++++++++++++++++++++----------
1 file changed, 45 insertions(+), 13 deletions(-)

v1 -> v2:
Incorporated review comments.
Changed type of t3 in gsm_mux to unsigned int.

Link: https://lore.kernel.org/all/4519259-1e70-351c-756c-57c1e665e94@xxxxxxxxxxxxxxx/

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 570c40a3d78f..c217013b3e16 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -40,6 +40,7 @@
#include <linux/tty.h>
#include <linux/ctype.h>
#include <linux/mm.h>
+#include <linux/math.h>
#include <linux/string.h>
#include <linux/slab.h>
#include <linux/poll.h>
@@ -75,7 +76,12 @@ module_param(debug, int, 0600);

#define T1 10 /* 100mS */
#define T2 34 /* 333mS */
+#define T3 10 /* 10s */
#define N2 3 /* Retry 3 times */
+#define K 2 /* outstanding I frames */
+
+#define MAX_T3 255 /* In seconds. */
+#define MAX_WINDOW_SIZE 7 /* Limit of K in error recovery mode. */

/* Use long timers for testing at low speed with debug on */
#ifdef DEBUG_TIMING
@@ -160,7 +166,12 @@ struct gsm_dlci {
int prev_adaption;
u32 modem_rx; /* Our incoming virtual modem lines */
u32 modem_tx; /* Our outgoing modem lines */
+ unsigned int mtu;
bool dead; /* Refuse re-open */
+ /* Configuration */
+ u8 prio; /* Priority */
+ u8 ftype; /* Frame type */
+ u8 k; /* Window size */
/* Flow control */
bool throttled; /* Private copy of throttle state */
bool constipated; /* Throttle status for outgoing */
@@ -283,7 +294,9 @@ struct gsm_mux {
int adaption; /* 1 or 2 supported */
u8 ftype; /* UI or UIH */
int t1, t2; /* Timers in 1/100th of a sec */
+ unsigned int t3; /* Power wake-up timer in seconds. */
int n2; /* Retry count */
+ u8 k; /* Window size */

/* Statistics (not currently exposed) */
unsigned long bad_fcs;
@@ -1075,12 +1088,12 @@ static int gsm_dlci_data_output(struct gsm_mux *gsm, struct gsm_dlci *dlci)
return 0;

/* MTU/MRU count only the data bits but watch adaption mode */
- if ((len + h) > gsm->mtu)
- len = gsm->mtu - h;
+ if ((len + h) > dlci->mtu)
+ len = dlci->mtu - h;

size = len + h;

- msg = gsm_data_alloc(gsm, dlci->addr, size, gsm->ftype);
+ msg = gsm_data_alloc(gsm, dlci->addr, size, dlci->ftype);
if (!msg)
return -ENOMEM;
dp = msg->data;
@@ -1144,19 +1157,19 @@ static int gsm_dlci_data_output_framed(struct gsm_mux *gsm,
len = dlci->skb->len + overhead;

/* MTU/MRU count only the data bits */
- if (len > gsm->mtu) {
+ if (len > dlci->mtu) {
if (dlci->adaption == 3) {
/* Over long frame, bin it */
dev_kfree_skb_any(dlci->skb);
dlci->skb = NULL;
return 0;
}
- len = gsm->mtu;
+ len = dlci->mtu;
} else
last = 1;

size = len + overhead;
- msg = gsm_data_alloc(gsm, dlci->addr, size, gsm->ftype);
+ msg = gsm_data_alloc(gsm, dlci->addr, size, dlci->ftype);
if (msg == NULL) {
skb_queue_tail(&dlci->skb_list, dlci->skb);
dlci->skb = NULL;
@@ -1213,7 +1226,7 @@ static int gsm_dlci_modem_output(struct gsm_mux *gsm, struct gsm_dlci *dlci,
return -EINVAL;
}

- msg = gsm_data_alloc(gsm, dlci->addr, size, gsm->ftype);
+ msg = gsm_data_alloc(gsm, dlci->addr, size, dlci->ftype);
if (!msg) {
pr_err("%s: gsm_data_alloc error", __func__);
return -ENOMEM;
@@ -1338,8 +1351,9 @@ static void gsm_dlci_data_kick(struct gsm_dlci *dlci)
static int gsm_control_command(struct gsm_mux *gsm, int cmd, const u8 *data,
int dlen)
{
- struct gsm_msg *msg = gsm_data_alloc(gsm, 0, dlen + 2, gsm->ftype);
+ struct gsm_msg *msg;

+ msg = gsm_data_alloc(gsm, 0, dlen + 2, gsm->dlci[0]->ftype);
if (msg == NULL)
return -ENOMEM;

@@ -1365,7 +1379,8 @@ static void gsm_control_reply(struct gsm_mux *gsm, int cmd, const u8 *data,
int dlen)
{
struct gsm_msg *msg;
- msg = gsm_data_alloc(gsm, 0, dlen + 2, gsm->ftype);
+
+ msg = gsm_data_alloc(gsm, 0, dlen + 2, gsm->dlci[0]->ftype);
if (msg == NULL)
return;
msg->data[0] = (cmd & 0xFE) << 1 | EA; /* Clear C/R */
@@ -2075,6 +2090,13 @@ static struct gsm_dlci *gsm_dlci_alloc(struct gsm_mux *gsm, int addr)
dlci->gsm = gsm;
dlci->addr = addr;
dlci->adaption = gsm->adaption;
+ dlci->mtu = gsm->mtu;
+ if (addr == 0)
+ dlci->prio = 0;
+ else
+ dlci->prio = roundup(addr + 1, 8) - 1;
+ dlci->ftype = gsm->ftype;
+ dlci->k = gsm->k;
dlci->state = DLCI_CLOSED;
if (addr) {
dlci->data = gsm_dlci_data;
@@ -2650,7 +2672,9 @@ static struct gsm_mux *gsm_alloc_mux(void)

gsm->t1 = T1;
gsm->t2 = T2;
+ gsm->t3 = T3;
gsm->n2 = N2;
+ gsm->k = K;
gsm->ftype = UIH;
gsm->adaption = 1;
gsm->encoding = GSM_ADV_OPT;
@@ -2691,7 +2715,7 @@ static void gsm_copy_config_values(struct gsm_mux *gsm,
c->initiator = gsm->initiator;
c->t1 = gsm->t1;
c->t2 = gsm->t2;
- c->t3 = 0; /* Not supported */
+ c->t3 = gsm->t3;
c->n2 = gsm->n2;
if (gsm->ftype == UIH)
c->i = 1;
@@ -2700,7 +2724,7 @@ static void gsm_copy_config_values(struct gsm_mux *gsm,
pr_debug("Ftype %d i %d\n", gsm->ftype, c->i);
c->mru = gsm->mru;
c->mtu = gsm->mtu;
- c->k = 0;
+ c->k = gsm->k;
}

static int gsm_config(struct gsm_mux *gsm, struct gsm_config *c)
@@ -2717,12 +2741,16 @@ static int gsm_config(struct gsm_mux *gsm, struct gsm_config *c)
return -EINVAL;
if (c->mru > MAX_MRU || c->mtu > MAX_MTU)
return -EINVAL;
+ if (c->t3 > MAX_T3)
+ return -EINVAL;
if (c->n2 > 255)
return -EINVAL;
if (c->encapsulation > 1) /* Basic, advanced, no I */
return -EINVAL;
if (c->initiator > 1)
return -EINVAL;
+ if (c->k > MAX_WINDOW_SIZE)
+ return -EINVAL;
if (c->i == 0 || c->i > 2) /* UIH and UI only */
return -EINVAL;
/*
@@ -2770,6 +2798,10 @@ static int gsm_config(struct gsm_mux *gsm, struct gsm_config *c)
gsm->t1 = c->t1;
if (c->t2)
gsm->t2 = c->t2;
+ if (c->t3)
+ gsm->t3 = c->t3;
+ if (c->k)
+ gsm->k = c->k;

/*
* FIXME: We need to separate activation/deactivation from adding
@@ -3298,9 +3330,9 @@ static int gsm_create_network(struct gsm_dlci *dlci, struct gsm_netconfig *nc)
pr_err("alloc_netdev failed\n");
return -ENOMEM;
}
- net->mtu = dlci->gsm->mtu;
+ net->mtu = dlci->mtu;
net->min_mtu = MIN_MTU;
- net->max_mtu = dlci->gsm->mtu;
+ net->max_mtu = dlci->mtu;
mux_net = netdev_priv(net);
mux_net->dlci = dlci;
kref_init(&mux_net->ref);
--
2.34.1