tty: n_gsm: add parameters used with parameter negotiation

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@siemens.com>
Link: https://lore.kernel.org/r/20221103091743.2119-2-daniel.starke@siemens.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 570c40a3d78f20ba0bb736b00fbec2562420e302..c217013b3e164c6ad0e28deac65f7e4be4f9c070 100644 (file)
--- 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);