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tty: n_gsm: introduce macro for minimal unit size 

n_gsm has a minimal protocol overhead of 7 bytes. The current code already
checks whether the configured MRU/MTU size is at least one byte more than
this.

Introduce the macro MIN_MTU to make this value more obvious.

Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
Link: https://lore.kernel.org/r/20221103091743.2119-1-daniel.starke@siemens.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Daniel Starke 2022-11-03 10:17:41 +01:00 committed by Greg Kroah-Hartman
parent d85bf51058
commit 7a1212475f
1 changed files with 5 additions and 2 deletions
drivers/tty
n_gsm.c

7
drivers/tty/n_gsm.c
View File

@ -89,6 +89,7 @@ module_param(debug, int, 0600);
*/
#define MAX_MRU 1500
#define MAX_MTU 1500
#define MIN_MTU (PROT_OVERHEAD + 1)
/* SOF, ADDR, CTRL, LEN1, LEN2, ..., FCS, EOF */
#define PROT_OVERHEAD 7
#define GSM_NET_TX_TIMEOUT (HZ*10)
@ -2712,7 +2713,9 @@ static int gsm_config(struct gsm_mux *gsm, struct gsm_config *c)
if ((c->adaption != 1 && c->adaption != 2) || c->k)
return -EOPNOTSUPP;
/* Check the MRU/MTU range looks sane */
if (c->mru > MAX_MRU || c->mtu > MAX_MTU || c->mru < 8 || c->mtu < 8)
if (c->mru < MIN_MTU || c->mtu < MIN_MTU)
return -EINVAL;
if (c->mru > MAX_MRU || c->mtu > MAX_MTU)
return -EINVAL;
if (c->n2 > 255)
return -EINVAL;
@ -3296,7 +3299,7 @@ static int gsm_create_network(struct gsm_dlci *dlci, struct gsm_netconfig *nc)
return -ENOMEM;
}
net->mtu = dlci->gsm->mtu;
net->min_mtu = 8;
net->min_mtu = MIN_MTU;
net->max_mtu = dlci->gsm->mtu;
mux_net = netdev_priv(net);
mux_net->dlci = dlci;